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Cold-water coral growth in the Alboran Sea related to high productivity during the Late Pleistocene and Holocene
Supplementary resource (1)
Data
January 2013
... CWCs are most abundant at depths shallower than 1500 m and within water masses that display salinity values around 35 PSU and temperatures between 4 and 14 • C (Freiwald, 2002;Freiwald et al., 2004;Roberts et al., 2006;Davies and Guinotte, 2011;Flögel et al., 2014). Cold-water corals thrive in areas of enhanced primary productivity (White et al., 2005;Wienberg et al., 2010;Eisele et al., 2011;Fink et al., 2013Fink et al., , 2015Stalder et al., 2015Stalder et al., , 2018, whilst their development is driven by locally increased current velocity and turbulence, which increase food availability to the corals (i.e. higher particle encounter rates, resuspension of organic matter) White et al., 2005;Dorschel et al., 2007;Mienis et al., 2007;Davies et al., 2008). Under suitable environmental conditions, CWCs can form mounds comprised of CWC skeletons, embedded in a matrix of hemipelagic sediments that stabilize the structure (Foubert et al., 2008;Titschack et al., 2009;Thierens et al., 2010). ...
... The height of these buildups ranges from several to hundreds of metres, whereas their base can extend for several kilometres (De Mol et al., 2002;Huvenne et al., 2003;Dorschel et al., 2005;Wheeler et al., 2007). Large CWC mound provinces have for example been observed in the Northeast Atlantic off the coast of Ireland (De Mol et al., 2002;Huvenne et al., 2002;Wheeler et al., 2007;Van der Land et al., 2013), Norway (Freiwald, 2002;López Correa et al., 2012;Sneli, 2014), Morocco (Foubert et al., 2008;Wienberg et al., 2010;Hebbeln, 2019), Mauritania (Ramos et al., 2017;Wienberg et al., 2018), Mexico (Hebbeln et al., 2014;Matos et al., 2017), and in Mediterranean basins (Remia and Taviani, 2005;Freiwald et al., 2009;Comas and Pinheiro, 2007;Martorelli et al., 2011;Fink et al., 2013;Lo Iacono et al., 2014;Corbera et al., 2019;Angeletti et al., 2020;Camafort et al., 2020;Corbera et al., 2022). In the Northeast Atlantic Ocean and the Mediterranean Sea, the main framework building azooxanthellate scleractinian corals are Desmophyllum pertusum, formely known as Lophelia pertusa (Addamo et al., 2016), and Madrepora oculata (e.g. ...
... Documented CWC occurrences in the Mediterranean demonstrate that they mostly thrive during warm intervals (Fink et al., 2015 and references therein;Wang et al., 2019;Krengel, 2020;Corbera et al., 2021), although recent observations show that corals situated within the Tunisian Coral Mound Province experienced their most important growth phase during the last glacial period (Corbera et al., 2022). In the Mediterranean Sea, CWC mounds are found in the Alboran Sea (Comas and Pinheiro, 2007;Fink et al., 2013;Lo Iacono et al., 2014;Corbera et al., 2019;Hebbeln, 2019;Sánchez-Guillamón et al., 2022), on the Tunisian Plateau (Camafort et al., 2020;Corbera et al., 2022), the Strait of Sicily (Martorelli et al., 2011), in the northern Ionian Sea (Carlier et al., 2009;Freiwald et al., 2009) and in the Corsica Channel (Remia and Taviani, 2005;Angeletti et al., 2020). CWC mounds situated in the Alboran Sea are currently divided between those in the West and East Melilla Coral Provinces (WMCP and EMCP) off the coast of Melilla (Comas and Pinheiro, 2007;Fink et al., 2013;Lo Iacono et al., 2014), and those located on the Cabliers Bank (the Cabliers Coral Mound Province: CMP), which is ~40 km northeast of the EMCP (Schröder-Ritzrau et al., 2005;Pardo et al., 2011;Corbera et al., 2019;Fig. ...
The start-up, build-up and demise of cold-water coral mounds are governed by environmental changes at global, regional and local scales. Whilst the formation of cold-water coral mounds across the globe is widely documented to follow interglacial-glacial cycles, less is known about their response to local environmental fluctuations during short time intervals. This study investigates the local variations in coral mound build-up along Brittlestar Ridge I (East Melilla Coral Province, Southeast Alboran Sea) by comparing three on-mound gravity cores collected ~1 km apart, together with five previously described on-mound records, along a longitudinal transect on the ridge crest. Radiocarbon foraminiferal dating associated to U-series coral dating allowed to correlate the different records and to estimate mound aggradation rates, whilst grain-size analysis provided information on bottom current velocities. Prior to a rapid period of coral mound build-up initiated at ~14.75 ka BP, the three cores present an occurrence of cm-thick bryozoan-dominated intervals nearly entirely consisting of the erect cheleis-tome Buskea dichotoma. Offsets between benthic foraminiferal and coral ages suggest that older dead allochto-nous benthic foraminifera are possibly eroded from neighbouring settings, transported and deposited within the coral framework. In contrast, younger benthic foraminifera would develop on dead coral framework during periods of reef stagnation. The comparison of all cores indicates that mound build-up along the ridge did not follow the same timing during the last ~16 kyr and that mound aggradation was marked by a staggered dynamic. Both local differences in bottom current velocities and patchiness of other key environmental actors (e.g. sub-strate availability) are suspected to drive the observed staggered mound build-up. Cold-water coral mound build-up shows important differences during Greenland Interstadial 1 (i.e. the Bølling-Allerød) and the Holocene, hence examplifying how local environmental variability may overprint global and regional climate variability over short time periods.
... Spatial and temporal development of coral mounds reflect the conditions that have supported (or not) the proliferation of CWC (e.g., Bahr et al., 2020;Cyr et al., 2016;De Clippele et al., 2017b;De Haas et al., 2009;Douarin et al., 2013;Eisele et al., 2011;Fink et al., 2013;Frank et al., 2011;Hebbeln et al., 2019;Kano et al., 2010;Matos et al., 2017;Wienberg et al., 2010). ...
... As food supply is the most relevant condition for thriving CWC colonies, the development of coral mounds is controlled by the variability of primary productivity (e.g., Eisele et al., 2011;Fink et al., 2013;Wang et al., 2017;Wilson et al., 2014), and the hydrodynamic regime (e.g., Dorschel et al., 2005;Matos et al., 2017). These two parameters have a binding relationship to another control on CWC physiology: dissolved oxygen concentration (DO). ...
... 24, West Melilla (Lo Iacono et al., 2014). 25, East Melilla (Colman et al., 2005;Fink et al., 2013). 26, Cabliers (Corbera et al., 2019). ...
Over the last 25 years, extensive geological investigations on coral mounds, seafloor structures in the deep-sea built by ecosystem-engineering cold-water corals (CWC), have revealed that the spatial and temporal occurrences of CWC depend on environmental and climate conditions. Coral mounds in the NE Atlantic were the first and have been the most studied coral mound provinces (CMPs), providing the fundamental evidence of the environmental forcing supporting CWC and on the development of coral mounds over glacial-interglacial cycles. However, the continuous discovery of coral mounds under the extremely variable oceanographic conditions along the Atlantic margins have brought new evidence to re-discuss our previous knowledge on CWC and coral mounds.
This study was designed for one of the latest CMP discovered: the Namibian coral mounds. More than 2000 mounds are sitting on the Namibian inner shelf (~20°S) between 160-270 m water depths. The Namibian CMP occurs under an oceanographic setting controlled by the Benguela Upwelling System (BUS). The BUS is one of the large eastern-boundary upwelling systems with the highest primary production in the world ocean. Due to these highly productive conditions, shelf-bottom waters become severely oxygen-depleted resulting from the consumption of oxygen through the decomposition of organic matter. The Namibian coral mounds occur exactly at the core of the local oxygen minimum zone (OMZ, 160–270 m water depth), where dissolved oxygen concentrations (DO) are 0-0.5 mL L−1 and accompanied by relatively high potential temperatures of 12.4 to 13.4 °C which can already be critical for CWC physiology. These present-day conditions prevent any CWC proliferation, and indeed no living colonies have been observed during the dives of a remotely operated vehicle.
After the analysis and discussion of the present-day environmental condition (Manuscript I), this thesis aimed to identify how oceanographic conditions controlled the spatial-morphological variability (Manuscript II) and temporal development (Manuscript III) of the Namibian coral mounds. The results show that spatial distribution and morphometric appearance of the coral mounds is highly controlled by the interplay between the underlying topography (erosional features) and the hydrodynamic regime (internal tides). Moreover, U-series dating on CWC skeletons combined with local paleoceanographic reconstructions link the temporal development (4.5-9.5 kyr BP) of the Namibian coral mounds to a decrease of the BUS activity, with a consequent relative relaxation of the local OMZ. This likely brought DO values comparable to the present-day hypoxic conditions on the Angola CMP, where living CWC colonies have been observed.
The findings of this thesis show how a comprehensive geological investigation on coral mounds can reveal important insights on the life and demise of CWC. The methods applied and the results obtained might serve as framework for investigating new CMPs, as well stimulating re-analyses of older datasets acquired from well-known CMPs. Moreover, improving our knowledge on CWC, to which this study on the Namibian coral mounds contributed, will provide insights on the fate of CWC under the changing ocean and climate conditions in the future.
... In the Mediterranean Sea, the study of coral mound development in relation to paleoceanographic variations during the Pleistocene and Holocene is mainly concentrated on the CMPs in the southern Albor an Sea. Sediment cores obtained from these CMPs, all recorded a highly prolific period for CWCs starting during the last deglaciation (~14e15 ka) and lasting until the end of the Early Holocene (~8e9 ka), which resulted in mound development with remarkably high vertical mound aggradation rates (ARs) of 100e400 cm kyr À1 (Fink et al., 2013;Stalder et al. 2015Stalder et al. , 2018Wang et al., 2019;Fentimen et al., 2020;Corbera et al., 2021;Korpanty et al. submitted). This thriving phase has been ascribed to regional environmental conditions of enhanced (surface and export) productivity and moderate to strong hydrodynamics maintaining coral growth and sediment supply (Fink et al., 2013;Stalder et al., 2015;Fentimen et al., 2020;Portilho-Ramos et al., 2022). ...
... Sediment cores obtained from these CMPs, all recorded a highly prolific period for CWCs starting during the last deglaciation (~14e15 ka) and lasting until the end of the Early Holocene (~8e9 ka), which resulted in mound development with remarkably high vertical mound aggradation rates (ARs) of 100e400 cm kyr À1 (Fink et al., 2013;Stalder et al. 2015Stalder et al. , 2018Wang et al., 2019;Fentimen et al., 2020;Corbera et al., 2021;Korpanty et al. submitted). This thriving phase has been ascribed to regional environmental conditions of enhanced (surface and export) productivity and moderate to strong hydrodynamics maintaining coral growth and sediment supply (Fink et al., 2013;Stalder et al., 2015;Fentimen et al., 2020;Portilho-Ramos et al., 2022). Such conditions were most likely further supported by the activity of internal waves, which enhanced turbulence and increased the delivery of food and sediment particles at the interface between the Levantine Intermediate Water (LIW) and overlying Atlantic water (Wang et al., 2019;Corbera et al., 2021). ...
... The Mid-to Late Holocene mound development displayed a contrasting pattern. For both Melilla CMPs, mound development significantly reduced during the Holocene (Fink et al., 2013;Wang et al., 2019;Wienberg, 2019), while exceptionally thriving CWCs are found on some northern mounds of the Cabliers CMP until today (Corbera et al., 2021). Hence, the present-day reef status prevailing at the respective CMPs varies in close vicinity of 50e60 km from extinct reefs, to scattered and small live coral colonies and to thriving reefs (Hebbeln et al., 2009;Lo Iacono et al., 2014;Corbera et al., 2019). ...
This study presents sediment cores up to 70 m long collected by the sea floor drill rig MARUM-MeBo70 from cold-water coral mounds in the western Mediterranean Sea. From these cores, an unprecedented data set of 200 Th/U coral ages has been obtained, greatly expanding our knowledge of the evolution of Mediterranean coral mounds. The drill records provided new insights into the initiation of the Mediterranean coral mounds as the base of a 60-m-high mound was penetrated and dated to the Mid-Pleistocene (∼390 ka). We also found that mound initiation was non-synchronous as larger mounds possibly initiated already during the Mid-Pleistocene Transition. During the last 480 kyr, mound development occurred in short and intense pulses (duration: ∼10–30 kyr; aggradation rates: 20–275 cm kyr⁻¹), which could not be assigned to ice age-paced oscillations, but showed a remarkably coherent pattern with precession-driven changes in African hydroclimate. Increased dust supply, related to a desertification of the Sahara and northern Africa, appears to have boosted mound development by enhancing productivity conditions (to promote coral growth) and sediment supply (to promote mound aggradation). In addition, mound development is closely linked to the well-ventilated and nutrient-rich Levantine Intermediate Water and internal wave activity associated to this water mass that provided turbulent conditions and enhanced the lateral delivery of food and sediments. During African humid periods, increased freshwater input into the Mediterranean impaired the formation of Levantine Intermediate Water, which most likely resulted in low-energy and oxygen-depleted living conditions for Mediterranean coral communities. This study shows the importance to consider past changes in continental hydroclimate and their implications on oceanic processes to fully understand the complex environmental controls on coral mound development. In the Mediterranean Sea, such land-atmosphere-ocean feedback processes are especially amplified due to its latitudinal placement between two climate regimes, making this basin and its deep-sea ecosystems most vulnerable to past and future climate change.
... Consequently, CWC mounds can reach considerable heights of over 300 m and spread for kilometres in width and length at their base (De Mol et al., 2002;Kenyon et al., 2003;Huvenne et al., 2005). Mound development may span from thousands to millions of years and attain important mound aggradation rates, e.g. ± 400 cm kyr −1 in the East Melilla Coral Province (EMCP; Frank et al., 2009;López Correa et al., 2012;Fink et al., 2013;Stalder et al., 2015;Wienberg et al., 2018). As such, and in spite of mound formation being generally discontinuous, CWC mounds are valuable environmental and climate archives (Rüggeberg et al., 2007;Roberts et al., 2009). ...
... In the Mediterranean Sea, CWC mound provinces are concentrated in the Alboran Sea (Fink et al., 2013(Fink et al., , 2015Lo Iacono et al., 2014;Stalder et al., 2015Stalder et al., , 2018Terhzaz et al., 2018;Wang et al., 2019;Fentimen et al., 2020a;Rachid et al., 2020;Corbera et al., 2021;Sánchez-Guillamón et al., 2022), the Corsica Channel (Remia and Taviani, 2005;Angeletti et al., 2020), the Strait of Sicily (Martorelli et al., 2011), the northern Ionian Sea (Carlier et al., 2009;Freiwald et al., 2009), and on the Tunisian Plateau (Camafort et al., 2020;Corbera et al., 2022). Except for the North Cabliers Coral Mound Province situated in the central part of the eastern Alboran Sea (Fig. 1b), the northern Ionian Sea mounds (i.e. ...
... 1b). Within the EMCP, the localities of Brittlestar Ridge I (BRI) and Dragon Mound have received the most attention during the last decade (Fig. 1b and c;Fink et al., 2013Fink et al., , 2015Stalder et al., 2015Stalder et al., , 2018Terhzaz et al., 2018;Fentimen et al., 2020a;Krengel, 2020;Rachid et al., 2020;Wang et al., 2021). U-series dating of corals revealed that the formation of Dragon Mound began 450 kyr ago, whereas BRI started building up over 538 kyr ago (Krengel, 2020). ...
This study provides a detailed reconstruction of cold-water coral mound build-up within the East Melilla Coral Province (southeastern Alboran Sea), more precisely at the northern part of Brittlestar Ridge I, over the last 300 kyr. The multiproxy investigation of core MD13-3462G reveals that mound build-up took place during both interglacial and glacial periods at average aggradation rates ranging between 1 and 10 cm kyr−1. These observations imply that corals never thrived but rather developed under stressful environmental conditions. Maximum aggradation rates of 18 cm kyr−1 are recorded during the last glacial period, hence providing the first evidence of coral mound development during this time period in the western Mediterranean. The planktonic (Globigerina bulloides) and benthic (Lobatula lobatula) δ18O records from core MD13-3462G show typical interglacial–glacial variations during the last two interglacial–glacial cycles. This is in contrast with δ18O records generally recovered from coral mounds and highlights that the northern part of Brittlestar Ridge I experienced reduced albeit relatively continuous accretion. High abundances of infaunal benthic foraminifera (Bulimina marginata, Bulimina striata, and Uvigerina mediterranea) suggest that weak seafloor oxygenation associated with important terrestrial organic matter input characterized interglacial periods, whilst the dominance of large epibenthic species (Discanomalina coronata and Lobatula lobatula) and Miliolids is probably linked to stronger Levantine Intermediate Water circulation and fresher organic matter input during glacial periods. In addition, the computed tomography (CT) quantification of macrofaunal remains shows that the bryozoan Buskea dichotoma is present throughout the entire 300 kyr of mound build-up history, with the exception of MIS 5, and is possibly a key contributor to mound development during glacial periods. The comparison of our observations to other long-term coral mound records demonstrates that western and central Mediterranean coral mounds do not show concurrent build-up over interglacial–glacial cycles, implying that their development may be driven by regional and local environmental forcing.
... To assess the impact of changing paleoenvironmental conditions on the development of CWC ecosystems, we compiled well-documented records from 6 CWC sites in the North Atlantic and in the Mediterranean Sea revealing at least one major change (i.e., on-or offset) in CWC proliferation: (1) [53,54], and 2 sites in the Alboran Sea in the western Mediterranean Sea: (5) West Melilla [55] and (6) East Melilla [56][57][58]. In order to provide a comprehensive data set for all regions, we combined already published records with newly established data. ...
... Lophelia pertusa reoccurred in the Mediterranean Sea (Alboran Sea, West, and East Melilla coral mound provinces) with the onset of the Bølling-Allerød interstadial at around 14 kyr BP (Figs 2 and 3, S11 and S12 Figs) and remained most prolific until the Early Holocene. Afterward, it became progressively less abundant [56][57][58]61] and locally even completely disappeared (West Melilla: at approximately 5 kyr BP [55]). ...
... In the western Mediterranean Sea (Alboran Sea), L. pertusa was absent during the early deglacial period until it reoccurred at approximately 14 kyr BP (Figs 2 and 3, S11 and S12 Figs) [55,56,61]. The 2 known CWC ecosystems in the West and East Melilla coral mound provinces developed predominantly between approximately 14 kyr BP to 8 to 9 kyr BP [56][57][58]. ...
Cold-water corals (CWCs) are the engineers of complex ecosystems forming unique biodiversity hotspots in the deep sea. They are expected to suffer dramatically from future environmental changes in the oceans such as ocean warming, food depletion, deoxygenation, and acidification. However, over the last decades of intense deep-sea research, no extinction event of a CWC ecosystem is documented, leaving quite some uncertainty on their sensitivity to these environmental parameters. Paleoceanographic reconstructions offer the opportunity to align the on- and offsets of CWC proliferation to environmental parameters. Here, we present the synthesis of 6 case studies from the North Atlantic Ocean and the Mediterranean Sea, revealing that food supply controlled by export production and turbulent hydrodynamics at the seabed exerted the strongest impact on coral vitality during the past 20,000 years, whereas locally low oxygen concentrations in the bottom water can act as an additional relevant stressor. The fate of CWCs in a changing ocean will largely depend on how these oceanographic processes will be modulated. Future ocean deoxygenation may be compensated regionally where the food delivery and food quality are optimal.
... These framework-building organisms sometimes have eastern Spain), in front of Marbella (around the Torrenueva submarine canyon), in front of Málaga and southwest off Almería [6,58,59,64]. Sampling and direct observations of the southern Alboran Sea carbonate mounds (East and West Melilla CWC mound provinces) confirmed that CWCs were the main organism involved in their formation [15,43,46,55]. Nevertheless, some of those CWC mounds are nowadays partly or even completely buried by contouritic and hemipelagic sediments [55,56,65]. ...
... Nevertheless, some of those CWC mounds are nowadays partly or even completely buried by contouritic and hemipelagic sediments [55,56,65]. The distribution and burial state of the observed CWC mounds were explained by changes in water mass dynamics during the Late Quaternary climatic cycles [15,43,46]. ...
... Furthermore, three mound fields have been located within the contouritic terraces of the northern Alboran Sea margin (south-eastern Spain), in front of Marbella (around the Torrenueva submarine canyon), in front of Málaga and southwest off Almería [6,58,59,64]. Sampling and direct observations of the southern Alboran Sea carbonate mounds (East and West Melilla CWC mound provinces) confirmed that CWCs were the main organism involved in their formation [15,43,46,55]. Nevertheless, some of those CWC mounds are nowadays partly or even completely buried by contouritic and hemipelagic sediments [55,56,65]. ...
