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Baseline benthic foraminiferal assemblages and habitat conditions in a sub-Arctic region of increasing petroleum development
Abstract
The aim of this study is to establish pre-impact baseline conditions for an Arctic region where petroleum activities are projected to increase in the coming decades. We characterize the spatial distribution of living benthic foraminifera in the Tromsøflaket-Ingøydjupet region of the Barents Sea and relate this to sediment properties and their associated metal concentrations. Metal concentrations of the sediments did not exceed threshold levels of harmful environmental effects, indicating that the area exhibits pre-impact baseline conditions. Foraminiferal assemblages reflect the pristine environment. Epifaunal species dominate in Tromsøflaket, a high energy environment characterized by coarse grained sediments. Infaunal species dominate in Ingøydjupet, a low energy environment characterized by fine grained sediments. Metal concentrations were slightly elevated in the fine grained sediments from Ingøydjupet which suggest that these areas may in the future serve as trapping zones for contaminants associated with discharges from nearby petroleum sites.
... − 20°C) (Table 1) (e.g. Dijkstra et al., 2013). The frozen cores were X-rayed using a Geotek X-ray core imaging system at the Arctic University of Norway in Tromsø (UiT) geological laboratory ( Fig. 1D; Table 1). ...
... Benthic calcareous and planktic foraminifera were picked and identified to species level, while agglutinated benthic forms were identified to genus level. Foraminifera were picked in sediment splits of the 100 μm-1 mm size fraction to enable comparison to studies from the region (Hald and Steinsund, 1992;Knudsen, 1998;Polyak et al., 2002;Sejrup et al., 2004;Saher et al., 2009Saher et al., , 2012Dijkstra et al., 2013Dijkstra et al., , 2015. From most samples a specimen number of ca. ...
... Elevated heavy metal values, linked to drilling operations and oil production, have been observed at and in the vicinity of drill cutting piles and platforms in the North Sea (Breuer et al., 2004 and ref. therein). However, in the present study most heavy metal concentrations (Hg, Cd, Cr, Cu, Pb, Zn, Ti), at all distances from the drill hole, are comparable to background levels as classified by the Norwegian Pollution Control Authority (Bakke et al., 2007(Bakke et al., , 2010 and documented in local non-impacted areas (Dijkstra et al., 2013(Dijkstra et al., , 2015 (Fig. 3). Elevated sediment Ba levels are common at and near drill cutting piles and are linked to Barite often used and release during drilling procedures (Breuer et al., 2004 and ref. therein;Neff, 2005). ...
The present multiproxy investigation of marine sediment cores aims at: 1) Identifying dispersion of petroleum exploration related drill cutting releases within the Goliat Field, Barents Sea in 2006/07 and 2) Assessing past and present influence of drill cuttings on the marine environment. The cores were recovered 5, 30, 60, 125 and 250 m from the drill site in the eastward downstream direction.
Downstream dispersion of drill cuttings is evaluated by examining sediment grain size distribution and barium (Ba), heavy metal, total organic carbon and sulphur concentrations. Dispersion of drill cuttings was limited to < 125 m east from the drill site. Influence of drill cutting releases on the marine environment is assessed via microfaunal analysis of primarily calcareous benthic foraminifera. The findings suggest contemporaneous physical smothering at ≤ 30 m from the drill site, with a natural fauna reestablishing after drilling cessation indicating no long-term effect of drill cutting releases.
... In general, coarse-grained sediments are observed in shallow depths due to strong bottom currents. Finer material deposits are observed at greater depths due to weak ocean currents (Bellec et al., 2008 and references therein; Dijkstra et al., 2013;Junttila et al., 2014). ...
... Petroleum exploration well (EW) sites and the Goliat and Snøhvit oil and gas fields (OGF) are indicated by stars. Dijkstra et al., 2013). In addition, 7 samples were collected in the summer of 2010 (Statoil set). ...
... All of the samples were analyzed for grain size, TOC, PAH compounds, and 210 Pb dating (for sediment age determinations).The grain-size and TOC data for the surface samples have been previously published in Dijkstra et al. (2013) and the grain size, TOC data, and 210 Pb dating for the sediments cores have been previously published in Junttila et al. (2014). The PAH compositions for the Statoil set have been previously published in Mannvik et al. (2011). ...