Carbonate mounds clustering in three fields were characterized on the upper continental slope of the northern Alboran Sea by means of a detailed analysis of the morphosedimentary and structural features using high-resolution bathymetry and parametric profiles. The contemporary and past benthic and demersal species were studied using ROV underwater imagery and some samples. A total of 325 mounds, with heights between 1 and 18 m, and 204 buried mounds were detected between 155 to 401 m water depth. Transparent facies characterize the mounds, which root on at least six erosive surfaces, indicating different growth stages. At present, these mounds are covered with soft sediments and typical bathyal sedimentary habitat-forming species, such as sea-pens, cerianthids and sabellid polychaetes. Nevertheless, remains of colonial scleractinians, rhodoliths and bivalves were detected and their role as potential mound-forming species is discussed. We hypothesized that the formation of these mounds could be related to favorable climatic conditions for cold-water corals, possibly during the late Pleistocene. The occurrence on top of some mounds of abundant rhodoliths suggests that some mounds were in the photic zone during minimum sea level and boreal guest fauna (e.g., Modiolus modiolus), which declined in the western Mediterranean after the Termination 1a of the Last Glacial (Late Pleistocene).
... ; Table 1) and the main basins from the western Mediterranean Sea. Other marine sediment records (circles) used along the text for comparison are: 1) CEUTA10PC08 (914 mbsl; Ausín et al., 2015a); 2) HER-GC-T1 (659 mbsl; Ausín et al., 2015a); 3) GeoB18131-1 (457 mbsl; Wang et al., 2019); 4) MD95-2043MD95- (1841Fletcher et al., 2010;Cacho et al., 1999Cacho et al., , 2006; 5) GeoB 13731-1 (362 mbsl; Fink et al., 2013); 6) MD99-2343 (2391 mbsl; Sierro et al., 2005;Frigola et al., 2007); 7) MD01-2472 (501 mbsl; Toucanne et al., 2012). Yellow line indicates the shelf break. ...
... For the rest of records, although Ca and Ti data have been previously published, the Ti/Ca ratio in this form have not been previously interpreted (see Table 1 for a detailed summary of selected geochemical data used and references to the original papers) (i.e., Jiménez-Espejo et al., 2007Rodrigo-Gámiz et al., 2011). We also used geochemical, grain size data and productivity data, available from the PANGAEA database, for comparison (i.e., Ausín et al., 2020;Frigola et al., 2008;Fink et al., 2013;Wang et al., 2019). ...
... In addition, if the Ti/Ca ratio was mainly controlled by the surface productivity, its variability should be also recorded in other shallow marine cores. Nevertheless, core GeoB13731-1, which is located at 360 m below sea level (mbsl) in the northern Africa margin (Fink et al., 2013;number 5 in Figs. 1, 4f), does not record a Ca decrease during the HS1 and the YD and show a flat pattern during the whole deglaciation. Thus, the Ti/Ca ratio in the studied western Mediterranean records appears to be influenced, but not controlled, by productivity changes at the sub-orbital scale. ...
We present a high-resolution analysis of seven marine sediment records from the western Mediterranean in a transect from the Algero-Balearic basin to the Alboran Sea, spanning the last 20 ka, to decipher the paleoenvironmental and paleoceanographic evolution of the Western Mediterranean Sea. To do so, diverse elemental ratios have been used for reconstructing sediment input variations and paleo-oxygen conditions. In particular, the Ti/Ca ratio has been used to reconstruct variations in the terrigenous and carbonate fractions. However, the specific sedimentary processes controlling this ratio are still poorly understood thus, we also provide new insights for appropriate interpretations, in the studied zone. Our results suggest that the Ti/Ca ratio at the suborbital scale is mostly controlled by bottom current intensity, and less influenced by marine productivity, sea level variations, and the fluvial and eolian inputs. Comparison of diverse records within the western Mediterranean reveals that the Ti/Ca ratio depicted a similar trend in both regions, except during the Heinrich Stadial 1 (HS1) and the Middle Holocene. The HS1 is recorded as a single-phase event in the Algero-Balearic basin, whereas three phases are recognized in the Alboran Sea basin, with a relative minimum in the Ti/Ca ratio. Conversely, during the Middle Holocene, an increase in the Ti/Ca ratio is recorded in the Alboran Sea and the Atlantic Iberian margin, but not in the Algero-Balearic basin, which could be related to the establishment of the Alboran gyres. Redox sensitive proxies, in particular the Mo/Al, U/Al and Mn/Al ratios, point to different phases within the Organic Rich Layer 1 (ORL1): the ORL1a (15-11.7 ka cal BP), characterized by more reducing conditions in the Alboran Sea sediments, and the ORL1b (11.7- ~9 ka cal BP) characterized by suboxic-ferruginous conditions. The sea level transgression, the enhanced fluvial input and the shelf flooding played a key role during the ORL1 onset and demise, increasing the sedimentation rate in the basin and preventing the organic matter oxidation. During the last 2 ka cal BP, an unprecedented common response is recognized in all the studied regions, showing an overall increase in the Ti/Ca ratio, which may be related to intensified human activity in the Mediterranean area, promoting a greater terrigenous input.
... The on-mound core has a recovery of 447 cm and contains coral fragments of various preservation states throughout the core (see Titschack et al., 2016). Previously published coral ages obtained from this core determined by accelerator mass spectrometry (AMS) radiocarbon ( 14 C) dating revealed a pronounced mound formation phase during the Early Holocene (11.2-9.8 kyr BP; Fink et al., 2013). The off-mound core GeoB13731-1 is 431-cm-long and was collected at 360 m water depth about 4 km southeast of the Coral Ridge I from the southward shallowing continental slope (Figure 1; Table 1). ...
... A previously established age model (based on seven AMS 14 C dates of mixed planktonic foraminifer) suggests that the core sediments were deposited during the last ∼23 kyr (for details see Fink et al., 2013). ...
... For this study, all previously published conventional AMS 14 C ages obtained for the on-and off-mound cores (see Fink et al., 2013) were re-calibrated using the software CALIB8.2 (Stuiver et al., 2021 1 ; Table 2A). ...
The formation of cold-water coral (CWC) mounds is commonly seen as being the result of the sustained growth of framework-forming CWCs and the concurrent supply and deposition of terrigenous sediments under energetic hydrodynamic conditions. Yet only a limited number of studies investigated the complex interplay of the various hydrodynamic, sedimentological and biological processes involved in mound formation, which, however, focused on the environmental conditions promoting coral growth. Therefore, we are still lacking an in-depth understanding of the processes allowing the on-mound deposition of hemipelagic sediments, which contribute to two thirds of coral mound deposits. To investigate these processes over geological time and to evaluate their contribution to coral mound formation, we reconstructed changes in sediment transport and deposition by comparing sedimentological parameters (grain-size distribution, sediment composition, accumulation rates) of two sediment cores collected from a Mediterranean coral mound and the adjacent seafloor (off-mound). Our results showed that under a turbulent hydrodynamic regime promoting coral growth during the Early Holocene, the deposition of fine siliciclastic sediments shifted from the open seafloor to the coral mounds. This led to a high average mound aggradation rate of >130 cm kyr–1, while sedimentation rates in the adjacent off-mound area at the same time did not exceed 10 cm kyr–1. Thereby, the baffling of suspended sediments by the coral framework and their deposition within the ecological accommodation space provided by the corals seem to be key processes for mound formation. Although, it is commonly accepted that these processes play important roles in various sedimentary environments, our study provided for the first time, core-based empirical data proving the efficiency of these processes in coral mound environment. In addition, our approach to compare the grain-size distribution of the siliciclastic sediments deposited concurrently on a coral mound and on the adjacent seafloor allowed us to investigate the integrated influence of coral mound morphology and coral framework on the mound formation process. Based on these results, this study provides the first conceptual model for coral mound formation by applying sequence stratigraphic concepts, which highlights the interplay of the coral-framework baffling capacity, coral-derived ecological accommodation space and sediment supply.
... Darwin and Moira Mounds; Bett et al., 2001;Foubert et al., 2011) to giant ridge-like mounds that rise hundreds of meters above the surrounding seafloor (e.g. Challenger Mound and Brittlestar mounds; Kano et al., 2007;Comas and Pinheiro, 2010;Fink et al., 2013). Laterally, coral mounds can expand hundreds of meters for sub-circular shapes and extend for several kilometres in ridge-like morphologies (Huvenne et al., 2005;Mienis et al., 2006;Lo Iacono et al., 2018a). ...
... Therefore, further mapping expeditions along the continental margins of the Atlantic Ocean and the Mediterranean Sea would most probably result in the discovery of new CWC coral mound provinces. (Lopes and Hajdu, 2014); 3, Southern Caribbean Coral Reefs/Mounds (Reyes et al., 2005); 4, Campeche Mounds ; 5, Gulf of Mexico Mounds (Georgian et al., 2016); 6, Viosca Knoll Mounds (Brooke and Schroeder, 2007); 7, West Florida Mounds (Neumann et al., 1977); 8, Florida Mounds (Grasmueck et al., 2006); 9, Cape Lookout Mounds ; 10, Namibia Mounds 11, Angola Mini Mounds (Le Guillox et al., 2009);12, Ghana Mounds (Buhl-Mortensen et al., 2017); 13, Banda Mounds (Eisele et al., 2014); 14, Eugen Seibold Mounds (Glogowski et al., 2015); 15, Pen Duick Mounds (Van Roij et al., 2011);16, West Melilla Mounds (Lo Iacono et al. 2014); 17, East Melilla Mounds (Fink et al., 2013);18, Cabliers Mound (Lo Iacono et al. 2016);19, Chella Mound (Lo Iacono et al., 2018); 20, Tuscan Archipelago Mounds Angeletti et al., 2020); 21, Pantelleria Mounds (Martorelli et al., 2011); 22, Santa Maria di Leuca Mounds ; 23, Breoghan Mounds (Somoza et al., 2014);24, Ferrol and Coruña Canyon Mini Mounds (Lo Iacono et al., 2018);25, Penmarc'h and Guilvinec mini Mounds (De Mol et al., 2011); 26, Explorer and Dangeard mini Mounds (Stewart et al., 2014); 27, Arc Mounds (Mohn et al., 2014); 28, Porcupine Bank Canyon Mounds (Mazzini et al., 2012); 29, Hovland Mounds (Hovland et al., 1994); 30 Magellan Mounds (Hovland et al., 1994); 31, Viking Mounds (Foubert et al., 2011); 32, Galway Mounds ; 33, Therese Mounds (De Mol et al., 2007); 34, Challenger Mound (Kano et al., 2007); 35, Macnas Mounds (Wilson et al., 2007); 36, Enya Mounds ; 37, Pelagia Mounds (Kenyon et al., 2003); 38, Logachev Mounds (Kenyon et al., 2003); 39, Francken Mounds (Wienberg et al., 2008); 40, Mingulay Mounds ; 41, Darwin Mounds (Masson et al., 2003); 42, Tisler Reef (Wild et al., 2009);43, Sula Reef (Freiwald et al., 2002); 44, Traena Reef/Mounds (Lindberg, 2004); 45, Røst Reef (Freiwald et al., 2004); 46, Stjernsund Reef/Mounds (Freiwald et al., 1997). ...
... Although there is not a global pattern for coral mound development, it generally follows glacial-interglacial cycles as main climatic driver, with mound formation occurring either in interglacial (e.g. Irish, Scottish and Norwegian mounds; Kano et al., 2007;de Haas et al., 2009;Thierens et al., 2010;Frank et al., 2011), glacial (Gulf of Cadiz, Mauritanian and Argentinian mounds; Wienberg et al., 2010;Eisele et al., 2011;Steinmann et al., 2020) or deglacials and temperate interstadial periods (Mediterranean mounds: Fink et al., 2013;Wang et al., 2019), depending on the environmental setting of their location. Atlantic coral mounds north of 50° N display a prominent mound aggradation during the Holocene and prior interglacial periods Frank et al., 2011;Kano et al., 2007). ...
Scleractinian cold-water coral reefs are considered to be key hotspots of benthic biodiversity in the deep ocean. Due to their relevant ecological role and susceptibility to anthropogenic disturbances protection and conservation measures have been applied to these habitats, even though they are far from being completely understood. Throughout the last two decades several studies have quantitatively described the biodiversity of Atlantic cold-water coral reefs, finding considerable differences among biogeographic regions. In contrast, and probably owed to the scarcity of these habitats in the Mediterranean Sea, the knowledge related to coral reef biodiversity in this basin remains modest and almost purely qualitative. On a different note, when coral reefs are under persistent suitable environmental conditions and have a sufficient sediment input, they can develop and form large geomorphic structures known as coral mounds. The latter are sensitive to changes in climate and capable of recording such variations in the chemical composition of the coral skeletons. Numerous surveys in the Atlantic have associated coral mound development patterns to environmental variations caused by glacial-interglacial cycles. Within the Mediterranean, coral mound formation studies have been so far limited to the Alboran Sea and to the last 15 kyr, due to the lack of gravity cores encompassing longer periods of time. In this thesis a wide range of techniques, including ROV video-analysis, multivariate statistics, U-series dating, computed tomography and geochemical analyses were applied to acquire a better understanding of the spatiotemporal distribution of Mediterranean cold-water coral reefs and the processes controlling their evolution into mounds during the last 400 kyr. More precisely, the present study aimed to (1) quantify the density of uncommonly thriving coral reefs and accompanying megabenthic species within the Cabliers Coral Mound Province, and describe their distribution along it; and (2) explore which are the main environmental variables and paleoclimatic events that have controlled coral mound formation in Cabliers and in the newly discovered Tunisian Coral Mound Province. The research presented here revealed the densest and most flourishing cold-water coral reefs witnessed so far in the Mediterranean Sea and brought further insight into their distribution along the crests of ridge-like coral mounds. This thesis also contributed to increase our knowledge on the main species associated to Mediterranean coral reefs and their relative abundances, which showed considerable differences to those found in Atlantic reefs. In regards to coral mound formation, this work has expanded the current knowledge outside the Alboran Sea and back to 400 ka BP. Almost opposite development patterns were observed between the Cabliers and Tunisian coral mound provinces, with the former mainly developing throughout deglaciations and temperate interstadial periods and the latter during glacial periods. Nonetheless, both provinces seem to depend on a high surface productivity and an appropriate depth of the interface between Atlantic and Levantine Intermediate Waters for the coral mounds to develop. Lastly, the oceanographic alterations caused in the Eastern Mediterranean Basin during Sapropel events also seem to have had detrimental effects for coral mound formation in the Western basin.
... This chapter will not address recent studies on the proliferation and demise of Mediterranean CWC in the past linked to specific environmental conditions, such as changes in seawater temperature, oxygen content, carbonate chemistry, nutrient content or sedimentation regime (Malinverno et al. 2010;Margreth et al. 2011;McCulloch et al. 2010;Taviani et al. 2011;Fink et al. 2012Fink et al. , 2013Fink et al. , 2015, as these long-term coral population dynamics based on geochronological data are discussed in other chapters of the book (see Vertino et al., ...
... In particular, COCs show systematically lower δ 18 O, δ 13 C, δ 11 B and U/Ca values and higher Mg/Ca, Li/Ca, P/Ca and Ba/Ca ratios compared to the fibrous aragonite (Montagna et al. , 2008a(Montagna et al. , 2014Blamart et al. 2007;Rollion-Bard and Blamart 2014). It is clear that sub-sampling different coral portions having distinctive proportions of COCs vs. FA leads to different geochemical results and eventually contrasting paleoclimate Taviani et al. 2011Taviani et al. , 2016Fink et al. 2012Fink et al. , 2013Fink et al. , 2015Montagna et al. 2014;Angeletti et al. 2015;Del Bianco et al. 2015;Dubois-Dauphin et al. 2016Titschack et al. 2016) reconstructions. Several approaches have been developed to correct for this biological overprint (e.g. ...
... A very recent study investigated Nd isotopes in Mediterranean CWC spanning the last ~13 kyrs (Dubois-Dauphin et al. 2017). Coral fragments were collected in the Sardinia Channel at 414 m water depth (Taviani et al. 2017) and in the Alborán Sea between 280 and 442 m water depth (Fink et al. 2013) and analysed for Nd isotopes. Results reveal relatively constant εNd values through time for both locations, with the sole notable exception being a large shift at ~ 8.7 kyrs BP toward non-radiogenic εNd values in the Sardinian record (from −7.55 ± 0.2 at 10.170 kyrs BP to −8.66 ± 0.3 at 8.703 kyrs BP), indicative of a strong reduction of the LIW formation in the eastern Mediterranean basin during the sapropel S1 event (Dubois-Dauphin et al. 2017). ...
... The CWC-factory is a sedimentary system that has the ability to construct several tens to hundreds of metres high sedimentary structures at varying water depths below the storm-wave base. These systems consist of a living coral framework producing coarse rubble, together with a large variety of other biota, but also act as a sediment baffler enabling fast mound/ridge accumulation ( Fig. 11; Dorschel et al., 2007;Huvenne et al., 2009;Fink et al., 2013). While framebuilding corals forming mounds predominate in this system, the sediment production term 'Frame' is proposed for this factory . ...
... These sedimentary systems may form large-scale clusters of mounds with various shapes and heights ( Fig. 11; e.g. Mienis et al., 2007;Fink et al., 2013;Hebbeln et al., 2019). Vertical mound accretion rates of 220 cm/kyr were reported from the giant coral mounds off Ireland ). ...
... The sedimentary successions of cold-water coral systems usually display a succession of coral fragments embedded in a matrix of hemipelagic sediments alternating with intervals with reduced sedimentation or erosion (Fink et al., 2013). Mounds at the south-west Rockall Trough (Fig. 11F) consist of a Holocene coral-dominated interval overlying lithified intervals lacking coral fragments containing coccoliths covered by calcite cements (van der Land et al., 2010(van der Land et al., , 2014. ...
The carbonate factories model, as defined at the beginning of the century, provides a subdivision of marine carbonate sediment production-systems based on the style of carbonate precipitation. The main factors controlling marine carbonate precipitation are light, water temperature, nutrients, salinity, substrate and carbonate saturation. Site-specific controls influencing the systems comprise ocean currents, upwelling and non-upwelling systems, ocean-atmosphere systems, atmospheric systems, shallow-water dynamics, and terrestrial sediment and water input.
Each factory has its own sediment-production window linking optimal sediment production with selected environmental controls. Sediment production in the tropical factory (T-factory) is light and temperature dependent and negatively impacted by nutrients. Sediment production and export depends on the size of the shallow-water areas within the photic zone. The cold-water-coral factory (CWC-factory) is nutrient dependent, but light independent. Sediment production relates to nutrient supply enabling the growth of the cold-water corals. The cool-water factory (C-factory) displays a strong link to nutrients and water temperature, with parts that are light-dependent, for example, sediment production in kelp dominated environments. The sediment mineralogy and sediment production area within the high-energy hydrodynamic zone govern sediment distribution with sediment behaviour comparable to siliciclastics. The Microbial/Mud-Mound factory (M-factory) is nutrient dependent and to some extent temperature and light independent. Sediment production and export is referred to here as slope shedding and links to the main sediment production on the upper slope. The planktic factory (P-factory) depends on variations in light, temperature and nutrients resulting in fluctuating pelagic fall-out.
Platform morphologies and slope profiles are also factory specific: T-factories show a rimmed flat-topped platform with adjacent exponential slopes or a carbonate ramp morphology; CWC-factories display mound morphologies with steep slopes; C-factories are associated with open shelf systems and Gaussian shaped slope profiles; while M-factories are characterized by individual steep-sided mounds or flat-topped platforms with deepened margins and a linear shaped slope profile. The P-factory provides biotic grains to all environments and at times, like for the Cretaceous, may dominate sedimentation patterns in the basin realm.
The sequence stratigraphic patterns substantially differ between factories. The T-factory being light-dependent is characterized by higher sediment production when the platform tops are flooded (highstand shedding). It displays decoupled sediment wedges with the partial infill of accommodation in the shallow-water realm and major sediment export towards the slopes and surrounding basins. The CWC-factory is marked by in situ production and deposition with limited sediment export forming single CWC spots or sediment accumulation ridges. The C-factory has a siliciclastic equivalent style of sediment distribution with lowstand-dominated, shelf edge wedges and a shaved-off shelf during sea-level highstands. Slope shedding marks the M-factory in which sediment production occurs within the upper slope realm of the flat-topped platforms both during highstands and lowstands in sea-level. This allows for fairly continuous sediment production exhibiting minor impact of sea-level changes, but with progradation, aggradation and retrogradation of the system being only limited by local environmental changes. P-factory sediment production may vary in accordance with variations in sea-level, providing time-lines and systems tracts boundaries in the pelagic realm.
In summary, each factory is branded by an individual set of features, for example, production window, sediment production and export, morphologies and slopes. It is this unique set of variables marking each factory that determines the factory-dependent response to small-scale and large-scale environmental changes through space and time as shown in the sequence stratigraphic development.
... Darwin and Moira Mounds; Bett et al., 2001;Foubert et al., 2011) to giant ridge-like mounds that rise hundreds of meters above the surrounding seafloor (e.g. Challenger Mound and Brittlestar mounds; Kano et al., 2007;Comas and Pinheiro, 2010;Fink et al., 2013). Such mound morphologies are sometimes associated with the presence of a geological structure on which the corals first settled and started to grow (Lo Iacono et al., 2014Hebbeln, 2019). ...
... Li, Mg, U, Ba, B, Nd) that reflect the local physicochemical parameters of the surrounding water (Montagna et al., 2014;Spooner et al., 2018). As paleoclimatic archives, absolutely dated CWCs combined with the extraction of geochemical proxies and computed tomography scans can thus give highly relevant information on coral mound development and its paleoclimatic constrains (Fink et al., 2013;Raddatz et al., 2016;Montagna and Taviani, 2019;Wang et al., 2019). ...
... In the Mediterranean basin, CWC mound provinces tend to occur together with contourite deposits (Rebesco and Taviani, 2019) and are concentrated in the Ionian Sea (Savini and Corselli, 2010;Savini et al., 2014), the Thyrrhenian Sea (Remia and Taviani, 2005;Angeletti et al., 2020) and the Alboran Sea, this last being the only basin where mounds reach sizes of >100 m in height and several kilometres in length (Comas and Pinhero, 2010;Fink et al., 2013;Lo Iacono et al., 2014Corbera et al., 2019). Several studies have attempted to link coral mound growth patterns in the Alboran Sea to different environmental factors, in order to better understand what are the main processes driving or limiting CWC mound development in the region (Fink et al., 2013(Fink et al., , 2015Lo Iacono et al., 2014;Stalder et al., 2015;Wang et al., 2019). ...
Cold-water coral mounds are key hot-spots of deep ocean biodiversity and also important archives of past climatic conditions. Nonetheless, the paleo-oceanographic setting in which coral mounds developed in the Mediterranean Sea during the last 500 ka still needs to be properly understood. This study describes the coral deposits and corresponding ages of two on-mound gravity cores acquired from opposite sectors of the newly discovered Cabliers Coral Mound Province (CMP, Alboran Sea, W Mediterranean). U eTh data revealed Pleistocene-aged corals covering mound formation periods from >389 to 9.3 ka BP and from 13.7 to 0.3 ka BP in the southern and northern mounds respectively. The coral-rich deposits of the cores were mainly dominated by Desmophyllum pertusum, although in some sections concurrent with the Middle Pleistocene and the Holocene, other corals such as Dendrophyllia cornigera and Madrepora oculata also appeared as dominating species. Coral mound formation stages generally occurred during deglacials and temperate interstadial (3.5e4.1 d 18 O‰) periods, whereas during interglacials (<3.5 d 18 O‰) coral mound formation only occurred in the northern and shallower mound. We interpret this to indicate that the shoaling of the interface between Atlantic (AW) and Levantine Intermediate Waters (LIW) during interglacial periods prevented the corals in the southern CMP from acquiring sufficient food supply, thus causing periods of coral mound stagnation. Similarly, the interruption in LIW formation throughout sapropel events also coincides with coral mound stagnation phases. This suggests that sapropel-derived processes, which originated in the eastern Mediterranean, likely affected the entire Mediterranean basin and further supports the role of LIW as a conveyor belt facilitating cold-water coral growth in the Mediterranean Sea. Overall, we show that these coral mounds yield important insights into how local changes in oceanographic conditions can influence coral mound development.
... Living scleractinian CWCs, mostly represented by M. oculata, are presently found in the Mediterranean Sea. They have, for example, been observed in the Northern Ionian Sea (Savini et al., 2014), in the Sicily channel , in the Tyrrhenian Sea (Taviani et al., 2017(Taviani et al., , 2019, in the Adriatic and Aegean Seas (Vafidis et al., 1997;Freiwald et al., 2009), in the Gulf of Lions (Zibrowius, 2003;Orejas et al., 2007;Fabri et al., 2014), and at the summit of ridges in the Alboran Sea Fink et al., 2013;Lo Iacono et al., 2014;Stalder et al., 2015Stalder et al., , 2018Wang et al., 2019). The oldest occurrences of fossil CWC mounds in the Mediterranean Sea date back to the Late Pliocene/Early Pleistocene and are related to the recolonization of the Mediterranean Sea by CWCs after the Messinian Salinity crisis (Taviani et al., 2005;Vertino et al., 2014). ...
... The summits of these Brittlestar Ridges are at ca. 250 m depth, whilst their base is found at ca. 450 m depth Lo Iacono et al., 2014;Wang et al., 2019;Figure 1). They are between 100 and 250 m wide and extend up to 3 km in length Fink et al., 2013). ...
... The recent (last 20 ka) history of coral proliferation of the East Melilla Coral Province has been documented by a number of studies in the past years (Fink et al., 2013(Fink et al., , 2015Stalder et al., 2015Stalder et al., , 2018Wang et al., 2019;Feenstra, 2020). The conclusions drawn from these different studies indicate that corals experienced their most intense recent proliferation phase during Greenland Interstadial 1 (GI-1) and during the Early Holocene, whilst coral growth was reduced or halted during the Mid to Late Holocene, Younger Dryas and Last Glacial Maximum. ...
The Alboran Sea is widely recognized to host numerous cold-water coral ecosystems, including the East Melilla Coral Province. Yet, their development through time and response to climatic variability has still to be fully understood. Based on a combined investigation of benthic foraminiferal assemblages, foraminiferal stable isotope compositions, grain size analysis, sediment geochemistry, and macrofaunal quantification, this study identifies key events and processes having governed cold-water coral development at the East Melilla Coral Province between Greenland Stadial 2.1 and the Early Holocene. The transition from Greenland Stadial 2.1 to Greenland Interstadial 1 is associated to a decline of bryozoan communities and their replacement by cold-water corals, together with changes in benthic foraminiferal assemblages and a decrease in the sediment mean grain size. These results suggest that a rapid decrease in bottom currents and the establishment of dysoxic and mesotrophic conditions at the seafloor, possibly associated to enhanced fluvial input, resulted in the decline of bryozoans as the dominant suspension feeding organisms and their replacement by a thriving cold-water coral community. This transition from a bryozoan to a coral dominated environment is concomitant with the beginning of the African Humid Period, confirming that increasing fluvial input could have been a main factor triggering the establishment of cold-water corals in the East Melilla Coral Province during Greenland Interstadial 1. A change in benthic foraminiferal communities and an increase in the sediment mean grain size mark the passage from the Early to Late Greenland Interstadial 1. The current velocity of intermediate water masses is suggested to have increased during the Early to Late Greenland Interstadial 1, whilst simultaneously fluvial input would have reduced. Such changes suggest that the climate became more arid during the second phase of Greenland Interstadial 1.
... The Beta carbonate mound on the Moroccan North Atlantic margin was investigated for sedimentology and stable isotope (oxygen and carbon) by De Mol et al. (2011Mol et al. ( , 2012, Terhzaz (2019), Fink et al. (2013), Titschack et al. (2016) and Terhzaz et al. (2018) studied the sedimentology and geochemistry of the sediments recovered on the Brittlestar I ridge and Cabliers Mound along the Moroccan Mediterranean margin. Benthic foraminiferal and ostracod assemblages were related to the circulation patterns and marine productivity in the Alboran Sea (Fink et al., 2013;Stalder et al., 2015Stalder et al., , 2018Stalder et al., , 2019. ...
... The Beta carbonate mound on the Moroccan North Atlantic margin was investigated for sedimentology and stable isotope (oxygen and carbon) by De Mol et al. (2011Mol et al. ( , 2012, Terhzaz (2019), Fink et al. (2013), Titschack et al. (2016) and Terhzaz et al. (2018) studied the sedimentology and geochemistry of the sediments recovered on the Brittlestar I ridge and Cabliers Mound along the Moroccan Mediterranean margin. Benthic foraminiferal and ostracod assemblages were related to the circulation patterns and marine productivity in the Alboran Sea (Fink et al., 2013;Stalder et al., 2015Stalder et al., , 2018Stalder et al., , 2019. Age constrain for corals, benthic foraminifera and associated fauna through time was proved by Aguilar et al. (2013), Fink et al. (2013) and Stalder et al. (2015Stalder et al. ( , 2018Stalder et al. ( , 2019. ...
... Benthic foraminiferal and ostracod assemblages were related to the circulation patterns and marine productivity in the Alboran Sea (Fink et al., 2013;Stalder et al., 2015Stalder et al., , 2018Stalder et al., , 2019. Age constrain for corals, benthic foraminifera and associated fauna through time was proved by Aguilar et al. (2013), Fink et al. (2013) and Stalder et al. (2015Stalder et al. ( , 2018Stalder et al. ( , 2019. ...
A palynological study of carbonate mounds of Atlantic and Mediterranean Moroccan margins was conducted on sediment boxcores MD13-3441, MD13-3456, MD13-3461, MD13-3465, MD13-3468 collected during the oceanographic cruise MD 194/Eurofleet - GATEWAY, which took place on June 2013.
The organic remaining revealed a dominance of dinoflagellate cysts over the continental fraction, which showed very low rates. The use of pollen data, despite their low representativity, is proving to be a valuable tool for the paleoclimate interpretation.
The palynological quantitative and qualitative analysis revealed the evolution of the paleoenvironment and climate change of the carbonate mounds during this study interval. The terminal Pleistocene–basal Holocene passage highlighted by the dominance of cold taxa of dinoflagellate cysts. The presence and dominance of tree and shrub pollen coupled by the presence of altitudinal conifers confirmed a cold climate in both continental and marine environments.
During the lower-middle Holocene, the variations in the relative frequencies of dinoflagellate cyst associations reflect the evolution of the paleoenvironment from inner neritic to oceanic.
The recorded microflora shows a cyclicity during the lower Holocene from arid to semi-arid between 10.07 and 9.85 ka (the abundance of herbaceous and steppe), to become arid again around (9.69 ka) by the consistently high rate of herbaceous and steppe.
In contrast, the paleoclimate recorded during the Middle Holocene is semi-humid to 6.29 ka (high rate of trees and shrubs) and evolves to a warm dry climate at 5.9–5.14 ka, reflected by the abundance of herbaceous and steppe.
... Mound aggradation in the EMCP is controlled by different environmental factors, such as surface and export productivity, bottom water hydrodynamics and oxygen content in the water. These conditions seem to be steered by the water column structure in the study area (Fink et al., 2013;Stalder et al., 2015;. In contrast, still little is known about past coral growth and mound formation in the WMCP. ...
... It most likely reflects different hydrodynamic regimes during mound formation (Hebbeln, 2019). Nevertheless, the knowledge about mound formation in this area is limited to the northern and westernmost sub-clusters of the EMCP (Fink et al., 2013;Stalder et al., 2015;. Nothing is known so far about mound formation in the central and southern sub-clusters of the EMCP. ...
... To answer these questions, three studies were designed and conducted as reported in the following chapters. In the first study, two sediment cores (on-and off-mound cores) from the EMCP that already provided a record on mound development since the last deglaciation were used (Fink et al., 2013). In this project, each core is used to reconstruct changes of the hydrodynamic conditions and associated sedimentary process during mound formation for the respective setting. ...
Cold-water coral (CWC) mounds are formed due to the sustained growth of CWCs over geological timescales (thousands to tens of thousands of years). These seabed structures are discovered along continental margins of the Atlantic Ocean and its marginal seas. They are important archives for reconstructing the long-term development of CWCs and coral mounds. However, our knowledge about the coral mound formation and associated sedimentary processes is still limited. In the Mediterranean Sea, most CWC mounds were discovered in the so-called West and East Melilla CWC mound province (WMCP and EMCP, respectively). Particularly, coral mounds in the EMCP are arranged into four sub-clusters, each marked by specific morphologies and dimensions. The coral mound formation in the northern and westernmost sub-clusters of the EMCP has been reconstructed, whereas little is known about the history of coral mounds formation in the other unexplored sub-clusters of the EMCP, as well as the entire WMCP. Therefore, this thesis focuses on the CWC mound development in the southern Alboran Sea and the dominant environmental factors favoring the coral mound formation.
... This chapter will not address recent studies on the proliferation and demise of Mediterranean CWC in the past linked to specific environmental conditions, such as changes in seawater temperature, oxygen content, carbonate chemistry, nutrient content or sedimentation regime (Malinverno et al. 2010;Margreth et al. 2011;McCulloch et al. 2010;Taviani et al. 2011;Fink et al. 2012Fink et al. , 2013Fink et al. , 2015, as these long-term coral population dynamics based on geochronological data are discussed in other chapters of the book (see Vertino et al., ...
... In particular, COCs show systematically lower δ 18 O, δ 13 C, δ 11 B and U/Ca values and higher Mg/Ca, Li/Ca, P/Ca and Ba/Ca ratios compared to the fibrous aragonite (Montagna et al. , 2008a(Montagna et al. , 2014Blamart et al. 2007;Rollion-Bard and Blamart 2014). It is clear that sub-sampling different coral portions having distinctive proportions of COCs vs. FA leads to different geochemical results and eventually contrasting paleoclimate Taviani et al. 2011Taviani et al. , 2016Fink et al. 2012Fink et al. , 2013Fink et al. , 2015Montagna et al. 2014;Angeletti et al. 2015;Del Bianco et al. 2015;Dubois-Dauphin et al. 2016Titschack et al. 2016) reconstructions. Several approaches have been developed to correct for this biological overprint (e.g. ...
... A very recent study investigated Nd isotopes in Mediterranean CWC spanning the last ~13 kyrs (Dubois-Dauphin et al. 2017). Coral fragments were collected in the Sardinia Channel at 414 m water depth (Taviani et al. 2017) and in the Alborán Sea between 280 and 442 m water depth (Fink et al. 2013) and analysed for Nd isotopes. Results reveal relatively constant εNd values through time for both locations, with the sole notable exception being a large shift at ~ 8.7 kyrs BP toward non-radiogenic εNd values in the Sardinian record (from −7.55 ± 0.2 at 10.170 kyrs BP to −8.66 ± 0.3 at 8.703 kyrs BP), indicative of a strong reduction of the LIW formation in the eastern Mediterranean basin during the sapropel S1 event (Dubois-Dauphin et al. 2017). ...
Scleractinian cold-water corals preserve in their aragonite skeleton information on the past changes of the physico-chemical properties of the seawater in which they grew. Such information is stored as geochemical signals, such as changes in trace elements concentration (B/Ca, Li/Mg, P/Ca, Sr/Ca, Ba/Ca, U/Ca) or stable and radiogenic isotopes composition (δ¹¹B, δ¹³C, δ¹⁸O, ¹⁴C, εNd), that are usually converted into environmental parameters using empirical calibration equations. The aragonite skeleton of cold-water corals is sufficiently uranium-rich to be suitable for U-series dating, providing precise and accurate ages for the last 600–700 kyrs. This opens the possibility to obtain reconstructions of key oceanographic parameters for the intermediate and deep water masses at sub-decadal scale resolution for climatically-relevant time windows in the past. However, part of the geochemical signal incorporated into the coral skeleton is modulated by the physiology of the coral, which complicates the interpretation of the geochemical proxies. This “vital effect” needs to be taken into account and corrected for to obtain reliable reconstructions of past changes in seawater temperature, pH and nutrient content. On the other hand, these biologically-induced geochemical signals can be used to investigate the processes controlling coral biomineralisation and better understand the resilience of cold-water corals to environmental and climate changes.
... The only other information about Middle Pleistocene CWC known hitherto in the Mediterranean derives from research in progress on submerged coral mounds of the Alborán Sea, drilled using the Bremen Seafloor Drill Rig (MeBo) (Hebbeln et al. 2015;Krengel et al. 2017;Wienberg, this volume). In this area large seabed structures made up by CWC occur from 230 to 450 m water depth (Fink et al. 2013(Fink et al. , 2015Lo Iacono et al. 2014a, b;Stalder et al. 2015;Wienberg and Titschack 2017; Wienberg, this volume). ...
... The Alborán Sea represents the most spectacular CWC mound region known so far in the Mediterranean Sea, both for the wide extension of the mounds (Fink et al. 2013(Fink et al. , 2015Lo Iacono et al. 2014a, b;Wienberg, this volume) and for the diversified fossil and modern fauna associated to frame-building coral communities (Lo Iacono et al. 2014bStalder et al. 2015;Lo Iacono et al. 2016;Wienberg, this volume). The largest coral mounds of the Eastern Melilla Coral Province seem to be dated back to the Middle Pleistocene (Krengel et al. 2017), but data collected so far from superficial deposits indicate that frame-building CWC (at least L. pertusa) were common between ~13.5 and 12.5 and ~11.5 and 10.5 kyr BP ( Fig. 9.5a; Appendices 9.2 and 9.3), with an apparent decline phase between ~12.2 and ~11.6 kyr BP (Wienberg, this volume). ...
... By combining all ages (last 50 kyr) of M. oculata and L. pertusa published thus far (Fig. 9.4), it is evident the highly frequent occurrence of L. pertusa during the late Bølling-Allerød, the early Younger Dryas and in the Early Holocene. The distribution and number of coral ages (Fig. 9.4), confirmed by observations carried out on sediment cores from both eastern and western Mediterranean coral mounds (Malinverno et al. 2010;Stalder et al. 2015;Fink et al. 2012Fink et al. , 2013Fink et al. , 2015, indicate "switches" in the dominance of the most common frame-building coral species (L. pertusa vs M. oculata). ...
Cold-water corals have inhabited the Mediterranean basin since at least the Miocene, undergoing important modifications through time. Most information regarding pre-Pleistocene occurrences of extant cold-water coral species still relies on ancient literature records in need to be updated according to modern taxonomic and chronostratigraphic concepts. In this chapter, Neogene and Quaternary coral records are discussed. Many occurrences have been revised from the taxonomic point of view through the analysis of historical museum collections, newly collected specimens and original species descriptions and illustrations. In particular, this study summarises the current state of knowledge on Mediterranean frame-building cold-water corals and associated solitary species from the Miocene onwards. Several growth and demise phases, as well as changes in composition of dominant species have been observed so far. A shift from Dendrophyllia- to “Atlantic-like” Lophelia-dominated paleocommunities occurred at the Pliocene – Pleistocene boundary. “Golden ages” for the species Lophelia pertusa, and large bioconstructions formed by this coral, are thus far known in the Early Pleistocene (Calabrian stage), at the boundary Bølling- Allerød – Younger Dryas and in the Early Holocene (at least in the western basin). A large knowledge gap currently exists between the end of the Calabrian stage and the last 50 kyr BP. Several Atlantic deep-sea species (including frame-building and “psychrosperic” cold-water corals), common in the Early Pleistocene, disappeared in the Mediterranean after the Late Pleistocene, but how and when this event occurred is not known yet. Further studies need to be carried out to understand if there is any correlation between this deep-sea basin-scale extinction and the decline of Lophelia-dominated bioconstructions observed in the late Younger-Dryas and after the Early Holocene. In order to fill knowledge gaps on the fossil record of Mediterranean cold-water corals and to fully exploit the valuable potential of these organisms as palaeoenvironmental archives, the setup of a comprehensive open access database, including quality-controlled data on both modern and fossil species, is highly recommended. This would also provide a useful tool for managing, valorising and preserving the unique, yet undervalued paleontological heritage of the Mediterranean regions.
... In the north, steep and elongated ridges (Brittlestar ridges I to III) are attached to the southern edge of the Provençaux bank ( Fig. 7.1a). They have heights of 50-150 m and rise to water depths of 250-450 m (Fink et al. 2013). Their morphology and orientation might point to a tectonic-related origin, but a recent drilling campaign revealed that at least the upper 70 m of these ridges are made up of coral-sediment-deposits (Hebbeln et al. 2015). ...
... Until the present day, ~80 datings have been published for both species (Fig. 7.1b). This dataset contains datings obtained from CWC fragments collected from the seabed surface (n = 35), which mainly originate from seamounts (see compilation by Fink et al. 2015 and references therein), while the majority of ages (n = 47) derive from core records retrieved from coral mounds along the Moroccan margin (Fink et al. 2013;Stalder et al. 2015;Dubois-Dauphin et al. 2016;unpubl. Data Wienberg). ...