The concentration and distribution of polyaromatic hydrocarbons (PAHs) in surface and subsurface sediment samples from Tromsoflaket and Ingoydjupet, southwestern Barents Sea, were investigated in order to provide insight into the levels and origins of PAHs in a region with petroleum activities. PAH profiles in sediments were evaluated in context with sediment grain size and total organic carbon in order to assess the influence of ocean currents on the transportation and deposition of PAHs. The PAH concentrations are of background (Level I) to good level (Level II) based on the Water Framework Directive classification system. SUM PAH (SUM of 26 PAH compounds) ranged from 39 to 2197 μg/kg (average 225 μg/kg), and NPD (naphthalene, phenanthrene and dibenzothiophene, including their C1-C3 alkyl homologues) in surface samples ranged from 14 to 2045 μg/kg (average 157 μg/kg). However, the average values presented here are higher than have been reported in previous studies. The observed changes in PAH contents in surface and subsurface sediments vary in accordance with changes in grain size (clay and silt 17-99%) and total organic carbon content (0.37-0.98%). In turn, these sedimentary parameters are controlled by the inflow of Atlantic Water and the strength of the two predominating current systems in this region: the North Atlantic Current and Norwegian Coastal Current. Source-allocation modeling suggests that PAHs in surface samples are mainly of pyrogenic or mixed pyrogenic and petrogenic origin. Taken together, these patterns of PAH levels and sources reflect natural variability, indicating that the derived dataset establishes a pre-impacted baseline of the present state of the seafloor.
... temperature and available nutrition (e.g. Saher et al., 2012;Dijkstra et al., 2013). Studies that compare the living and dead benthic foraminiferal assemblages point to some preservation issues (transport, bioturbation, dissolution and/or broken test), which may bias the interpretation of the fossil record (e.g., Hald and Korsun, 1997;Wollenburg and Mackensen, 1998;Dijkstra et al., 2017a;Dijkstra et al., 2017b). ...
... 100 years. In contrast to other studies from other areas of the Barents Sea that indicate a larger and progressively increasing influence of the Atlantic water either within the last 200 years (Wilson et al., 2011;Dijkstra et al., 2013) or with the last ca. 30 years (Saher et al., 2012). ...
We examine the living and dead benthic foraminiferal assemblages from the topmost 10 cm (using 150 μm sieve fraction) of three sedimentological short records collected in the Kveithola Trough (northwest Barents Sea). Our aim is to reconstruct the environmental variations of the last decades, connected to the interaction among the North Atlantic and the Arctic water masses. Our samples are collected at water depths between 150 and 380 m during the Eurofleets2-BURSTER oceanographic cruise, on board of the R/V Polarstern (June 2016).
In the Cell Tracker Green (CTG) labelled living foraminiferal fauna, the main species are Pullenia bulloides, Globobulimina auriculata, and Nonionellina labradorica, while in the dead assemblages the main species are Cassidulina neoteretis, Cibicidoides lobatulus, and Cassidulina reniforme (outer, inner, and shelf stations, respectively). The dead foraminiferal assemblages show no significant traceable environmental changes in the Kveithola Trough area occurred during the last ca. 100 years. Conversely, the living foraminiferal fauna shows that this area is subject to variations related to circulation changes and organic matter burial in sediments, to which the biota adapts quickly. Moreover, the species that are only observed in the dead foraminiferal assemblages and not in the living CTG-labelled foraminiferal assemblages (e.g. C. reniforme) are typical of colder water and highlight the ongoing warming of the Arctic area. We find that the preservation of foraminiferal tests may bias the paleontological results. The agglutinated tests are often disintegrated, and the delicate calcareous ones are broken. The environmental conditions (style of sedimentation, bottom currents, interaction with other communities) can weaken the foraminiferal tests and make them prone to breakage or dissolution.
... Although the use of diatoms and foraminifera is not required in the bioassessment of coastal and transitional waters (WFD Appendix V), modern communities have been used as bioindicators variously in coastal ecosystems worldwide. However, caution should be made in coastal environments, where the natural background variability might be obscured with human-induced environmental impacts in terms of shared community species composition of diatoms and foraminifera [73,89]. Nonetheless, their fossil remains can indicate the extent of deviation from pre-disturbance conditions by distinguishing if low-diversity opportunistic species are the result of natural or anthropogenic stressed conditions [27]. ...
Ecology can be defined as the study of causes that govern the distribution and abundance of organisms and their relation to the environment. Among benthic microorganisms (10 μm–500 mm), diatoms and foraminifera are of great importance in aquatic ecosystems worldwide because (1) their species react in a rapid and sensitive way to environmental changes in water bodies, and (2) they preserve in sediments for a long time due to their shells, which are made of silica (diatoms) or calcium carbonate or cemented detrital material (foraminifera). In shallow coastal ecosystems (coastal lagoons, marshes), these attributes make foraminifera and diatoms extremely valuable for both ecology and geology because modern communities indicate the dynamic transition between terrestrial and marine habitats, and fossil assemblages record past sea-level changes. While many other works provide specific information on the taxonomy, biology, and ecology of foraminifera and diatoms independently, this chapter aims to provide a comprehensive joint perspective of the applications and uses of these two groups of organisms for environmental studies in coastal habitats. Given the ongoing and future threats associated with sea-level rise and water scarcity, and the lack of long-term monitoring data to assess ecosystems’ deviation from natural baseline conditions, palaeoecological applications of foraminifera and diatoms are also discussed in the context of environmental and restoration policies.