... Yet, preliminary dating results obtained from 70-m-long drill cores collected from the East Melilla province (Hebbeln et al. 2015) revealed that there was indeed no sustained occurrence of L. pertusa and M. oculata lasting since ~100,000 years BP until the last deglaciation, thus a time span covering the last glacial, and part of the preceding interglacial (Krengel et al. 2015). There is a conspicuous common start-up phase for their occurrence coinciding with the onset of the Bølling-Allerød (BA) warm interval at ~14,600 years BP (Fig. 7.1b), which marked the onset of the last deglaciation with a post-glacially rising sea level (Fink et al. 2013;Stalder et al. 2015;Lo Iacono et al. 2016;see Vertino et al., this volume and references therein). The rst post-glacial period of pronounced coral occurrence lasted until the mid-Younger Dryas (~12,200 years BP) and is followed by a second boost roughly covering the entire Early Holocene (11,600-8,300 years BP; Fig. 7.1b). ...
The two scleractinian cold-water corals Lophelia pertusa and Madrepora oculata are widely distributed in the Alborán Sea. They have been found (alive and fossil) on seamounts, volcanic ridges and mud volcanoes, and they formed coral mounds in the geological past. While the cold-water corals show a reduced occurrence during the last glacial period, they experienced a boom since the last deglaciation until the Early Holocene. The proliferation of cold-water corals during this time is expressed in very high vertical mound aggradation rates of >400 cm kyr⁻¹. Since the mid-Holocene coral mound aggradation significantly slowed-down, which is ascribed to the reduced occurrence of cold-water corals likely supplemented by a reduced sediment supply. During the Holocene, a shift in coral species dominance towards a M. oculata-dominated cold-water coral community becomes apparent. It is speculated that in comparison to L. pertusa, M. oculata has a higher tolerance against the increasing Holocene bottom water temperatures, but is not efficient in building-up mounds likely attributed to its thinly branching framework.
... mounds and reefs) have received growing attention over the last 30 years (Freiwald et al., 1997;Hovland et al., 1994). They have now been reported as relatively common across the world's seas and oceans, although essentially documented in the Atlantic Ocean and Mediterranean Sea (Carranza et al., 2012;Fink et al., 2013;Matos et al., 2015;Mienis et al., 2014;Raddatz et al., 2020;Ramos, et al., 2017;Reolid et al., 2017;Steinmann et al., 2020;Tamborrino et al., 2019;Tracey et al., 2011;Wheeler et al., 2007;Wienberg et al., 2018), and as regionally important contributors to the calcium carbonate budget (Dorschel et al., 2005a;Lindberg & Mienert, 2005;Titschack et al., 2009Titschack et al., , 2016. The main frameworkforming scleractinian corals in the North Atlantic realm (i.e. ...
... This challenges the applicability of the sortable silt mean grain size as a palaeocurrent proxy in CWC mounds. Past studies have therefore used grain size and sortable silt to evaluate past bottom current velocities in the surrounding off-mound contourites (Fink et al., 2013;Matos et al., 2015;Wang et al., 2019). However, this only documents past current dynamics in off-mound areas and does not necessarily reflect or even record those governing the coral mound itself and the coral communities it hosts. ...
Surface benthic foraminiferal assemblages associated with cold‐water coral mounds and reefs from the Irish margin and Norwegian shelf (North‐east Atlantic) are for the first time compared quantitatively. Results indicate that the considered sites share a common assemblage, dominated by elevated epibenthic and distinct infaunal species. This surface assemblage is typical of environments that are subject to strong bottom‐water turbulence with enhanced food availability. It provides a benchmark for comparison with fossil benthic foraminiferal assemblages from past cold‐water coral environments. Similar to macrofaunal and megafaunal communities, surface benthic foraminiferal diversity is higher on reefs and mounds than in surrounding off‐mound/off‐reef sediments. Benthic foraminiferal diversity is highest within the living coral macrohabitat, possibly as a result of enhanced availability and variety of food sources, and ecological niche separation. Indeed, living coral generally thrives on the summits or flanks of reefs and mounds where food availability is most important. The second part discusses the use of fossil benthic foraminiferal assemblages as palaeoceanographic proxies from past cold‐water coral environments. The overview of previous observations demonstrates that benthic foraminifera are valuable tools to reconstruct past bottom‐water oxygenation, bottom‐water currents and surface productivity, all of which are key environmental variables controlling cold‐water coral growth. Moreover, the advantages of a detailed investigation of benthic foraminiferal assemblages within cold‐water coral environments are compared to other palaeoceanographic proxies. This study highlights that benthic foraminiferal assemblages are an often overlooked proxy within cold‐water coral environments, despite yielding valuable information.
... At smaller timescales, the paleo-bottom currents sculpt of these contourite drifts, so their climatic imprint is not well documented (Ercilla et al., 2002;López-González et al., 2019). In contrast, a large dataset of paleoclimate proxies is available for the Alboran Sea, documenting changes in oceanography, productivity, temperature, and redox and wind conditions of both surface and deep water masses at different timescales (Cacho et al., 1999(Cacho et al., , 2000(Cacho et al., , 2001Moreno et al., 2002Moreno et al., , 2004Moreno et al., , 2005Colmenero-Hidalgo et al., 2004;Martrat et al., 2004;Rogerson et al., 2005Rogerson et al., , 2008Sierro et al., 2005;Jiménez-Espejo et al., 2007;Combourieu-Nebout et al., 2009;Martín-Puertas et al., 2010;Nieto-Moreno et al., 2011;Fink et al., 2013;Rodrigo-Gámiz et al., 2014Ausín et al., 2015;Català et al., 2019;Bazzicalupo et al., 2020;among others). Still, certain aspects of the paleoceanographic evolution of the Western Mediterranean Sea over the last 25 cal. ...
... Two chemical element ratios (Zr/Al and Si/(Si + Al) ratios) served to characterize the chemical composition and to interpret oceanographic and environmental changes. The Zr/Al ratio has been previously used as a proxy for bottom currents in other regions (Bahr et al., 2014;Stow et al., 2018) and the Si/(Si + Al) ratio for dry versus humid conditions in the Alboran Sea (Moreno et al., 2005;Fink et al., 2013). The relative contents of these elements were measured on split core sediment sections at 1 cm intervals using an Avaatech X-ray fluorescence core scanner at the CORELAB of the University of Barcelona, obtaining higher sampling resolution than with grain-size analysis. ...
The Western Mediterranean Deep Water (WMDW), on its way out toward the Atlantic Ocean, has favored the formation of contourite drifts in the Alboran Sea (SW Mediterranean) since the opening of the Strait of Gibraltar. Resolving the nature of these deposits is crucial for reconstructing the WMDW variability at a millennial scale, deciphering its bottom current paleo-velocity, and establishing paleoclimatic implications over the last 25 cal. kyr BP. Two sediment cores retrieved from elongated separated and plastered contourite drifts formed along its path are investigated by means of multi-sedimentological data (terrigenous grain-size, sortable silt, terrigenous and carbonate sediment fluxes, bioturbation and ichnofabric changes), geochemical data (Zr/Al and Si/(Si + Al) ratios), chronostratigraphic data (δ¹⁸O, and ¹⁴C data) as well as statistical analyses (grain-size end-member modelling and spectral analysis). Integration of these data confirms the contouritic nature of Alboran drift deposits. The high-resolution paleocurrent records of the WMDW inferred from the sortable silt of contourite sequences led us to define two regimes in terms of WMDW flow energy. Regime 1 (weak to moderate velocity) defined by paleo-velocities of ⁓4 to 23 cm s⁻¹ is dominant during the last 24 cal. Kyr BP. Regime 2 (strong velocity) is characterized by estimated paleo-velocities of about ⁓36 cm s⁻¹ during Heinrich Stadial 2. The spectral analysis of bottom current proxies (sortable silt and Zr/Al ratio) matches four cyclic climatic signals (1900 yr, 2300 yr, 4000 yr, and 6100 yr), corroborating the occurrence of millennial-scale cyclicity. These cycles are related to atmospheric climate variability, in turn linked to variations in solar activity. Our results, when combined with published data from a neighboring NW Mediterranean contourite drift, provide for a better regional understanding of the WMDW millennial-scale dynamics.
... High surface productivity has also been found as a factor controlling cold-water coral growth (White et al., 2005;Eisele et al., 2011;Fink et al., 2013;Wienberg et al., 2022) in which case cold-water corals might be able to survive at greater depths. For cold-water coral reefs within a few hundred meters from the ocean surface (e.g., Norwegian reefs), wind-induced Ekman transport is likely an important food supply mechanism (Thiem et al., 2006). ...
Internal tides are known to be an important source of mixing in the oceans, especially in the bottom boundary layer. The depth of internal-tide generation therefore seems important for benthic life and the formation of cold-water coral mounds, but internal-tidal conversion is generally investigated in a depth-integrated sense. Using both idealized and realistic simulations on continental slopes, we found that the depth of internal-tide generation increases with increasing slope steepness and decreases with intensified shallow stratification. The depth of internal-tide generation also shows a typical latitudinal dependency. Using a global database of cold-water corals, we found that the depth-pattern of internal-tide generation is remarkably similar to the depth-pattern of cold-water corals globally: shallowest near the poles and deepest around the equator with a shoaling around 25 degrees South and North and shallower north of the equator than south of the equator. We further found that cold-water corals are, more than what would be expected by chance, associated to the (super)critical reflection of internal tides (i.e., situated on topography that is steeper than the internal tidal beam) and to trapped internal tides (i.e., above the critical latitude of 70 degrees for semidiurnal tides and 30 degrees for diurnal tides). The (super)critical reflection of internal tides and trapped internal tides therefore provide an interesting new angle of food supply mechanisms that has not yet been considered in cold-water coral studies. With climate change, stratification is expected to increase. Based on our results, this would cause a shoaling of internal-tide generation, possibly creating new shallower suitable habitat for cold-water corals on continental slopes.
... It is interesting to note that the disappearance of M. oculata from the Sciacca Banks overlapped with a similar phenomenon that occurred in the Alboran Sea (Trias-Navarro et al. 2021), where it is correlated to a time of increased agriculture activities in Morocco, causing enhanced fluvial sediment supply (McGregor et al. 2009). A sudden remarkable increase in the sedimentation rate (Fink et al. 2013) may have hampered coral growth at a local scale. ...
The sub-fossil red coral deposits of Sciacca (Sicily Channel) have attracted scientific attention for nearly 150 years. Their origin and formation have been long questioned and investigated, given the fact that they represent one of the most intriguing geobiological events ever to occur in the Mediterranean basin. Less attention was given to the paleo-community associated with the sub-fossil coral. Radiocarbon age determinations, in particular, were provided only for red coral, neglecting the possibility of understanding which species were simultaneously present in the coralline paleo-community and which was their role. The study of cemented coral rubble pieces revealed that Corallium rubrum covered the largest time interval (more than 3000 years) and was contemporary to many secondary epibionts over two millennia and to Madrepora oculata for about 500 years; this last finding suggested that an uncommon co-dominance between the two structuring species occurred in the nearby living communities. The lack of Fe–Mg deposits on the cemented coral rubbles coupled with the low bioerosion rate of the red coral skeletons by the demosponge Siphonodictyon coralliirubri (assessed through the analysis of the erosive paleo-scars) suggested that the deposits met with a rapid sediment cover-up. Moreover, for the first time, the analysis of a piece of cemented coral rubble of sub-fossil red coral coming from Sardinian waters confirmed that, albeit to a lesser extent, the conditions favouring the preservation of dead corals can occur also in different localities far from Sciacca.
... Key findings mark the final oscillations of the last glacial period (late HE-1 to Younger Dryas) with remarkable Saharan wind/aridity enhancement (Bout-Roumazeilles et al., 2007;Fink et al., 2013) (Fig. 13). This has been seen to be synchronous with strengthening and northward shift of north-westerly winds during stadials (Cacho et al., 2000;Moreno et al., 2002) and with higher NAO index in a modern situation (Moulin et al., 1997). ...
Lacustrine settings constitute a unique environment that preserves detailed expressions of allocyclic signals such as those of climate and tectonics. Possible decryption of these signatures stems from careful scrutiny of the sed- imentation dynamics (temporary base-level variations), lake-level fluctuations (accommodation), and resulting strata bounding surfaces that are used to build a conventional sequence stratigraphic framework. However, due to discrepancies between marine, to which this approach has been initially dedicated, and lacustrine settings (es- pecially regarding the physical scale), deciphering climate from tectonic forcing becomes unwieldy in such inte- rior basins. The present work deals with this challenge and provides insights from a case study where lacustrine sedimentation occurs on a tectonically active half-graben within a key climate region (Lake Ifrah, Northwest Af- rica). We conducted conventional sedimentological and high-resolution sequence-stratigraphic analyses, inte- grated with palaeolimnological proxies (geochemical elements and ostracod species). Up to five facies models (accounting for lithological domination, wind-driven energy, and lake-level state) and three lowest rank T-R se- quences, deposited since the Marine Isotope Stage-3 (MIS-3), have been identified. Periods with sustained high lake levels appear to be mainly precession-paced (as during MIS-3 and the Early Holocene), although the role of obliquity is shown to influence the hydrological budget as well. Furthermore, sedimentation dynamics are shown to respond to millennial timescale climate variability associated with North Atlantic cooling events (Dansgaard- Oeschger stadials, Heinrich Events) and, interestingly, to enhanced Saharan winds during the deglacial period. On the other hand, tectonism had a rather instantaneous effect on lake level and sedimentation. Two tectonic pulses marking instantaneous differential hanging-wall subsidence have triggered a sharp drop in relative lake level, hence conditioning a forced regression.
We highlight the importance of the conventional high-resolution sequence stratigraphy in shaping our under- standing of the cyclic interplay between orbital/sub-orbital and tectonic forcings, so as the resulting sedimenta- tion dynamics and lake-level cycles in lacustrine settings. We stress the role of the forced regression concept and associated systems tract and bounding surfaces, as well as the importance of using ostracods and geochemical proxies to trace transgressions and cryptic surfaces with sequence-stratigraphic significance, such as the maxi- mum flooding surface, in lacustrine settings.
... Key findings mark the final oscillations of the last glacial period (late HE-1 to Younger Dryas) with remarkable Saharan wind/aridity enhancement Fink et al., 2013) ( Fig. 13). This has been seen to be synchronous with strengthening and northward shift of northwesterly winds during stadials (Cacho et al., 2000; and with higher NAO index in a modern situation (Moulin et al., 1997). ...
... Such morpho-sedimentary features typically form close to mounds associated with contourite drifts due to local turbulence and enhanced current speeds (e.g. De Mol et al., 2002;Grasmueck et al., 2006;Fink et al., 2013;L€ udmann et al., 2016). ...
The study examines bioclastic carbonate contourites that arise from the broad spectrum of bottom‐current related sedimentary processes ranging from deposition to erosion. The result of the intermittent accumulation of sediment are thin and condensed successions with abundant hiatuses. Such bottom‐current deposits are poorly known, since the broadly accepted contourite‐facies model, the bi‐gradational sequence, characterizes environments of contourite depositional systems as a continuous accretion of fine‐grained siliciclastic sediments. To increase current understanding of the carbonate facies within hiatal contourite records, the Eifelian–Frasnian of the Tafilalt Platform in Morocco was investigated. The succession is divided into five facies associations that are interpreted to reflect pelagic sedimentation and deposition from bottom currents on a contourite terrace, a gently inclined section of the upper slope of Gondwana shaped by a water‐mass interface. Contourite deposition was mainly controlled by oxic clear‐water currents (documented by moderately to completely bioturbated limestones with abundant hydrogenetic ferromanganese nodules, and low organic‐carbon contents), at times also by an anoxic water mass (featured by organic‐rich coquinas with absent to sparse bioturbation and predominantly syngenetic framboidal pyrites). Biostratigraphic data and the overall depositional architecture display palaeoceanographic hydrodynamic processes associated with a shifting water‐mass interface. The inner terrace was characterized by an alongslope contourite channel and a small mounded drift at its downslope margin. Energetic bottom currents furthermore caused abraded surfaces, i.e. plain areas of non‐deposition and localized erosion, and sandy condensation layers. The microfacies reflects repeated alternation between suspension deposition, winnowing of fines, bedload traction, dynamic sediment bypassing and reworking, together with concomitant seafloor cementation. Coquinas of mainly planktonic and nektonic organisms are identified as integral parts of bi‐gradational contourite sequences showing inverse and normal grading. Hiatal lag concentrations of carbonate intraclasts, ferromanganese nodules and conodonts often drape hardgrounds and erosional surfaces at the midpoint of these frequently incomplete sequences. This Devonian case provides the opportunity to investigate the spatial and temporal variability of the bed‐scale contourite sequence, also with regard to the drift‐scale depositional architecture. In addition, the identified high‐resolution record is a starting point for unravelling the pattern of oceanic circulation in the Devonian greenhouse world.
... Living CWC (mostly Madrepora oculata) have been recorded on Seco de los Olivos ( However, the amount of coral rubble detected on the seafloor is far beyond what could be produced by the scattered contemporary colonies. Very high mound aggradation rates have been recorded during the last deglaciation and the Early Holocene (Fink et al., 2013;Wienberg, 2019) and this suggests that existing coral rubble deposits are relicts of former and more favourable living conditions for CWC. ...
A new species of gastropod, Episcomitra angelesae (Neogastropoda: Mitridae), is described from specimens collected in the upper bathyal level of the Alboran Sea (Seco de los Olivos and Alboran Ridge). The new species is compared with other similar species known from the Atlanto-Mediterranean area, including Episcomitra zonata (Marryat, 1819) and Isara turtoni (Watson, 1890). The habitat of this new species, hard substrate with coral rubble patches at 250-320 m depth on submarine elevations, is very unusual in the Mediterranean Sea and is described based on Remotely Operated Vehicle video footage. The amount of coral rubble on the type locality is disproportionate to the very few live coral colonies found in the vicinity, and is assumed to be relict of former hydrological conditions.
... The compilation is updated from a personal raw data compilation by O. Cartapanis, supplemented with data from the PALMOD compilation (Jonkers et al., 2020), and additional published and unpublished (cores MSM58-52-02 and core KNR197-10_GGC5) deglacial sites. All data were quality-controlled revisiting the original publications (Abrantes et al., 1998(Abrantes et al., , 2018Bertram et al., 1995;Beveridge et al., 1995;Bickert and Mackensen, 2004;Boyle and Keigwin, 1985;Cacho et al., 2006;Came et al., 2008;Chi and Mienert, 2003;Collins et al., 2010;Curry et al., 1988Curry et al., , 1999Curry and Oppo, 1997;Dickson et al., 2009;Duplessy, 1982Duplessy, , 1988Elliot, 2017;Elmore and Wright, 2011;Elmore et al., 2015;Fink et al., 2013;Freudenthal et al., 2002;Frigola et al., 2008;Gersonde et al., 2003;Hagen et al., 2002;Hagen and Keigwin, 2017;Hillaire-Marcel et al., 1994;Hoffman and Lund, 2012;Hoogakker et al., 2015;Hüls, 1999;Jansen and Veum, 1990;Jonkers et al., 2015;Jung, 1996;Keigwin and Jones, 1994;Keigwin, 2004;Keigwin et al., 1991;Keigwin and Lehman, 1994;Keigwin and Schlegel, 2002;Keigwin and Swift, 2017;Kiefer, 1998;Labeyrie et al., 1995Labeyrie et al., , 1999Labeyrie, 1996;Lebreiro et al., 2009;Little et al., 1997;Lund et al., 2015;Lynch-Stieglitz et al., 2011;Mackensen, 2001;Manighetti et al., 1995;Members, 1976Members, , 2004Members, , 2004Middleton et al., 2016Middleton et al., , 2018Millo, 2005;Millo et al., 2008;Mulitza et al., 2008Mulitza et al., , 2017Nam, 1997;Oppo et al., 2006Oppo et al., , 2015Oppo and Fairbanks, 1990;Oppo and Horowitz, 2000;Oppo and Lehman, 1995;Pichevin et al., 2005;Praetorius et al., 2008;Repschl€ ager et al., 2015a;Richter, 1998;Rickaby and Elderfield, 2005;Sarnthein et al., 1988Sarnthein et al., , 1994Schwab et al., 2012;Shimmield, 2004;Sierro et al., 2005;Slowey and Curry, 1995;Telesi nski et al., 2014;Thornalley et al., 2010Thornalley et al., , 2011Tiedemann, 1991;Tjallingii et al., 2008;van Kreveld et al., 2000;Vidal et al., 1997;Voelker et al., 2006;Vogelsang et al., 2001;Voigt et al., 2017;Waelbroeck et al., 2001Waelbroeck et al., , 2006Waelbroeck et al., , 2011Waelbroeck et al., , 2019Weinelt, 1993;Weldeab et al., 2016;Willamowski, 1999;Zabel et al., 2001;Zahn et al., 1987;Zhang et al., 2015). The detailed list for the quality check is given in the supplementary information and included revisiting the original data, controlling first authorship of data, species names standardization, control of potential species offset corrections and age model revisions. ...
Deepwater circulation significantly changed during the last deglaciation from a shallow to a deep-reaching overturning cell. This change went along with a drawdown of isotopically light waters into the abyss and a deep ocean warming that changed deep ocean stratification from a salinity-to a temperature-controlled mode. Yet, the exact mechanisms causing these changes are still unknown. Furthermore, the long-standing idea of a complete shutdown of North Atlantic deepwater formation during Heinrich Stadial 1 (HS1) (17.5–14.6 kyr BP) remains prevalent. Here, we present a new compilation of benthic δ¹³C and δ¹⁸O data from the North Atlantic at high temporal resolution with consistent age models, established as part of the international PAGES working group OC3, to investigate deepwater properties in the North Atlantic. The extensive compilation, which includes 105 sediment cores, reveals different water masses during HS1. A water mass with heavy δ¹³C and δ¹⁸O signature occupies the Iceland Basin, whereas between 20 and 50°N, a distinct tongue of ¹⁸O depleted, ¹³C enriched water reaches down to 4000 m water depths. The heavy δ¹³C signature indicates active deepwater formation in the North Atlantic during HS1. Differences in its δ¹⁸O signature indicate either different sources or an alteration of the deepwater on its southward pathway. Based on these results, we discuss concepts of deepwater formation in the North Atlantic that help to explain the deglacial change from a salinity-driven to a temperature-driven circulation mode.
... sediment, foraminifera are powerful tools to understand past CWC environments (e.g., Rüggeberg et al., 2007;Stalder et al., 2014;Fentimen et al., 2020a). The increasing knowledge of the ecological requirements of living, recent and sub-recent benthic foraminifera from different NE Atlantic D. pertusum sites (e.g., Margreth et al., 2009Margreth et al., , 2011Schönfeld et al., 2011;Morigi et al., 2012;Spezzaferri et al., 2013;Fink et al., 2013;Smeulders et al., 2014;Stalder et al., 2014;Fentimen et al., 2018Fentimen et al., , 2020b is the basis of our paleoecological interpretations inferred from fossil assemblages. ...
Benthic foraminiferal assemblage data have been derived from a marine sediment core collected in a cold-water coral (CWC) site off northwest Scotland (near the Wyville Thomson Ridge - WTR). The record covers the last glacial period to the late Holocene. Our reconstructions enable to better constrain the paleoenvironmental changes that took place in the study area since the last glacial time and define the environmental conditions that allowed the onset, formation and decline of CWCs in the area. The sedimentary record was characterized by three distinct foraminiferal assemblages, dominant during the pre-coral time interval (i and ii) and the coral period (iii): (i) the “Glacial” assemblage (>13 cal ka BP) was characterized by the dominance of C. refulgens and Discanomalina coronata. Low foraminiferal densities and diversities indicated unfavorable ecological conditions (i.e., low temperature and food availability, coarse substrate) that were most likely related to the extended British Ice Sheet; (ii) the “Deglacial-Early Holocene” assemblage (~13–9 cal ka BP) was characterized by the cassidulinids-Lobatula lobatula association, indicating a progressive increase of organic matter content and influx of warm and saline North Atlantic surface waters. We hypothesize that these were the main environmental factors that thereafter allowed the settlement of CWCs in the WTR area around 9 cal ka BP; (iii) the “Holocene” (<9 cal ka BP) assemblage was characterized by the cohabitation of diverse epifaunal species (e.g., Rosalina globularis) present when CWCs were highly abundant, and infaunal species (e.g., Trifarina angulosa) when corals were less frequent. The periods recording high presence of T. angulosa after 9 ka cal BP were interpreted as indicating a higher contribution of Eastern North Atlantic Waters during periods of retracted Subpolar Gyre (SPG), affecting probably the efficiency of food export to the seafloor.
... Improved mapping techniques (such as multibeam), direct bottom inspection through TV-equipped devices (for example, large box-corer), the assistance provided by ROV in selecting best potential sites, the availability of aptly drilling vessels and new coring techniques (for example MeBo: Freudenthal and Wefer 2007) have disclosed new horizons in the study of CWC by achieving georeferenced successions with their original stratigraphy. Thus, since the mid '90s the scenario has changed considerably and coring (piston, gravity and box) is routine on most research conducted on Atlantic (Dorschel et al. 2005;Rüggeberg et al. 2007;Hebbeln et al. 2008Hebbeln et al. , 2009Wienberg et al. 2009Wienberg et al. , 2010aWienberg et al. , b, 2018Frank et al. 2011a;Freiwald et al. 2011;Van Rooij et al. 2011;Douarin et al. 2013;Vandorpe et al. 2017) and Mediterranean CWC (Malinverno et al. 2010;Freiwald et al. 2011;Margreth et al. 2011;Fink et al. 2012Fink et al. , 2013Fink et al. , 2015Douarin et al. 2014;Titschack et al. 2016;Dubois-Dauphin et al. 2017). ...
... Additionally, the interplay between favourable bottom currents and climatic conditions could have influenced the complex CM development in different phases, possibly related to the last deglaciation (<5400 years) corresponding to the Late Holocene, as suggested by Fink et al. (2013) for the EMP mounds. ...
The seafloor of the Alboran Sea reflects its complex tectonic, sedimentary, and oceanography dynamics as a consequence of the geological context, involving interaction between the Eurasian and African plates, and oceanographic context, as it is where the Atlantic and Mediterranean waters meet. Their physiography has a semi-enclosed configuration characterized by two margins (the Spanish Iberian and North Africa—mostly Moroccan margins) enclosing deep basins. Tectonic activity is mainly attested by folds and faults that predominantly affect the central and eastern seafloor sectors, as well as numerous seamounts and fluid-flow features (pockmarks, mud volcanoes, and diapirs) that dot the seafloor. The sedimentary and oceanographic processes allow us to distinctly define two principal environments in the Alboran Sea: the shallow proximal margin (continental shelf); and the deep distal margin (continental slope and base of the slope) with the adjacent sub-basins. The shelf mostly comprises prodeltaic and infralittoral prograding wedges, with local bedform fields, submarine valleys, and wave-cut terraces. Coastal and fluvio-marine sedimentary processes, acting since the last glacial period, are responsible for these features. The deep marine environment is characterised by the ubiquity of contourites, whose continuity is interrupted by turbidite systems, canyons, and landslides. The alongslope action of the Mediterranean waters and their interfaces with the Atlantic water has been the main process governing transport, seafloor reworking, and sedimentation of contourites. Mass-movement processes are responsible for the formation of: (1) turbidite systems—turbidity flows and mass flows were dominant during the last glacial sea-level lowstand, evolving to dilute gravity flows during present interglacial high stand; and (2) landslides—the main triggering factors comprising over-steepening, seismicity, under consolidation due to overpressure by interstitial fluids, stratigraphy, and high sedimentation rates. Locally, still-undetermined biological activity in the Spanish and coral activity in the Moroccan margin generated fields of mounded bioconstructions. The seafloor morphology of the Alboran Sea offers interesting clues for assessing the main potential geological hazards, with tectonic seismicity and landslides (as well as their related tsunamis) being some of the most important potential hazards affecting coastal populations. In addition, the seafloor morphology in combination with assemblages of habitat-forming species enables habitat identification and mapping.
... Bathyal hard-bottom communities are patchily distributed over the heterogeneous and complex topography of the Alboran Sea basin and are restricted to prominent geomorphological features, such as seamounts, coral mounds, canyons and ridges Würtz 2012;Fink et al. 2013;Rovere and Würtz 2015). Information is still scanty and regards mostly Seco de los Olivos (Fig. 9.21), the Cabliers and Djibouti seamounts and the edge of the Alboran platform (Hebbeln et al. 2009;Pardo et al. 2011;Lo Iacono et al. 2012;de la Torriente et al. 2014de la Torriente et al. , 2018Gofas et al. 2014a, b;Corbera et al. 2019;Lo Iacono et al. 2019). ...
Benthic habitats, as well as their associated biota, have been studied in the Alboran Sea since the nineteenth century, with a very significant increase of knowledge in the last five decades. The geographical location of the Alboran Sea between three different biogeographical regions, the complex oceanography and the heterogeneous seafloor promote the coexistence of a wide diversity of habitat-forming species and, therefore, of habitat types. Some of these habitats host very complex communities in comparison to similar ones that are located northwards in the Atlantic Ocean or eastwards in the Mediterranean Sea. Moreover, some of those habitats are considered to be threatened or are experiencing very strong declines during this last decade and are probably extinct nowadays (e.g. Zostera marina beds). General knowledge of the associated biota is larger for those habitats of shallow waters in comparison to those of the deep sea and for those located in the northern sector in relation to those of the southern sector of the Alboran Sea. In most habitats, only some components of the associated biota have been studied, and there is a general lack of information for specific groups (e.g. meiofauna, Platyhelminthes, etc.).
... These mounds consist of coral-dominated intervals alternating with a mixed carbonate-siliciclastic matrix. They can be found in the Porcupine Seabight northwest of Ireland (De Mol et al., 2002;Huvenne, De Mol, & Henriet, 2003), the Gulf of Cadiz off the Moroccan coast (Foubert et al., 2008;Van Rooij et al., 2011;Wienberg et al., 2009Wienberg et al., , 2010 and the Alboran Sea in the western Mediterranean (Fink, Wienberg, De Pol-Holz, Wintersteller, & Hebbeln, 2013;Stalder et al., 2015Stalder et al., , 2018. These build-ups range from several tens to hundreds of metres in height, and their bases can reach a diameter of several kilometres (De Mol et al., 2002;Dorschel, Hebbeln, Rüggeberg, Dullo, & Freiwald, 2005;Huvenne et al., 2003;Van Weering, de Haas, de Stigter, Lykke-Andersen, & Kouvaev, 2003;Wheeler et al., 2007). ...
Cold‐water coral (CWC) mounds are build‐ups comprised of coral‐dominated intervals alternating with a mixed carbonate‐siliciclastic matrix. At some locations, CWC mounds are influenced by methane seepage, but the impact of methane on CWC mounds is poorly understood. To constrain the potential impact of methane on CWC mound growth, lipid biomarker investigations were combined with mineralogical and petrographic analyses to investigate the anaerobic oxidation of methane (AOM) and authigenic carbonate formation in sediment from a seep‐affected CWC mound in the Gulf of Cadiz. The occurrence of AOM was confirmed by characteristic lipids found within a semi‐lithified zone (SLZ) consisting of authigenic aragonite, high‐magnesium calcite and calcium‐excess dolomite. The formation of high‐Mg calcite is attributed to AOM, acting as a lithifying agent. Aragonite is only a minor phase. Ca‐excess dolomite in the SLZ and upper parts may be formed by organoclastic sulphate reduction, favouring precipitation by increased alkalinity. The AOM biomarkers in the SLZ include isoprenoid‐based archaeal membrane lipids, such as abundant glycerol dibiphytanyl glycerol tetraethers (GDGTs) dominated by GDGT‐2. The δ13C values of GDGT‐2, measured as ether‐cleaved monocyclic biphytanes, are as low as −100‰ versus V‐PDB. Further, bacterial dialkyl glycerol diethers with two anteiso‐C15 alkyl chains and δ13C values of −81‰ are interpreted as biomarkers of sulphate‐reducing bacteria. The lipid biomarker signatures and mineralogical patterns suggest that anaerobic methane‐oxidizing archaea of the ANME‐1 group thrived in the subsurface at times of slow and diffusive methane seepage. Petrographic analyses revealed that the SLZ was exhumed at some point (e.g. signs of bioerosion of the semi‐lithified sediment), providing a hard substrate for CWC larval settlement. In addition, this work reveals that AOM‐induced semi‐lithification likely played a role in mound stabilization. Lipid biomarker analysis proves to be a powerful tool to disentangle early diagenetic processes induced by microbial metabolisms.
... The recent intensification of deep-sea explorations in the Mediterranean Sea increased our knowledge on the distribution of Cold-Water Coral (CWC) habitats. After the discovery of the Santa Maria di Leuca (SML) coral bank in the northern Ionian Sea (Mastrototaro et al. 2002;Tursi et al. 2004;Longo et al. 2005;Taviani et al. 2005a;Taviani et al. 2005b) many other sites with living CWC have been recorded in the Mediterranean Sea (Taviani et al. 2017;Orejas et al. 2009;De Mol et al. 2012;Calcinai et al. 2013;Fink et al. 2013;Angeletti et al. 2014;Fabri et al. 2014;Mytilineou et al. 2014;Fanelli et al. 2017) allowing a fine scale mapping of CWC habitats. These findings have stimulated targeted research on ecological and biological aspects of these habitats, confirming their importance as collectors of biodiversity and rare species. ...
Here we describe two new species of deep-sea sponges collected during the exploration of Cold-Water Coral (CWC) banks discovered in the Nora and Coda Cavallo canyons (north-eastern and south coast of Sardinia respectively). Poecillastra tavianii n. sp. differs from the other congeneric species mainly for the dicho- and mesodichotriaenes, never observed in the genus, and the abundance and variety of spirasters. Hymedesmia (Hymedesmia) quadridentata n. sp. is characterized by the presence of two types of chelae. In particular, the unguiferate chelae (round shaft and four teeth at both extremities) represent a peculiar character of the species. Our contribution increases the number of sponge fauna associated to the best known Central Mediterranean CWC habitats to 98 improving the still scant knowledge on the biodiversity of the Mediterranean CWC habitats.
... Moreover, steeply sloping substrates and high-velocity currents can also prevent the burial of the CWCs by sediments. Additionally, seawater temperatures (Freiwald, 2002), dissolved oxygen concentrations (Fink et al., 2012;Wienberg et al., 2018) and depth of the aragonite saturation horizon (Guinotte et al., 2006) discovered in the north-eastern (NE) Atlantic Ocean (e.g., Fosså et al., 2002Fosså et al., , 2005Foubert et al., 2005;Somoza et al., 2014;van Bleijswijk et al., 2015;Raddatz et al., 2016;Wienberg et al., 2018), including the Mediterranean Sea (e.g., Remia and Taviani, 2005;Taviani et al., 2005Taviani et al., , 2017Fink et al., 2013) and the western Atlantic Ocean (e.g., Breeze et al., 1997;Watling and Auster, 2005;Hebbeln et al., 2014;Matos et al., 2017). Much research has focused on the NE Atlantic, in particular in the Porcupine Seabight and Rockall Bank areas along the Irish and UK coastal margins (e.g., Rüggeberg et al., 2007;Wheeler et al., 2011;van Bleijswijk et al., 2015;Bonneau et al., 2018), where more than 1000 thriving CWC mounds have been identified (Roberts et al., 2006). ...
Cold-water corals (CWCs) were found to occur in association with authigenic carbonates in a cold seep area on the northern continental slopes of the South China Sea (SCS). The taxa identified were: Balanophyllia (Balanophyllia) sp., Balanophyllia (Eupsammia) sp., Lochmaeotrochus sp., Enallopsammia sp., Crispatotrochus sp.1 and Crispatotrochus sp.2. The δ13C (−7.36‰ to −1.15‰, V-PDB) and 87Sr/86Sr ratios (0.709126–0.709184) indicated that CWC aragonite skeletons had been precipitated from seawater without the involvement of seeping fluids. The presence and growth of CWCs on the slopes of the submarine seamounts in the south-western (SW) Dongsha area could be directly linked with the hard substrates provided by exhumed hydrocarbon-imprinted authigenic carbonates and fed by the food particles enhanced by high-velocity internal tides and near-bottom currents. A multi-step process for CWC colonization was proposed that encompassed cold-seepage processes as a driver for hard-substrate generation of CWC, as well as the subsequent settlement and maintenance of CWC larvae under the persistent influence of bottom currents.
... Based on the available data, also including seismic records crossing the area and imaging its internal structure (Lo Iacono et al. 2011), the sinuous feature along the Chella eastern ridge most probably corresponds to a CWC mound, up to 60 m tall. Similar cold-water carbonate bioconstructions have already been described in the same basin, south of the Chella Bank (Cabliers CWC mound: Lo Iacono et al. 2016Iacono et al. , 2018a; East Melilla CWC Mounds: Fink et al. 2013, Wienberg, this volume; West Melilla CWC Mounds: Lo Iacono et al. 2014). ...
Habitat mapping is increasingly considered as a reliable and efficient methodology to explore and represent the complexity and extent of benthic communities. Providing a full-coverage spatial perspective of habitat heterogeneity is becoming an essential tool in science-based management of natural resources, specifically regarding vulnerable marine ecosystems such as cold-water corals. Here we present two case studies, where we revisit known cold-water coral areas of the Mediterranean Sea and where we apply original habitat mapping techniques. The areas correspond to the Chella Bank, in the Alborán Sea, and the Santa Maria de Leuca cold-water coral province, in the Ionian Sea. The Chella Bank is one of a series of volcanic banks and knolls located in the western Mediterranean that have been described as geologic features hosting vulnerable marine ecosystems. The cold-water coral province off Santa Maria de Leuca represents one of the largest known occurrences of living reef-forming cold-water coral species (i.e. Lophelia pertusa and Madrepora oculata) in the Mediterranean Sea, where corals grow on the exposed summits and flanks of mound-like structures (up to 300 m wide and 25 m high) associated with mass wasting events. Both cases adopt a holistic and integrated study of the environmental characteristics (geology and oceanography) of the observed benthic habitats and aim to map their extent using supervised automated classifications. Multibeam swath bathymetry, the derived acoustic backscatter, sidescan sonar, video footage gathered with a remotely operated vehicle, photo stills from underwater drop camera, and CTD casts where available, have been used together to identify the geological and oceanographic processes that most likely are responsible for the distribution of the observed cold-water corals and associated benthic communities.
... Improved mapping techniques (such as multibeam), direct bottom inspection through TV-equipped devices (for example, large box-corer), the assistance provided by ROV in selecting best potential sites, the availability of aptly drilling vessels and new coring techniques (for example MeBo: Freudenthal and Wefer 2007) have disclosed new horizons in the study of CWC by achieving georeferenced successions with their original stratigraphy. Thus, since the mid '90s the scenario has changed considerably and coring (piston, gravity and box) is routine on most research conducted on Atlantic (Dorschel et al. 2005;Rüggeberg et al. 2007;Hebbeln et al. 2008Hebbeln et al. , 2009Wienberg et al. 2009Wienberg et al. , 2010aWienberg et al. , b, 2018Frank et al. 2011a;Freiwald et al. 2011;Van Rooij et al. 2011;Douarin et al. 2013;Vandorpe et al. 2017) and Mediterranean CWC (Malinverno et al. 2010;Freiwald et al. 2011;Margreth et al. 2011;Fink et al. 2012Fink et al. , 2013Fink et al. , 2015Douarin et al. 2014;Titschack et al. 2016;Dubois-Dauphin et al. 2017). ...
Atlantic-type scleractinian cold-water corals occur in the Quaternary of the Mediterranean basin. Most fossil evidence on-land is Early Pleistocene in age, and occurs in peninsular Italy, Sicily and on some Greek islands, whilst submerged situations are by large late Pleistocene. According to circumstances, the mode of preservation of fossil cold-water coral varies sensibly (from loose corals to micritic limestones) what affects the level of confidence of the paleoecological reconstruction. All known situations point about a bathyal setting for such cold-water coral hosting deposits in the Mediterranean basin, but under many respects the geological record of cold-water coral paleoenvironments is yet largely underworked. Research developments are discussed, with special emphasis on the widespread submarine occurrences which prevail over the on-land cold-water coral legacy.
Internal tides are known to be an important source of mixing in the oceans, especially in the bottom boundary layer. The depth of internal-tide generation therefore seems important for benthic life and the formation of cold-water coral mounds, but internal-tide conversion is generally investigated in a depth-integrated sense. Using both idealized and realistic simulations on continental slopes, we found that the depth of internal-tide generation increases with increasing slope steepness and decreases with intensified shallow stratification. The depth of internal-tide generation also shows a typical latitudinal dependency related to Coriolis effects. Using a global database of cold-water corals, we found that, especially in Northern Hemisphere autumn and winter, the global depth pattern of internal-tide generation correlates (rautumn = 0.70, rwinter = 0.65, p < 0.01) with that of cold-water corals: shallowest near the poles and deepest around the Equator, with a decrease in depth around 25° S and N, and shallower north of the Equator than south. We further found that cold-water corals are situated significantly more often on topography that is steeper than the internal-tide beam (i.e. where supercritical reflection of internal tides occurs) than would be expected from a random distribution: in our study, in 66.9 % of all cases, cold-water corals occurred on a topography that is supercritical to the M2 tide whereas globally only 9.4 % of all topography is supercritical. Our findings underline internal-tide generation and the occurrence of supercritical reflection of internal tides as globally important for cold-water coral growth. The energetic dynamics associated with internal-tide generation and the supercritical reflection of internal tides likely increase the food supply towards the reefs in food-limited winter months. With climate change, stratification is expected to increase. Based on our results, this would decrease the depth of internal-tide generation, possibly creating new suitable habitat for cold-water corals shallower on continental slopes.