... Ingøydjupet has been formed by an eroding ice sheet, which left Tromsøflaket in higher elevation on the west side, whereas Nordkappbanken mainly has been formed by sediments deposited in front of an ice sheet (Andreassen et al., 2008). In general, coarse-grained sediments are observed at shallow depths due to strong bottom currents, and finer material deposits are observed at deeper depths due to weak currents (Bellec et al., 2008 and references therein;Dijkstra et al., 2013, Junttila et al., 2014. ...
Five stations (≤250 m from the well heads) from three exploration wells of different ages from the SW Barents Sea were studied to investigate the spreading of drill cuttings and sediment quality. Two of the wells were drilled before the restriction of use of oil-based drilling fluids (1993). Elevated concentrations of Ba were found in sediments near all the wells with the highest concentrations at ≤60 m from the well head. The thickness of drill cutting layers was between >20 cm (well head) and 2 cm (250 m from the well head). The sediment quality varied from very bad (oldest well) to background (normal) (newer wells). Regulations led to better sediment quality. Metal concentrations from the oldest well suggested that the top 4 cm of the core represents sediment recovery. However, Ba concentrations of the top sediment layer at all the stations of the three wells indicate no physical recovery.
... The oceanography here is influenced by two major current systems. The southern part is dominated by the north-flowing Norwegian Coastal Current, with relatively cold, low-salinity coastal water while the rest of the bank is influenced by the Norwegian Atlantic Current, bringing relatively warm, saline water to the north (Bellec et al., 2008;Dijkstra et al., 2013;Skarðhamar and Svendsen, 2005). Bottom temperature and salinity average are 4.88C (AE1.5 standard deviation) and 35.1% (AE0.3), ...
Shallow Arctic banks have been observed to harbour rich communities of epifaunal organisms, but have not been well-studied with respect to composition or function due to sampling challenges. In order to determine how these banks function in the Barents Sea ecosystem, we used a combination of video and trawl/dredge sampling at several locations on a heavily trawled bank, Tromsøflaket – located at the southwestern entrance to the Barents Sea. We describe components of the benthic community, and calculate secondary production of dominant epifaunal organisms. Forty-six epibenthic taxa were identified, and sponges were a significant part of the surveyed benthic communities. There were differences in diversity and production among areas, mainly related to the intensity of trawling activities. Gamma was the most diverse and productive area, with highest species abundance and biomass. Trawled areas had considerably lower species numbers, and significant differences in epifaunal abundance and biomass were found between all trawled and untrawled areas. Trawling seem to have an impact on the sponge communities: mean individual poriferan biomass was higher in untrawled areas, and, although poriferans were observed in areas subjected to more intensive trawling, they were at least five times less frequent than in untrawled areas.
... The environmental recovery after remediation action is also detectable in sediment cores by means of benthic foraminifera (Alve et al., 2009). Although most studies on sediment cores, aimed to environmental reconstruction, used the >63 m fraction, also finer (Debenay and Fernandez, 2009) and coarser fractions (Elberling et al., 2003;Nomura and Kawano, 2011;Dijkstra et al., 2013), were considered. However, a reasoned explanation for this choice was not given. ...
Since the 1990s several studies noticed that, along coastal marine areas, the mean size of benthic foraminifera may be reduced due to heavy metal pollution, even if no biometric studies were carried out to quantify this aspect. The Augusta harbour (Sicily, Italy), is characterized by a strong contamination due to several anthropogenic activities, the most important of which are a petrochemical pole and an important industrial harbour. Taking into account the previous studies carried out in the area, which recorded small-sized foraminifera, the present study compared assemblage composition and faunal parameters in the >125 micron and >63 micron fractions of a sediment core collected in the most polluted sector of Augusta harbour. The aim was to understand if the two fractions have comparable environmental significance providing reliable information on the environmental status. In order to quantify the amount of smaller foraminifera in a community and to determine species loss between size fractions, two new indices are used: the Foraminiferal Size Index (FSI) and the Lost Species Index (LSI). Species richness, diversity and composition of the two assemblages were determined to characterize their structure. The results highlighted great depletion and different composition of the >125 micron assemblage with respect to the >63 micron one, showing a selective loss of particular ecological groups (stress-tolerant infaunal taxa). Also the better correlation of Foraminiferal Number (FN) and H’ index of >63 micron fraction with Polychlorobiphenyls (PCBs), Polycyclic Aromatic Hydrocarbons (PAHs), Barium (Ba) and Mercury (Hg), demonstrated the higher reliability of this size fraction for environmental assessment purposes.