Framework-forming cold-water corals (CWCs) are ecosystem engineers that build mounds in the deep sea that can be up to several hundred metres high. The effect of the presence of cold-water coral mounds on their surroundings is typically difficult to separate from environmental factors that are not affected by the mounds. We investigated the environmental control on and the importance of ecosystem engineering for cold-water coral reefs using annotated video transect data, spatial variables (MEMs), and hydrodynamic model outputs in a redundancy analysis and with variance partitioning. Using available hydrodynamic simulations with cold-water coral mounds and simulations where the mounds were artificially removed, we investigated the effect of coral mound ecosystem engineering on the spatial configuration of reef habitat and discriminated which environmental factors are and which are not affected by the mounds. We find that downward velocities in winter, related to non-engineered environmental factors, e.g. deep winter mixing and dense-water cascading, cause substantial differences in reef cover at the broadest spatial scale (20–30 km). Such hydrodynamic processes that stimulate the food supply towards the corals in winter seem more important for the reefs than cold-water coral mound engineering or similar hydrodynamic processes in summer. While the ecosystem-engineering effect of cold-water corals is frequently discussed, our results also highlight the importance of non-engineered environmental processes. We further find that, due to the interaction between the coral mound and the water flow, different hydrodynamic zones are found on coral mounds that likely determine the typical benthic zonations of coral rubble at the mound foot, the dead coral framework on the mound flanks, and the living corals near the summit. Moreover, we suggest that a so-called Massenerhebung effect (well known for terrestrial mountains) exists, meaning that benthic zonation depends on the location of the mound rather than on the height above the seafloor or water depth. Our finding that ecosystem engineering determines the configuration of benthic habitats on cold-water coral mounds implies that cold-water corals cannot grow at deeper depths on the mounds to avoid the adverse effects of climate change.
Deep-sea explorations performed over the last two decades have shown evidence of abundant living cold-water coral communities in the Mediterranean Sea. Many submarine canyons, escarpments, seamounts, and outer continental shelf and slope areas support communities dominated by scleractinian cold-water corals or coral gardens composed of a diverse fauna of octocoral and black coral species. Other areas across the Mediterranean Sea show evidence of past prosperity of these communities expressed by accumulations of fossil cold-water corals. Here, we review the knowledge of the present and past occurrence of cold-water corals in the Mediterranean Sea, highlighting specific features and discussing the threats that they are exposed to under high human-induced pressure in this semi-enclosed basin.
We present the first version of the Ocean Circulation and Carbon Cycling (OC3) working group database, of oxygen and carbon stable isotope ratios from benthic foraminifera in deep ocean sediment cores from the Last Glacial Maximum (LGM, 23-19 ky) to the Holocene (<10 ky) with a particular focus on the early last deglaciation (19-15 ky BP). It includes 287 globally distributed coring sites, with metadata, isotopic and chronostratigraphic information, and age models. A quality check was performed for all data and age models, and sites with at least millennial resolution were preferred. Deep water mass structure as well as differences between the early deglaciation and LGM are captured by the data, even though its coverage is still sparse in many regions. We find high correlations among time series calculated with different age models at sites that allow such analysis. The database provides a useful dynamical approach to map physical and biogeochemical changes of the ocean throughout the last deglaciation.
Framework-forming scleractinian cold-water corals (CWCs) act as ecosystem engineers, building and supporting biodiversity hotspots in the deep sea worldwide. While spatial patterns and drivers of species distributions have been evaluated on modern CWC reefs, little is known about how reef diversity is affected by habitat variability over geologic time – the scale at which CWC reefs initiate, thrive, and decline. Using three CWC reef sediment cores as species diversity archives, we investigated temporal trends of molluscan diversity over the last ~13 kyr from a CWC mound in the Alboran Sea (western Mediterranean Sea) to evaluate (a) how spatial patterns of CWC associated diversity are recorded in reef sediments, (b) the potential of CWC reefs as biodiversity hotspots when coral growth is flourishing and when it is not, and (c) which palaeoceanographic conditions or habitat characteristics may be driving biodiversity. Our results reveal that at the ecosystem scale ecological differences between CWC habitats are more pronounced than ecological signatures of molluscan assemblages associated with intervals of CWC framework (flourishing growth) or non-framework (negligible CWC growth). However, within habitats, significant differences emerge between these assemblages with lower molluscan diversity associated with flourishing CWC growth. Significant negative correlations between molluscan diversity and palaeoceanographic conditions conducive for CWC growth (high food availability, strong hydrodynamics, optimal bottom-water temperatures and salinities, and high aggradation rates indicative of flourishing CWC growth also imply that CWC growth and relevant environmental conditions contribute to reduced molluscan diversity. Additionally, high coral volume, used here as a proxy for habitat structural complexity, is positively correlated with molluscan diversity just as high habitat complexity is in living CWC reefs. Altogether, these patterns detected over geologic time resemble those observed spatially across living CWC reefs today – where competition with resources, particularly food, prevents high reef biodiversity in the immediate vicinity of dense living CWC colonies. Overall, our study demonstrates that (1) ecological paradigms of living CWCs are preserved in their sedimentary record, (2) flourishing CWC growth and conditions promoting CWC growth drive habitat-scale diversity patterns, and (3) a geological approach can be applied to study long-term diversity dynamics in CWC ecosystems.
Framework-forming cold-water corals (CWC) are ecosystem engineers, building and supporting deep-sea biodiversity hotspots worldwide. While spatial patterns and drivers of species distributions have been evaluated on modern CWC reefs, little is known how reef biodiversity is affected by habitat variability over geologic time – the scale at which CWC reefs initiate, thrive, and decline. Using three CWC reef sediment cores as species diversity archives, we investigated temporal trends of molluscan diversity over the last ~13 kyr from a CWC mound in the Alboran Sea to evaluate (a) how spatial patterns of CWC-associated diversity are recorded in reef sediments, (b) the potential of CWC reefs as biodiversity hotspots when coral growth is flourishing and when it is not, and (c) which palaeoceanographic conditions or habitat characteristics may be driving biodiversity. Our results reveal that at the ecosystem scale differences in molluscan assemblages are more pronounced between CWC habitats than between intervals of CWC framework (flourishing growth) and non-framework (negligible CWC growth). However, within habitats, significant differences emerge between these assemblages: lower molluscan diversity is associated with flourishing CWC growth. Significant negative correlations between molluscan diversity and palaeoceanographic conditions conducive for CWC growth (high food availability, strong hydrodynamics, optimal bottom-water temperatures and salinities, high aggradation rates indicative of flourishing CWC growth) also imply that CWC growth and relevant environmental conditions contribute to reduced molluscan diversity. Altogether, these patterns detected over geologic time resemble those observed spatially across living CWC reefs today – where competition with resources, particularly food, prevents high reef biodiversity near dense living CWC colonies. Our study demonstrates that (1) ecological paradigms of living CWC are preserved in their sedimentary record, (2) flourishing CWC growth and conditions promoting CWC growth drive habitat-scale diversity patterns, and (3) a geological approach can be applied to study long-term diversity dynamics in CWC ecosystems.
Session No. 139
D23. Paleontology: Recent Developments in Diversity, Extinction, and Origination
Tuesday, 11 October 2022
We present a global atlas of downcore foraminiferal oxygen and carbon isotope ratios available at https://doi.org/10.1594/PANGAEA.936747
(Mulitza et al., 2021a). The database contains 2106 published and previously unpublished stable isotope downcore records with 361 949 stable isotope
values of various planktic and benthic species of Foraminifera from 1265 sediment cores. Age constraints are provided by 6153 uncalibrated
radiocarbon ages from 598 (47 %) of the cores. Each stable isotope and radiocarbon series is provided in a separate netCDF file containing
fundamental metadata as attributes. The data set can be managed and explored with the free software tool PaleoDataView. The atlas will provide
important data for paleoceanographic analyses and compilations, site surveys, or for teaching marine stratigraphy. The database can be updated with
new records as they are generated, providing a live ongoing resource into the future.
Cold-water corals are key species of benthic ecosystems, sensitive to changes in climate and capable of recording them in the chemical composition of their skeletons. The study of cold-water coral mound development in relation to palaeoceanographic variations during the Pleistocene and Holocene stages in the Mediterranean Sea has mainly been focussed in the Alboran Sea (Western Mediterranean). The present study describes the coral deposits and corresponding ages of 3 gravity cores, acquired from the newly discovered Tunisian Coral Mound Province (Central Mediterranean), which comprises several ridge-like mounds. All the cores acquired displayed dense coral deposits, dominated by Desmophyllum pertusum fragments embedded within a muddy sediment matrix. Overall, 64 coral samples have been dated with the UTh laser ablation MC-ICP-MS method, revealing corals of mostly Pleistocene age ranging from ~MIS 11 to 8.4 ka BP. Although coral mound formation was reduced for most of the last 400 kyr, a main stage of pronounced mound formation occurred during the last glacial period, which contrasts to the findings previously published for coral mounds in other regions of the Mediterranean Sea. Coral mound formation during the last glacial was most likely associated with a colder seawater temperature than the one observed in the present-day, an increased surface productivity and an appropriate depth of the interface between Atlantic Waters and Levantine Intermediate Waters. The combination of the data acquired here with that of previous mound formation studies from the Alboran Sea also suggests that cold-water coral mounds located at greater depths develop at slower rates than those found in shallower settings.
Benthic foraminifera (protists with biomineralized tests) coupled with geochemical proxies are used for the first time to characterize present oceanographic conditions occurring in cold-water coral ecosystems (CWC) in the eastern Alboran Sea (Brittlestar Ridge and Cablier Mound), western Mediterranean Sea. Quantitative data on living (stained) benthic foraminifera from 5 box cores retrieved during the MD194 cruise on the RV Marion Dufresne reveal that these organisms are more diverse in presence of corals, where more numerous ecological niches occur than they are in pelagic adjacent sediments. These data confirm that CWC can be considered as “diversity hotspots” also for benthic foraminifera.
Geochemical characterization shows that these sediments contain relatively fresh (labile) organic matter but also a reworked refractory component. In particular, the total organic carbon and the δ¹³Corg values suggest that some of the organic matter may be a mixture of marine and reworked particulate organic matter, compared to typical values from temperate phytoplankton. The δ¹⁵N of the organic fraction suggests that important atmospheric N2-fixation and degradation processes occur in the region.
Finally, our results show that a more effective advection of freshly exported particulate organic matter from the surface waters occur at the mound top rather than at the mound base or off-mound allowing some coral colonies to survive on the top of mounds in this region. The mud layer covering the coral rubble debris may suggest that the Brittlestar Ridge is today exposed to siltation preventing the growth of corals at the mound base or off-mound.
The Alboran Sea displays the highest values of animal species richness in the European seas, and invertebrates comprise the bulk of this diversity. In this chapter, the importance of invertebrates as the main components of biodiversity (sometimes neglected) is highlighted through numerous examples of representative species in this Mediterranean basin. Almost all large invertebrate groups (Phyla) are present in the Alboran Sea, and they play vital roles as basic links in the trophic web and participate one way or another in all oceanic ecological processes. We attempt to offer an overview of these animal groups and of their peculiar adaptations or life styles, focused on species that have their most important populations in this area. Despite focusing on the most emblematic, conspicuous, abundant or threatened species (very few of them really protected), we also stress the importance of small, rare, inconspicuous and little-known species and provide some striking examples. A list of the species originally described in the Strait of Gibraltar and Alboran Sea in the last decades is provided. Finally, it is advised that this natural richness is in danger since the conservation status of many species is very worrying, due to the regression of many populations and to some mass mortality events.
Palaeoclimate data hold the unique promise of providing a long-term
perspective on climate change and as such can serve as an important
benchmark for climate models. However, palaeoclimate data have generally
been archived with insufficient standardisation and metadata to allow for
transparent and consistent uncertainty assessment in an automated way.
Thanks to improved computation capacity, transient palaeoclimate simulations
are now possible, calling for data products containing multi-parameter time
series rather than information on a single parameter for a single time
slice. Efforts are underway to simulate a complete glacial–interglacial
cycle using general circulation models (https://www.palmod.de/, last access: 6 May 2020), and to confront these
simulations with palaeoclimate data, we have compiled a multi-parameter
marine palaeoclimate data synthesis that contains time series spanning 0 to
130 000 years ago. We present the first version of the data product that
focuses exclusively on time series for which a robust chronology based on
benthic foraminifera δ18O and radiocarbon dating is available.
The product contains 896 time series of eight palaeoclimate parameters from
143 individual sites, each associated with rich metadata, age–depth model
ensembles, and information to refine and update the chronologies. This
version contains 205 time series of benthic foraminifera δ18O;
169 of benthic foraminifera δ13C; 131 of seawater temperature;
174 and 119 of planktonic foraminifera δ18O and δ13C; and 44, 38 and 16 of carbonate, organic carbon and biogenic silica
content, respectively. The data product is available in three formats (R,
LiPD and netCDF) facilitating use across different software and operating
systems and can be downloaded at https://doi.org/10.1594/PANGAEA.908831 (Jonkers et al., 2019). This
data descriptor presents our data synthesis strategy and describes the
contents and format of the data product in detail. It ends with a set of
recommendations for data archiving.
Impressive seafloor structures formed by cold-water corals characterise parts of the seafloor in the southeastern Alborán Sea, forming the East Melilla Cold-Water Coral Mound Province. These geomorphological features are composed of a mixture of cold-water coral fragments and hemipelagic sediments, displaying typical coral mound deposits. Along a N-S transect across the Mediterranean Moroccan margin, extending for up to ~25 km, three belts of very differently shaped mound structures occur. Their morphologies and dimensions vary considerably, ranging from up to 20-km-long and 150-m-high steep ridges to elongated and arcuate mounds of a few hundred meters in diameter and up to 40 m in height. Obviously, different interacting drivers, including tectonics and hydrodynamics, must have been involved at a variable scale in shaping these fascinating submarine landscapes in the past.
Despite our limited current knowledge on fossil Mediterranean deep-sea corals, data collected so far hint at a strong influence of climate modifications on the distribution and diversity of these organisms through the Quaternary. Several species still living in the North Atlantic became extinct in the Mediterranean Sea at the Pleistocene-Holocene boundary, and the highest cold-water coral mound accretion rates known so far occurred during the last deglacial phase. Thermal variations of deep-sea waters have certainly affected distribution and survival of the most stenothermic coral species. However, changes in other environmental variables (such as current intensity, food supply and sediment rate, oxygenation), influenced by climate forcing, seem to have highly contributed to the decreased diversity of deep-sea corals and reduced accretion rate of coral mounds through the Quaternary. In order to precisely correlate the observed modifications of paleoassemblages with climate fluctuations, additional research effort needs to be conducted on both emerged and submerged coral deposits.
Dynamic bottom current regimes govern cold-water corals as well as contourites. We provide an overview of the general aspects of both research fields, with specific attention to the Mediterranean Sea region, which has the particularity to be a climatically-sensitive mid-latitude semi-enclosed basin. In this area there are many examples of along-slope contourite deposits (known as contourite drifts), typically with an along-slope, elongated mounded shape adjacent to a concave moat. Likewise, a number of thriving coral sites, together with sparse occurrences, are present in the central and western Mediterranean, with large coral mounds known so far only in the Alborán Sea. In the Mediterranean Sea both contourite drift and cold-water corals seem mainly related to the Levantine Intermediate Water, but their strict co-existence has still to be ascertained in many cases. Further research should address this aspect and the great potential of combining the two complementary kinds of climate paleo-archives provided by cold-water corals and contourites.
Uptake and regeneration of nitrogen in the Almeria-Oran frontal zone (SW Mediterranean) and adjacent (Atlantic and Mediterranean) systems were studied during the Almofront I cruise (JGOFS-France). The frontal zone was characterized by an upsloping of nitracline from about 50 m in the adjacent systems to 25-30 m within. Along with nitrate, ammonium, chlorophyll a and particulate organic nitrogen also were at higher concentrations in the frontal zone than in the adjacent waters. The nitrate uptake rates were significantly higher in the frontal zone (up to 6.4 nmol l(-1) h(-1)) than in the Atlantic and Mediterranean waters (generally <1 nmol l(-1) h(-1)) indicating a significant increase of new production at the front. This increase was related to the upsloping of the nitracline as shown by the significant correlation (p<0.05) between new production and depth of the nitracline. The new production in the Almeria-Oran was much lower than those recorded in other oceanic and coastal fronts. This could be related to the fact that the nitracline did not rise up to the surface and the high concentrations of nitrate were confined to deeper layers where the ambient light intensity was less. Nitrate uptake in the frontal zone was significantly higher, by 1.7-5.8 times (average 4.2), than the calculated diffusive flux of nitrate, suggesting that vertical advection may be an important source of nitrate. New production rates at the front were also significantly higher (3-9 times, average 5.8) than the PON flux to 100 m depth estimated by sediments traps (Journal of Marine Systems 5, 377-389), suggesting a strong decoupling between surface production and downward flux of POM in the frontal zone. The north-south gradient observed with different parameters indicates the presence of a transfrontal secondary circulation. This distribution also suggests that the primary production in the front is initially nitrate-based, with a diatom-herbivore food chain, whereas regenerated production, associated with an intense recycling of organic matter, later becomes progressively important in time and space.
Analysis was made of aeolo-marine dust deposits in the subtropical eastern Atlantic in order to determine the mechanisms of climatic change affecting the late Quaternary and present Saharan arid belt. Grain-size data were obtained from deep-sea samples using two approaches. The strengths of the major wind patterns that existed during the late Quaternary were quantified. The climatic changes were found to be related to the varying strength of the tropical disturbances and the varying supply of water vapour from the equatorial Atlantic. Mechanisms controlling the climate in North-west Africa during the present phase of the interglacial, were found to be more closely related to that of the last glacial than to that of the Holocene climatic optimum. (H.C.B.)
A list of 138 positions with records of Lophelia pertusa is compiled from all published and unpublished investigations in the area including material from the BIOFAR research programme. In addition, Solenosmilia variabilis, another species of branching coral new to the area is reported. The Lophelia records are from areas that are dominated by the northeastern Atlantic water (NEA W) and in depths from 200 to c. 1000 m. The highest abundance of Lophelia tends to be in the depth range where the bottom slope is critical to internal waves of semidiurnal frequency. The causal link behind this is suggested to be an increase of food availability either through higher primary production at the surface or by a redistribution of suspended particles in the bottom mixed layer.
White coral communities consist of scleractinian corals that thrive in the ocean's bathyal depths (~ 200-4000 m). In the Atlantic Ocean, white corals are known to form complex, three-dimensional structures on the seabed that attract vast amounts of other organisms, accumulate suspended detritus, and influence the local hydrodynamic flow field. These attributes coincide with what we generally describe as a coral reef. With time, environmental change causes decline of the framework-constructing corals; this is followed by erosion of the reef sequence or its draping with noncoral-related deposits. After several such sequences, the structures are known as coral carbonate mounds, which can grow as high as 350 m. Both bathyal white coral reefs and mounds are widely distributed in the Atlantic Ocean and adjacent marginal seas, such as the Gulf of Mexico. The Mediterranean Sea, however, known for its richness of fossil white coral communities exposed in land outcrops, harbors very few extant coral communities. The HERMES project extended its study sites deep into the Mediterranean with state-of-the-art mapping and visualization technology. By doing so, many previously unknown coral sites were discovered during inspections of Mediterranean narrow shelves, canyon walls, escarpments, and seamounts by remotely operated vehicles. Such shelf and continental margin settings are characteristic of the dynamic margins of the Mediterranean Sea and contrast significantly with the much broader shelves of the Atlantic Ocean. This paper reports on a HERMES cruise that was dedicated to exploring these rough submarine topographies in search of white coral communities in the central Mediterranean, and re-evaluates the general perception of the assumed paucity of white corals in this sea.
To make progress in understanding the distribution and genesis of coral mounds in cold and dark water, maps of morphology and oceanographic conditions resolving features at the 1-10 m scale are needed. An autonomous underwater vehicle (AUV) cruising 40 m above the seafloor surveyed a 48 km2 coral mound field in 600-800 m water depth at the base of slope of Great Bahama Bank. The AUV acquired 1-3 meter resolution acoustic backscatter and bathymetry together with current vectors, salinity, and temperature. The multibeam bathymetry resolved more than 200 coral mounds reaching up to 90 m height. Mound morphology is surprisingly diverse and mound distribution follows E-W oriented off-bank ridges. Bottom currents reverse every 6 hours indicating tidal flow decoupled from the north flowing surface current. The AUV data fill the gap between low-resolution surface-based mapping and visual observations on the seafloor, revealing the dynamic environment and spatial relationships of an entire coral mound field.
In a European effort (Atlantic Coral Ecosystem Study [ACES project]) to determine the key conditions for the occurrence of cold-water corals on the NW Atlantic margin, a coral community on a seamount off NW Spain (Galicia Bank) was studied. Cold-water corals (Lophelia pertusa, Madrepora oculata) grow at a depth of ∼800 m as isolated patches amidst small ripples and larger waves of foraminiferal sand. A 17 mo deployment of a near-bottom sediment trap revealed a large seasonal and annual variability in the flux of phytodetritus and carbon. The daily carbon flux in the first 5 mo of 2000 was on average 37 mgC m -2, and in the first 5 mo of 2001 17 mg C m-2. Quantities of faecal pellets and swimmers (copepods, amphipods) were also highly variable. A comparison between the daily carbon flux and the sediment carbon oxidation rate calculated from in situ community oxygen consumption (SCOC), i.e. 17 versus 7 mg C m-2 d-1 respectively, indicated that a surplus of carbon is not oxidised by the sediment community. We argue that the strong tidal currents (max. 30 cm s-1) and the mobile sediment lead to winnowing of the sediment and to near-bed transport of the organic material. The low biomass of the benthic community and the domination of filter-feeders support our arguments. By means of analyses of stable isotopes (δ15N, δ13C) we attempted to find potential food items of the cold-water corals among the particles collected in the sediment trap. The difference between the δ15N signatures of coral tissue (9.5‰) and phytodetritus (2.2‰) was >1 trophic level, indicating that sinking algae are not the sole food source. The δ15N signatures of swimmers caught in the trap, ∼10‰, were on the other hand in the same range as those of the corals. A mixed diet of animals and algae could be one explanation for the observed δ15N of corals. The δ13C value of the coral tissue, -20.55‰, excludes a food source consisting of bacteria supported by methane seepage, as suggested by earlier studies.
Sea surface temperature (SST) profiles over the last 25 kyr derived from alkenone measurements are studied in four cores from a W-E latitudinal transect encompassing the Gulf of Cadiz (Atlantic Ocean), the Alboran Sea, and the southern Tyrrhenian Sea (western Mediterranean). The results document the sensitivity of the Mediterranean region to the short climatic changes of the North Atlantic Ocean, particularly those involving the latitudinal position of the polar front. The amplitude of the SST oscillations increases toward the Tyrrhenian Sea, indicating an amplification effect of the Atlantic signal by the climatic regime of the Mediterranean region. All studied cores show a shorter cooling phase (700 years) for the Younger Dryas (YD) than that observed in the North Atlantic region (1200 years). This time diachroneity is related to an intra-YD climatic change documented in the European continent. Minor oscillations in the southward displacement of the North Atlantic polar front may also have driven this early warming in the studied area. During the Holocene a regional diachroneity propagating west to east is observed for the SST maxima, 11.5-10.2 kyr B.P. in the Gulf of Cadiz, 10-9 kyr B.P. in the Alboran Sea, and 8.9-8.4 kyr B.P. in the Thyrrenian Sea. A general cooling trend from these SST maxima to present day is observed during this stage, which is marked by short cooling oscillations with a periodicity of 730+/-40 years and its harmonics.
Studies of satellite imagery and space shuttle photographs of the western Mediterranean have indicated that the main path of inflowing Atlantic Water is around two large anticyclonic gyres in the Alboran Sea and along the Algerian Coast. These studies have also shown that a strong ocean front is present between Almeria, Spain, and Oran, Algeria, which is part of the easternmost segment of the Eastern Alboran Gyre. Based on these satellite studies, the first in situ investigation of the front, called here the Almeria-Oran Front, was conducted in March 1986 as part of the winter campaign of the Western Mediterranean Circulation Experiment (WMCE). Analyses of the resulting data show that the Almeria-Oran Front is a large-scale density front, formed by the convergence of two distinct water masses and controlled by geographic position and strength of the Eastern Alboran Gyre. Physical and biochemical data indicate that the front is limited to the upper 300 m, with a strong southward baroclinic jet. The secondary ageostrophic circulation is characterized by surface convergence, along isopycnal sinking, and upwelling on the western side of the front.
Analysis of aeolo-marine dust deposits in the subtropical eastern
Atlantic enables the strength of the major wind patterns during the late
Quaternary to be evaluated and gives an insight into the climate of
North Africa.
Growth rates of the cold-water corals (CWC) Madrepora oculata, Lophelia pertusa, Desmophyllum dianthus and Dendrophyllia cornigera were measured over 8 mo under controlled conditions (12°C in the dark, fed 5 times a week) by means of the buoyant weight technique. Addi- tionally, linear growth rates were measured in M. oculata and L. pertusa for 2 and 1 yr, respectively. The weight measurements revealed growth rates, expressed as percent growth per day (mean ± SD), of 0.11 ± 0.04 for M. oculata, 0.02 ± 0.01 for L. pertusa, 0.06 ± 0.03 for D. dianthus and 0.04 ± 0.02 % d–1 for D. cornigera. Growth in M. oculata was significantly higher (p < 0.0001) than in the other 3 CWC species. For M. oculata and L. pertusa, also linear growth was recorded. These values (mean ± SD) were 0.014 ± 0.007 and 0.024 ± 0.018 mm d–1 for M. oculata and L. pertusa, respectively. This is the first study that compares the growth rates of 4 different CWC species under the same experimen- tal conditions of water flow, temperature, salinity and food supply. These corals have different growth rates, both in terms of total weight increase and linear increase, and these growth rates can be related to interspecific physiological differences. Data on growth rates are essential to understand the popu- lation dynamics of CWC as well as the recovery capacity of these communities after disturbance.
The occurrence and density of 3 cold-water coral (CWC) species (Madrepora oculata, Lophelia pertusa and Dendrophyllia cornigera) were investigated in the Cap de Creus canyon (north- western Mediterranean) by conducting and analysing 22 video survey transects. Species distribution patterns were also investigated at 3 spatial extents (km, 100s of m and m) across 3 of the transects using spatial statistics. Additionally, the locations of snagged benthic long-line fishing gear were logged across these 3 transects. Video surveys were carried out by both remotely operated vehicles (ROVs) and the JAGO manned submersible. CWCs were present in 15 of the 22 survey transects, pre- dominantly those covering areas with hard substrate (boulders or hardrock outcrops). M. oculata was the most abundant CWC species in the survey transects, whereas L. pertusa and D. cornigera were much more sparsely distributed, with only isolated colonies observed in the majority of transects. M. oculata showed a significant contagious distribution pattern across the analysed transects, with sev- eral scales of spatial pattern and patch size being detected, whereas L. pertusa and D. cornigera were not found in sufficient numbers to apply spatial statistics. Different covariance patterns were found across the transects between snagged fishing gear and the presence of M. oculata. Further investi- gation of this relationship and the level of hazard posed by long-line fishing to M. oculata colonies is required prior to development of a protective management strategy.
By presenting sea surface temperatures, planktonic oxygen isotope profiles, and bulk geochemical composition of core sediments, we offer a multiparameter reconstruction of Western Mediterranean oceanography from the Last Glacial Maximum until the Middle Holocene (20,000-5000 cal years B. P.). Sediments from Ocean Drilling Program Site 975 in the Algero-Balearic basin have been compared with three Alboran basin cores (TTR-300G, TTR-302G, and TTR-304G), all of them investigated at high resolution. This multiproxy approach has allowed two different modes of circulation to be recognized: (1) during the LGM and from ̃8.0 cal. ka B. P. onward, no surface gradient in d18OG. bulloides is found associated with low productivity, in close analogy to modern conditions; (2) during the Bølling-Allerød and early Holocene, significant surface isotopic gradients are found with periods probably indicating an unstable water column, associated with enhanced productivity and low bottom oxygen conditions. The close synchrony between the occurrence of the surface isotopic offset and organic rich layer formation implicates that the origin of these features is linked, probably via shoaling of the regional thermohaline circulation. Paleo-SSTs, derived from planktonic foraminifer assemblages, indicate abrupt changes in surface conditions during the analyzed time interval. Fluctuations in marine productivity based on Ba and total organic carbon are related to water column stability and atmospheric conditions. A sharp warming and d18OG. bulloides excursion at the end of the Younger Dryas is probably linked to glacial meltwater influence. The riverine input has been reconstructed using the Mg/Al ratio, and Mg/Al peaks during arid periods (Greenland Stadial-2a and Younger Dryas) related to ''bypass'' margin processes.
We utilized a very dense seismic survey mainly performed by the oil companies completed by academic data to perform a depth to basement map of the Morocco margin of the Alboran Sea. The eastern area is characterized by several volcanic edifices that are related to the late Miocene Alboran arc. However, the volcanism persisted after the Messinian in the Gourougou volcano and the Chafarines Island. The Tortonian to Messinian activity of the Nekor fault system is characterized by normal faulting with a NE-SW trend. A tilt of the Messinian surface suggests a 1.5 km uplift of the coast since 5.33 Ma. In the Al Hoceima offshore region we identify the major left-lateral El Idrissi fault zone that probably crosses the Alboran Sea. The Xauen Bank is formed by the early Miocene sedimentary layers of the West Alboran Basin uplifted by compression with an estimated shortening of 3.5 km since the Messinian (0.65 mm/yr). The Jebha Fault was mainly active during the early Miocene. The tomography, the magmatism, and the tectonics suggest that the Alboran Arc collided with the Iberian Plate during the late Tortonian, followed by a clockwise rotation of the central Alboran basin. Although the Alboran basin is clearly affected by E-W motions we think that the eastwards subduction zone is dead since the late Miocene.
White coral communities consist of scleractinian corals that thrive
in the ocean’s bathyal depths (~ 200–4000 m). In the Atlantic Ocean, white corals are
known to form complex, three-dimensional structures on the seabed that attract vast
amounts of other organisms, accumulate suspended detritus, and influence the local
hydrodynamic flow field. These attributes coincide with what we generally describe
as a coral reef. With time, environmental change causes decline of the frameworkconstructing
corals; this is followed by erosion of the reef sequence or its draping
with noncoral-related deposits. After several such sequences, the structures are
known as coral carbonate mounds, which can grow as high as 350 m. Both bathyal
white coral reefs and mounds are widely distributed in the Atlantic Ocean and
adjacent marginal seas, such as the Gulf of Mexico. The Mediterranean Sea, however,
known for its richness of fossil white coral communities exposed in land outcrops,
harbors very few extant coral communities. The HERMES project extended its study
sites deep into the Mediterranean with state-of-the-art mapping and visualization
technology. By doing so, many previously unknown coral sites were discovered
during inspections of Mediterranean narrow shelves, canyon walls, escarpments,
and seamounts by remotely operated vehicles. Such shelf and continental margin
settings are characteristic of the dynamic margins of the Mediterranean Sea and
contrast significantly with the much broader shelves of the Atlantic Ocean. This paper
reports on a HERMES cruise that was dedicated to exploring these rough submarine
topographies in search of white coral communities in the central Mediterranean, and
re-evaluates the general perception of the assumed paucity of white corals in this sea.
Past sea surface temperature (SST) evolution in the Alboran Sea (western Mediterranean) during the last 50,000 years has been inferred from the study of C37 alkenones in International Marine Global Change Studies MD952043 core. This record has a time resolution of ~200 years allowing the study of millennial-scale and even shorter climatic changes. The observed SST curve displays characteristic sequences of extremely rapid warming and cooling events along the glacial period. Comparison of this Alboran record with δ18O from Greenland ice (Greenland Ice Sheet Project 2 core) shows a strong parallelism between these SST oscillations and the Dansgaard-Oeschger events. Five prominent cooling episodes standing out in the SST profile are accompanied by an anomalous high abundance of Neogloboquadrina pachyderma sinistral which is confined to the duration of these cold intervals. These features and the isotopic record reflect drastic changes in the surface hydrography of the Alboran Sea in association with Heinrich events H1-5.
Sr isotope stratigraphy provides a new age model for the first complete section drilled through a deep-water coral mound. The 155-m-long section from Challenger Mound in the Porcupine Sea-bight, southwest of Ireland, is on Miocene siliciclastics and consists entirely of sediments bearing well-preserved cold-water coral Lophelia pertusa. The 87Sr/86Sr values of 28 coral specimens from the mound show an upward-increasing trend, correspond to ages from 2.6 to 0.5 Ma, and identify a significant hiatus from ca. 1.7 to 1.0 Ma at 23.6 m below seafloor. The age of the basal mound sediments coincides with the intensification of Northern Hemisphere glaciations that set up the modern stratification of the northeast Atlantic and enabled coral growth. Mound growth persisted throughout glacial-interglacial fluctuations, reached a maximum rate (24 cm/k.y.) ca. 2.0 Ma, and ceased at 1.7 Ma. Unlike other buried mounds in Porcupine Seabight, Challenger Mound was only partly covered during its growth interruption, and growth restarted ca. 1.0 Ma.
Cold-water coral carbonate mounds, owing their presence mainly to the framework building coral Lophelia pertusa and the activity of associated organisms, are common along the European margin with their spatial distribution allowing them to be divided into a number of mound provinces. Variation in mound attributes are explored via a series of case studies on mound provinces that have been the most intensely investigated: Belgica, Hovland, Pelagia, Logachev and Norwegian Mounds. Morphological variation between mound provinces is discussed under the premise that mound morphology is an expression of the environmental conditions under which mounds are initiated and grow. Cold-water coral carbonate mounds can be divided into those exhibiting “inherited” morphologies (where mound morphology reflects the morphology of the colonised features) and “developed” morphology (where the mounds assume their own gross morphology mainly reflecting dominant hydrodynamic controls). Finer-scale, surface morphological features mainly reflecting biological growth forms are also discussed.
We reviewed the factors influencing organic carbon and carbonate preservation in marine sediments. The application and problems of these two biogenic components as paleoproductivity proxies are exemplified by comparison of two sediment cores: one from the high productivity upwelling region off Angola, and the other from the low productivity area off North Brazil. Unlike the upwelling site, sedimentary organic carbon in the low productivity area is problematic as a paleoproductivity indicator. There, calcium carbonate, the predominant biogenic material of the pelagic ocean, serves as an alternative estimator for paleoproductivity. During the last 300,000 years, high and variable paleoproductivity in the eastern Atlantic contrasts with low and relatively constant values in the West. Beyond this, a countercyclicity of paleoproductivity variations between the eastern and the western tropical Atlantic is observed. During cold climatic substages, paleoproductivity was at maximum in the East, whereas minimum values were recorded in the West. These inverse relationships are attributed to a lowered nutrient concentration of glacial intermediate waters which are the nutrient source of open ocean new production. At the same time, the supply of nutrients was enhanced in the eastern Atlantic due to intensified wind-driven upwelling. Moreover, the increased zonal wind stress may have caused a deepening of the nutricline in the West coupled with a synchronous shallowing in the East. The sharp Glacial-to-Holocene decrease in paleoproductivity in the upwelling areas (dominated by opal producers), occurred contemporaneously with an increase in the oligotrophic open ocean (dominated by carbonate producers). This should have resulted in a decrease of the carbon rain ratio (Corg /CCaCO3), possibly contributing to the observed Glacial-to-Holocene increase in atmospheric pCO2
Sr isotope stratigraphy provides a new age model for the first complete section drilled through a deep-water coral mound. The 155-m-long section from Challenger Mound in the Porcupine Sea-bight, southwest of Ireland, is on Miocene siliciclastics and consists entirely of sediments bearing well-preserved cold-water coral Lophelia pertusa. The ⁸⁷Sr/⁸⁶Sr values of 28 coral specimens from the mound show an upward-increasing trend, correspond to ages from 2.6 to 0.5 Ma, and identify a significant hiatus from ca. 1.7 to 1.0 Ma at 23.6 m below seafloor. The age of the basal mound sediments coincides with the intensification of Northern Hemisphere glaciations that set up the modern stratification of the northeast Atlantic and enabled coral growth. Mound growth persisted throughout glacial-interglacial fluctuations, reached a maximum rate (24 cm/k.y.) ca. 2.0 Ma, and ceased at 1.7 Ma. Unlike other buried mounds in Porcupine Seabight, Challenger Mound was only partly covered during its growth interruption, and growth restarted ca. 1.0 Ma.
Elongated carbonate mounds ("lithoherms") oriented parallel to prevailing northerly bottom currents at moderate depths (500-700 m) along the western margin of the Little Bahama Bank exhibit a consistent faunal zonation characterized by attached, suspension-feeding invertebrates. The four most abundant macroepibenthic groups (alcyonarians, crinoids, sponges and stylasterid hydrocorals) dominate all hard substrates examined except upcurrent ends and crests of lithoherms. We recognize three faunal zones on these mounds: a Coral Zone (Lophelia prolifera) restricted to the upcurrent end; a Zoanthid Zone (?Gerardia sp.) along upcurrent crests, and a Crinoid/Alcyonarian Zone along lithoherm flanks and downstream crests. Taxa characteristic of the latter also occur on surrounding, low-relief hardgrounds but are accompanied by additional taxa usually absent from mounds. Intervening unconsolidated sediment is largely barren. Biozonation appears chiefly dependent on current flow regime and secondarily on substrate. The observed zonation occurs over a much smaller areal scale than previously reported for deep-water (non-hydro-thermal) hard bottoms. Abrupt, small-scale faunal zonation can no longer automatically be considered as evidence of a shallow-water environment in interpreting fossil assemblages.
Uptake and regeneration of nitrogen in the Almeria-Oran frontal zone (SW Mediterranean) and adjacent (Atlantic and Mediterranean) systems were studied during the Almofront I cruise (JGOFS-France). The frontal zone was characterized by an upsloping of nitracline from about 50 m in the adjacent systems to 25–30 m within. Along with nitrate, ammonium, chlorophyll a and particulate organic nitrogen also were at higher concentrations in the frontal zone than in the adjacent waters.The nitrate uptake rates were significantly higher in the frontal zone (up to 6.4 nmol l−1 h−1) than in the Atlantic and Mediterranean waters (generally <1 nmol l−1 h−1) indicating a significant increase of new production at the front. This increase was related to the upsloping of the nitracline as shown by the significant correlation (p<0.05) between new production and depth of the nitracline. The new production in the Almeria-Oran was much lower than those recorded in other oceanic and coastal fronts. This could be related to the fact that the nitracline did not rise up to the surface and the high concentrations of nitrate were confined to deeper layers where the ambient light intensity was less. Nitrate uptake in the frontal zone was significantly higher, by 1.7–5.8 times (average 4.2), than the calculated diffusive flux of nitrate, suggesting that vertical advection may be an important source of nitrate. New production rates at the front were also significantly higher (3–9 times, average 5.8) than the PON flux to 100 m depth estimated by sediments traps (Journal of Marine Systems 5, 377–389), suggesting a strong decoupling between surface production and downward flux of POM in the frontal zone.The north–south gradient observed with different parameters indicates the presence of a transfrontal secondary circulation. This distribution also suggests that the primary production in the front is initially nitrate-based, with a diatom-herbivore food chain, whereas regenerated production, associated with an intense recycling of organic matter, later becomes progressively important in time and space.
An extensive dataset collected in the Alboran Sea during the 1982 Donde Va experiment is used to characterize the kinematics and dynamics of the inflow of Atlantic water into the Mediterranean Sea. The veering of the inflow toward the ENE after leaving the Strait of Gibraltar and the existence of an anticyclonic gyre that fills much of the western Alboran Sea in the upper 200 m are confirmed in the mean. Inflow variability with periods of 2 to 10 days is described. Particularly striking is one interval of about nine days during which the gyre was not present and the inflow adopted a southerly course after leaving the strait. The observations are interpreted in terms of vorticity conservation and in the light of earlier theoretical and numerical results. (A)
This paper provides an introduction to the following 12 papers of this special issue of the journal. In addition to a brief historical review and a description of the Almeria-Oran front (Eastern Alboran Sea), a summary is given here of the “Almofront-1” cruise as regards objectives, strategies and methods. The main physical, chemical and biological features of the front as encountered during the “Almofront-1” cruise are presented, illustrated and discussed.