... The former includes volcanic and geothermal activities (Olafsson, 1975; Siegel and Siegel, 1978; Nakagawa, 1984; Varekamp and Buseck, 1986; Tomiyasu et al., 2000), and the latter comprises human activities such as combustion of burnable waste, and fossil fuels from thermal power plants, cars, etc. (Nriagu and Pacyna, 1988; Chu and Porcella, 1995; Yokoyama et al., 2000). Atmospheric Hg has circulated all over the world, becoming incorporated into oceans and lakes through its condensation in precipitation (Brosset, 1981; Lindqvist and Rodhe, 1985; Fitzgerald et al., 1991; Iverfeldt, 1991; Lindqvist et al., 1991; Iverfeldt et al., 1995; Keeler et al., 1995; Pirrone et al., 1996; Leermakers et al., 1997; Ames et al., 1998; Dijkstra et al., 2013). Environmental observations today indicate that, similar to the palaeoenvironment without anthropogenic source, atmospheric Hg has been distributed all over the Earth, precipitating in the polar areas. ...
The total mercury content of Quaternary sediments over the last 1.1Ma from IODP Site U1308 drilled in the North Atlantic Ocean has changed, varying with periodicities of 100000 and 41000 years. The Hg content of the sediment increased during glacial periods, associated with increases in ice-rafted debris (IRD), and correlates positively with the total organic carbon (TOC) content and inversely with the absolute abundance of surface-dwelling nannoplankton species. TOC/total nitrogen ratios and δ13Corg values of TOC indicate that the TOC deposited during glacial periods was marine and associated with increased Hg deposition. These observations suggest that marine Hg is incorporated into the organic matter produced by deep-dwelling phytoplankton in the lower photic zone. Mercury- and IRD-bearing icebergs flowed out to this area during glacial periods melt, increasing the Hg content of photic water, and depositing IRD on the ocean floor, where increased marine Hg during glacial periods was consumed by deep-dwelling phytoplankton. Therefore, the change in the sediment Hg content from the North Atlantic Ocean is controlled by climatic change and can be used as a chemical indicator of Northern Hemisphere ice sheet variability.
... digitata X X Knudsen et al. [61] Pullenia bulloides X X X Dijkstra et al. [28] Stainforthia loeblichi X X Steinsund et al. [114] Trifarina angulosa X Ó lafsdóttir et al. [75], Rasmussen et al. [87] Trifarina fluens X X Rytter et al. [102] Arktos (2015) 1:8 Page 11 of 19 8 primary productivity could lead to periods of lower pH that may have encouraged calcareous test dissolution. The latter half of the zone saw the lowest abundance of species related to cold water from the LC (A. gallowayi, C. reniforme, Islandiella spp.). ...
A multiproxy study of marine sediment gravity core AI07-06G from Trinity Bay, Newfoundland, recorded changes in the strength of the Labrador Current (LC) during the Holocene. From ca. 7.2–5.7 cal kyr BP, Trinity Bay’s seafloor was influenced by cooled Atlantic water derived from the West Greenland Current (WGC) Davis Strait branch, merging into the relatively cold LC. This Atlantic water influence gradually decreased after ca. 5.7 cal kyr BP, reaching a minimum at ca. 4.9 cal kyr BP. In contrast, surface temperatures were relatively low due to cold surface water dominated by sea ice and meltwater carried south by the LC. Icebergs from outlet glaciers around Baffin Bay were abundant in the LC prior to ca. 5.5 cal kyr BP. From ca. 4.9–2.9 cal kyr BP, bottom waters became slightly colder and salinity decreased, as increased mixing of the water column brought less saline surface waters towards the seafloor. This may be explained by a weaker North Atlantic subpolar gyre, transporting less Atlantic water from the WGC to the (outer) LC. Arctic meltwater transport was reduced as glacial melting decreased at the end of the Holocene Thermal Optimum. At ca. 2.9 cal kyr BP, bottom waters returned to colder, more stable conditions, indicating a slight decrease in bottom-water ventilation. After ca. 2.1 cal kyr BP, surface water temperatures dropped and sea ice flux increased. The seafloor of Trinity Bay saw warmer conditions, consistent with a stronger subpolar gyre and increased influx of Atlantic-sourced water.