Based on the glacial to postglacial δ13C differences
between endobenthic Uvigerina peregrina species from the Alboran basin
and from other mediterranean basins, changes in the fertility of the
western part of this basin during the last deglaciation are
reconstructed. As a result of particulate organic carbon (POC) rain from
the highly productive upwelling cell along the northwestern margin of
the Alboran basin, U. peregrina is presently depleted by about
1.6‰ with respect to the measured δ13C values of
bottom water ΣCO2 and by about 0.9‰ with respect
to specimens from other areas of the western Mediterranean or from the
Gulf of Cadiz within the Mediterranean Outflow Water. The Uvigerina
δ13C difference between the Alboran Sea and the Gulf of
Cadiz (Δδ13C), was close to 0‰ at the
beginning of the last deglaciation and during the late glacial time.
This suggests that highly fertile systems set in the Alboran Sea near 16
kyr B.P. Two rapid increases in the Δδ13C offset
are recorded near 15 kyr and 11 kyr B.P. Fluctuations around 1.1 to
1.2‰ occurred during the early Holocene, and a maximum was
reached near 9 kyr B.P. After 4 kyr the Δ δ13C
offset decreased to its present-day average value of 0.9‰.
Changes in the intensity of surficial production cannot account for all
the observed fluctuations, especially in the early Holocene time. A
strong decrease in the intermediate and deep water ventilation of the
Alboran basin may have occurred near 8-9 kyr, in phase with the last
stagnant phase in the eastern Mediterranean and the deposition of
Sapropel S1. As a result, the redistribution and remineralization at
depth of the produced organic matter was incomplete. The POC rain
reaching the sediment was locally intensified and caused the lowering of
the δ13C values of endobenthic foraminifers such as U.
peregrina. The benthic 13C signal suggests that the
difference between the Alboran Sea and the Gulf of Cadiz was at its
maximum. At the same time, an important modification in the water masses
structure may have occurred near 9-8 kyr B.P. The deepening of the
permanent pycnocline probably related to a thicker Atlantic jet at a
stage of high sea level stand is recorded by the replacement of the
right coiling N. pachyderma dominance (coincident with a shallow
pycnocline) by the G. inflata dominance (coincident with a deep
pycnocline). Diatom abundances were strongly reduced indicating an
important modification of the productive system. The glacial-postglacial
evolution of productivity within the Alboran basin was therefore more
complex than in the adjacent Atlantic Ocean and opposite to the global
one which displays a general increase in productivity during glacial
time. Although it is the global budget of paleoproductivity that would
drive the partitioning of carbon within the ocean, local or regional
discrepancies with the global glacial-interglacial model must be
addressed. Local winds and regional atmospheric pressure systems, which
are the forcing factors for circulation and exchange with the Atlantic,
control the fertile systems of the Alboran basin.
The IMAGES core MD99-2343, recovered from a sediment drift north of the island of Minorca, in the north-western Mediterranean Sea, holds a high-resolution sequence that is perfectly suited to study the oscillations of the overturning system of the Western Mediterranean Deep Water (WMDW). Detailed analysis of grain-size and bulk geochemical composition reveals the sensitivity of this region to climate changes at both orbital and centennial–millennial temporal scales during the last 50 kyr. The dominant orbital pattern in the K/Al record indicates that sediment supply to the basin was controlled by the insolation evolution at 40°N, which forced changes in the fluvial regime, with more efficient sediment transport during insolation maxima. This orbital control also modulated the long-term pattern of the WMDW intensity as illustrated by the silt/clay ratio.
Historical satellite, aircraft, and in situ data have shown that two anticyclonic gyres (the western and eastern Alboran gyres) are major ocean features of the Alboran Sea. An examination of several years of satellite imagery indicates that large variations in the surface expression of these two gyres occur and that on occasion one or the other gyre disappears (the disappearance of both gyres at the same time was not seen). The initial disappearance of either gyre occurs on a time scale of a week to 2 weeks, whereas the return may take from 3 weeks to 2 months. Various forcing mechanisms, i.e., winds, mass flux inflow through the Straits of Gibraltar and Sicily, and/or density, have been used in numerical ocean circulation models to study the dynamics of the western Mediterranean Sea. Various model results show relationships similar to those shown by the satellite imagery. However, no single forcing mechanism has been positively identified as the source of the disappearances, and the events may be a result of a combination of forcing mechanisms. Keywords: Nowcasting; Ocean circulation/models; Mathematical models; Reprints.
Continuous sedimentary records from an eastern Mediterranean cold-water coral ecosystem thriving in intermediate water depths ($ 600 m) reveal a temporary extinction of cold-water corals during the Early to Mid Holocene from 11.4–5.9 cal kyr BP. Benthic foraminiferal assemblage analysis shows low-oxygen conditions of 2 ml l À 1 during the same period, compared to bottom-water oxygen values of 4–5 ml l À 1 before and after the coral-free interval. The timing of the corals' demise coincides with the sapropel S1 event, during which the deep eastern Mediterranean basin turned anoxic. Our results show that during the sapropel S1 event low oxygen conditions extended to the rather shallow depths of our study site in the Ionian Sea and caused the cold-water corals temporary extinction. This first evidence for the sensitivity of cold-water corals to low oceanic oxygen contents suggests that the projected expansion of tropical oxygen minimum zones resulting from global change will threaten cold-water coral ecosystems in low latitudes in the same way that ocean acidification will do in the higher latitudes.
This paper presents the first compilation of information on the spatial distribution of scleractinian cold-water corals in the Gulf of Cádiz based on literature research and own observations (video footage, sediment samples). Scleractinian cold-water corals are widely distributed along the Spanish and Moroccan margins in the Gulf of Cádiz, where they are mainly associated with mud volcanoes, diapiric ridges, steep fault escarpments, and coral mounds. Dendrophyllia cornigera, Dendrophyllia alternata, Eguchipsammia cornucopia, Madrepora oculata and Lophelia pertusa are the most abundant reef-forming species. Today, they are almost solely present as isolated patches of fossil coral and coral rubble. The absence of living scleractinian corals is likely related to a reduced food supply caused by low productivity and diminished tidal effects. In contrast, during the past 48 kyr scleractinian corals were abundant in the Gulf of Cádiz, although their occurrence demonstrates no relationship with main climatic or oceanographic changes. Nevertheless, there exists a conspicuous relationship when the main species are considered separately. Dendrophylliids are associated with periods of relatively stable and warm conditions. The occurrence of L. pertusa mainly clusters within the last glacial when bottom current strength in the Gulf of Cádiz was enhanced and long-term stable conditions existed in terms of temperature. Madrepora oculata shows a higher tolerance to abrupt environmental changes.
Knolls are prominent features in the Alboran Sea, Western Mediterranean. Multibeam bathymetry and backscatter data, combined with TOPAS parameteric profiles, surficial sediment sampling, and video transects for ground-truthing revealed a large relict cold-water coral habitat. This habitat consists mainly of dead and living Dendrophyllia sp. and, to a lesser extent, Lophelia pertusa and Madrepora occulata associated with giant deep-sea oysters Neopycnodonte zibrowii sp., and gorgonians. The knolls display flat shoaling tops ranging from 70 m (Chella Bank) down to 430 m (La Herradura knoll) depth and rise ~400–600 m above the surrounding seafloor. Sediment cover on the knolls is in general thin and mainly consists of bioclastic coarse sandy sediment. The slope of knoll flanks is up to 70°, with stepped ridges and near-vertical walls colonized with corals. At the summit of the knolls, cold-water corals are observed.
a b s t r a c t This paper presents the first compilation of information on the spatial distribution of scleractinian cold-water corals in the Gulf of Cá diz based on literature research and own observations (video footage, sediment samples). Scleractinian cold-water corals are widely distributed along the Spanish and Moroccan margins in the Gulf of Cá diz, where they are mainly associated with mud volcanoes, diapiric ridges, steep fault escarpments, and coral mounds. Dendrophyllia cornigera, Dendrophyllia alternata, Eguchipsammia cornucopia, Madrepora oculata and Lophelia pertusa are the most abundant reef-forming species. Today, they are almost solely present as isolated patches of fossil coral and coral rubble. The absence of living scleractinian corals is likely related to a reduced food supply caused by low productivity and diminished tidal effects. In contrast, during the past 48 kyr scleractinian corals were abundant in the Gulf of Cá diz, although their occurrence demonstrates no relationship with main climatic or oceanographic changes. Nevertheless, there exists a conspicuous relationship when the main species are considered separately. Dendrophylliids are associated with periods of relatively stable and warm conditions. The occurrence of L. pertusa mainly clusters within the last glacial when bottom current strength in the Gulf of Cá diz was enhanced and long-term stable conditions existed in terms of temperature. Madrepora oculata shows a higher tolerance to abrupt environmental changes.
A set of 40 Uranium-series datings obtained on the reef-forming scleractinian cold-water corals Lophelia pertusa and Madrepora oculata revealed that during the past 400 kyr their occurrence in the Gulf of Cádiz (GoC) was almost exclusively restricted to glacial periods. This result strengthens the outcomes of former studies that coral growth in the temperate NE Atlantic encompassing the French, Iberian and Moroccan margins dominated during glacial periods, whereas in the higher latitudes (Irish and Norwegian margins) extended coral growth prevailed during interglacial periods. Thus it appears that the biogeographical limits for sustained cold-water coral growth along the NE Atlantic margin are strongly related to climate change. By focussing on the last glacial–interglacial cycle, this study shows that palaeo-productivity was increased during the last glacial. This was likely driven by the fertilisation effect of an increased input of aeolian dust and locally intensified upwelling. After the Younger Dryas cold event, the input of aeolian dust and productivity significantly decreased concurrent with an increase in water temperatures in the GoC. This primarily resulted in reduced food availability and caused a widespread demise of the formerly thriving coral ecosystems. Moreover, these climate induced changes most likely caused a latitudinal shift of areas with optimum coral growth conditions towards the northern NE Atlantic where more suitable environmental conditions established with the onset of the Holocene.
Cold-water corals are widely distributed along the Atlantic continental margin with varying growth patterns in relation to their specific environment. Here, we investigate the long-term development of cold-water corals that once thrived on a low-latitude (17°40′N) cold-water coral mound in the Banda Mound Province off Mauritania during the last glacial–interglacial cycle. U/Th dates obtained from 20 specimens of the cold-water coral Lophelia pertusa, revealed three distinct periods of coral growth during the last glacial at 65 to 57 kyr BP, 45 to 32 kyr BP and 14 kyr BP, thus comprising the cool periods of Marine Isotopic Stages (MIS) 2–4. These coral growth periods occur during periods of increased productivity in the region, emphasizing that productivity seems to be the major steering factor for coral growth off Mauritania, which is one of the major upwelling regions in the world. This pattern differs from the well studied coral mounds off Ireland, where the current regime predominantly influences the prosperity of the cold-water corals. Moreover, coral growth off Ireland takes place during rather warm interglacial and interstadial periods, whereas off Mauritania coral growth is restricted to glacial and stadial periods. However, the on-mound sedimentation patterns off Mauritania largely resemble the observations reported from the Irish mounds. The bulk of the preserved sediments derives from periods of coral growth, whereas during periods without corals hardly any net sedimentation or mound growth took place.
The first detailed stratigraphic record from a deep-water carbonate mound in the Northeast Atlantic based on absolute datings (U/Th and AMS 14 C) and stable oxygen isotope records reveals that its top sediment sequences are condensed by numerous hiatuses. According to stable isotope data, mainly sediments with an intermediate signal are preserved on the mound, while almost all fully glacial and interglacial sediments have either not been deposited or have been eroded later. The resulting hiatuses reduce the Late Pleistocene sediment accumulation at Propeller Mound to amounts smaller than the background sedimentation. The hiatuses most likely result due to the sweeping of the mound in turn with the re-establishment of vigour interglacial circulation patterns after sluggish current regimes during glacials. Thus, within the discussion if internal, fluid-driven or external environmentally driven processes control the evolution of such carbonate mounds, our findings for Propeller Mound clearly 0012-821X/$ -see front matter D 2005 Elsevier B.V. All rights reserved.
Hydrographic and current meter data, obtained during June to October 1982, and numerical model experiments are used to study the distribution and flow of Mediterranean waters in the western Alboran Sea. The Intermediate Water is more pronounced in the northern three-fourths of the sea, but its distribution is patchy as manifested by variability of the temperature and salinity maxima at scales ≤10 km. Current meters in the lower Intermediate Water showed mean flow toward the Strait at 2 cm s−1. A reversal of this flow lasted about 2 weeks. A rough estimate of the mean westward Intermediate Water transport was 0.4 × 106 m3 s–1, about one-third of the total outflow, so that the best estimates of the contributions of traditionally defined Intermediate Water and Deep Water account for only about one-half of the total outflow. The Deep Water was uplifted against the southern continental slope from Alboran Island (3°W) to the Strait. There was also a similar but much weaker banking against the Spanish slope, but a deep current record showed that the eastward recirculation implied by this banking is probably intermittent. Two-layer numerical model experiments simulated the Intermediate Water flow with a flat bottom and the Deep Water with realistic bottom topography. Both experiments replicated the major circulation features, and the Intermediate Water flow was concentrated in the north because of rotation and the Deep Water flow in the south because of topographic control.
Sapropels, which are dark sediments with organic carbon content >2 wt%, are common in eastern Mediterranean sections. In some western Mediterranean sites, however, even organic-rich layers (ORLs) are not detected in sections spanning the S1 sapropel deposition event (9500–6000 yr BP). We compare geochemical and mineralogical compositions in cores from the eastern (Ionian Sea) and western (Alboran Sea and South Balearic basin) Mediterranean basins to determine the causes for the lack of ORL deposition during S1 in the western basin. In particular, we investigate whether the differences between the eastern and western sites are due to preservation or productivity variations. Using mineralogical and geochemical data – mineral abundances, major and trace element concentrations and ratios, organic carbon content, Ba and barite accumulations, and sea surface temperature data – along with information about the sedimentary regimes, sedimentation rates, and water depths at these sites, we conclude that the lack of S1 sapropel formation in the western Mediterranean is due to lower export production fluxes in this basin. Accordingly, the response to regional climate changes through time must be different in the eastern and western Mediterranean. Identifying the exact causes for these differences may lead to an understanding of the variations in export production rates in response to basin-wide versus regional climate changes in the Mediterranean region.
Cold-water coral carbonate mound development is the result of complex and interactive hydrographical, biological and geological processes that can result in morphostructures several hundred meters high. The case study presented here investigates one of these large mounds – Galway Mound – in the eastern Porcupine Seabight to build an understanding of mound forming processes and the driving factors. For the first time, bottom current data have been recorded at six locations over a mound thus allowing an interpretation of the local flow field to be made. In addition to the overall flow pattern in the Porcupine Seabight, the recorded data display distinct diurnal tides. Comparison of the local flow field, coral facies distributions, current induced seabed features and grain size distributions over the Galway Mound highlights a correlation between the abundance of living corals with areas of enhanced bottom currents. However, the interplay of contour currents, tidal currents and the local topography further influences the coral facies and results in a distinct asymmetry in the coral facies distribution at Galway Mound. By baffling sediment, the corals also affect sedimentation on the mound.
The Dhaka and Maya mud volcanoes (MVs), located in the Mud Diapir Province in the Western Alboran Basin along the Moroccan Coasts, were cored during the TTR-17, Leg 1 cruise. Cores were taken on the top of the volcanoes at a water depth of 370 m on the Dhaka MV (core TTR17-MS411G) and at 410 m water depth on the Maya MV (core TTR17-MS419G), respectively. On both mud volcanoes the extruded mud breccia provides the nucleation point for the colonization and development of cold-water corals and associated ecosystems. Two phases of cold-water coral growth are observed: (1) between slightly older than 4175± 62 years BP and around 2230± 59 years BP at Dhaka, and (2) between slightly older than 15583 ± 185 years BP and around 7613 ± 38 years BP at Maya MV. On the top of the Maya MV only a small patch reef and/or isolated corals proliferated, whereas a more extended patch reef colonized the top of the Dhaka MV. At both sites the cold-water coral development was triggered by the availability of a suitable substrate for initial coral settling, provided either as a firm ground or as single clasts. Subsequently coral growth was supported by enhanced nutrient flux possibly related to upwelling and/or strong currents. During the intervals of coral growth planktonic foraminiferal assemblages were dominated by Neogloboquadrina incompta. The decline of coral ecosystems on the mud volcanoes is accompanied at surface by a shift from the N. incompta dominated assemblage to a Globorotalia inflata dominated assemblage, possibly reflecting more oligotrophic conditions. This shift is coeval to the passage from wet to arid conditions at the end of the African Humid Period at Maya MV. It is interpreted as an effect of an early human impact on a fragile environment, which was already stressed by desiccation at the time of the development of complex human society along the Mediterranean coasts, at Dhaka MV.
Uranium-series and radiocarbon ages are reported for deep-sea corals Madrepora oculata, Desmophyllum dianthus, Lophelia pertusa and Caryophyllia smithii from the Mediterranean Sea. U-series dating indicates that deep-sea corals have persisted in the Mediterranean for over 480,000 years, especially during cool interstadial periods. The most prolific period of growth however appears to have occurred within the Younger Dryas (YD) period from 12,900 to 11,700 years BP followed by a short (~ 330 years) phase of post-YD coral growth from 11,230 to 10,900 years BP. This indicates that deep-sea corals were prolific in the Mediterranean not only during the return to the more glacial-like conditions of the YD, but also following the rapid deglaciation and transition to warmer conditions that followed the end of the YD. Surprisingly, there is a paucity Last Glacial Maximum (LGM) coral ages, implying they were largely absent during this period when cold-water conditions were more prevalent. Radiocarbon ages show that the intermediate depth waters of the Mediterranean generally had Δ14C compositions similar to surface waters, indicating that these waters were extremely well ventilated. The only exception is a narrow period in the YD (12,500 ± 100 years BP) when several samples of Lophelia pertusa from the Ionian Sea had Δ14C values falling significantly below the marine curve. Using a refined approach, isolation ages (τisol) of 300 years to 500 years are estimated for these intermediate (800–1000 m) depth waters relative to surface marine waters, indicating a reduction or absence of deep-water formation in the Ionian and adjacent Adriatic Seas during the YD. Contrary to previous findings, we find no evidence for widespread intrusion of low Δ14C Atlantic waters into the Mediterranean. Prolific growth of deep-sea corals in the Mediterranean ended abruptly at ~ 10,900 years BP, with many of the coral-bearing mounds on the continental slopes being draped in a thin veneer of mud. Their demise is attributed to a number of factors, including the direct loss of habitat due to high sedimentation that accompanied glacial meltwater pulses, together with rising temperatures that would have finally pervaded the deeper water of the Mediterranean following the onset of Holocene warming.
Continuous sedimentary records from an eastern Mediterranean cold-water coral
ecosystem thriving in intermediate water depths (∼ 600 m) reveal a temporary extinction of
Continuous sedimentary records from an eastern Mediterranean cold-water coral
ecosystem thriving in intermediate water depths (∼ 600 m) reveal a temporary extinction of
cold-water corals during the Early to Mid Holocene from 11.4–5.9 cal kyr BP. Benthic
foraminiferal assemblage analysis shows low-oxygen conditions of 2 ml l− 1 during the
same period, compared to bottom-water oxygen values of 4–5 ml l− 1 before and after the
coral-free interval. The timing of the corals' demise coincides with the sapropel S1 event,
Detailed analysis of the planktonic foraminifera assemblages of ODP Site 977, situated in the Alboran Sea (36°1,9′N; 1°57,3′W), led us to recognize 42 planktonic foraminiferal events that occurred during marine isotope stages (MIS) 4 and 5. These events were defined by changes in the abundances of Neogloboquadrina pachyderma (right and left coiling), Turborotalita quinqueloba, Globorotalia scitula, Globorotalia inflata, Globigerina bulloides and Globigerinoides ruber (white and pink varieties). Foraminiferal assemblages changed in response to glacial-interglacial and millennial climate variability throughout the last 150 ka. Based on the estimation of sea surface temperatures (SST) using the modern analog technique and the oxygen isotope data measured in G. bulloides, we inferred the oxygen isotopic composition of sea water (δw). SST increased in the Alboran Sea during the main Dansgaard-Oeschger Interstadials, such as interstadial 19 to 24. Even though N. pachyderma (left coiling) is very scarce before Heinrich Event (HE) 6, three cold pulses can be identified, between 65 and 85 ka ago. Moreover, increases in abundance of T. quinqueloba and G. scitula are recorded during D-O Stadials 20 and 21. The maximum temperature, which was attained during the Last Interglacial, was about 2°C higher than recent temperature and that reached over the Holocene. Planktic foraminifera assemblages and paleotemperatures remained cold 3 ka after the beginning of Termination II (T-II), 130 ka ago, probably in connection with the occurrence of Heinrich event 11 in the North Atlantic. The abundance of G. bulloides during the deposition of organic rich layers (ORLs) of MIS 5, accompanied by lower isotope values in surface waters (δw), could indicate the presence of a fresher surface layer associated with an increase in marine surface productivity.