... 250 m to the pile centre. Furthermore, Dijkstra et al. (2013), Terzaghi et al. (1998) and Strømgren et al. (1993) reported negative effects of drill cutting material on aquatic organisms (e.g. severe decline in abundance of benthic foraminifera, crustaceans). ...
Three different synthetic polymers commonly used in drilling fluids (carboxymethyl cellulose - CMC, hydroxyethyl cellulose - HEC and polyacrylamide - PAA) were analysed by off-line-pyrolysis-gas chromatography-mass spectrometry (off-line-Py-GC-MS). The aim of this study was to determine specific environmental marker compounds for the identification of contamination due to drilling activities. In a first step, reference materials of the main constituents of commonly applied water-based drilling fluids were purchased and analysed to identify potential indicator substances. For each polymer a set of two to three specific pyrolysis products was determined. Afterwards, four CMC, one HEC and two PAA based drilling fluids were pyrolysed in order to retrieve the previously identified compounds in drilling fluid mixtures. All indicator compounds were identified. In a third step, spiking experiments on drill cutting samples of various depths of one well proved the traceability of the applied polymers and verified the applicability of the indicator systems in terms of sensitivity and specificity.
... foraminiferal flux values. Differences in microhabitat distribution of benthic foraminifera (Corliss, 1985;Dijkstra et al., 2013) could also potentially cause differences in the foraminiferal assemblage from site to site. However, the overall foraminiferal records are very similar, and the general trends of the major species abundances are in good agreement, suggesting that this is not a significant issue and may at most have caused minor differences between sites. ...
Benthic foraminiferal assemblages supported by selected geochemical data from three marine sediment cores collected in Placentia Bay, SE Newfoundland, are used to construct an ~13,000-year-long record of regional oceanographic changes in the SW Labrador Sea. The area is located in the boundary zone between the cold, ice-loaded Labrador Current (LC) in the north and the warm Gulf Stream (GS) waters to the south. After the Younger Dryas termination, the influence of GS-derived water increased and was further strengthened at 10.7 cal. kyr BP through enhanced northward flow of Atlantic water via the Slopewater Current. A short-term event of increased terrestrial input and water column stratification at 8.4 cal. kyr BP was likely linked to the distal drainage of glacial Lake Agassiz. After 7.3 cal. kyr BP, a stronger LC weakened the inflow of warmer subsurface waters from the GS. This may be explained by extensive meltwater release from ice sheets in Arctic Canada and is concurrent with a general shift in oceanographic conditions in the Labrador Sea region. Around 4.0 cal. kyr BP, conditions became more stable with a slight increase in salinity, indicating a decrease in meltwater transported via the LC. The Northern Hemisphere neoglacial cooling around 2.8 cal. kyr BP was characterized off SE Newfoundland by a further stabilization of the current system, dominated by the LC with some continued influx of GS water.
This paper provides a synthesis of research carried out in the last decade
(2005 till present) on application of foraminifera in pollution monitoring.
Over the years, various characteristics of foraminifera have been applied
for ecotoxicology and pollution monitoring. Rapid change in abundance is
often used as indicators of stressed environment. Presence of stress
tolerant taxa with less tolerant or sensitive taxa has been reported by
many workers from the most polluted sites. Ammonia tepida has been
invariably reported from a majority of the polluted sites, suggesting it to
be a potential bio-indicator species. A few workers, however, suggest that
the preference of A. tepida for fine grained organic carbon rich sediments
may be the reason for its dominance in polluted regions. Tests with
morphological deformities like twinned or reduced chambers, curled or
uncoiled shell, surface protrusions, irregular suture lines, and even
dissolution are common in foraminifera living in polluted regions. A large
increase in laboratory culture studies to understand the response of
foraminifera to specific pollutants has been noted in the last decade.
Laboratory culture studies have led to better discrimination between
natural and anthropogenic changes in the environment.
The seaboard extending from northern Svalbard to Scotland is the only region of the world where fjords have been comprehensively studied for their live (stained) benthic foraminiferal faunas. These modern faunas provide essential baseline data for the interpretation of the postglacial and continuing environmental changes in those fjords and this is the first biogeographic synthesis. The data come from the surface sediment assemblages (mainly sampled in the 1990's) from all the available literature. Due to limited information of shallow water assemblages in the north, only the species occurrences in deeper water from below the halocline are considered. Amongst these, only “common species” species occurring in more than one fjord are included. There is a clear pattern of distribution with five groups of taxa: 5 widespread species found throughout the region; 53 species reaching their northern limit; 13 species reaching their southern limit; 11 deep-sea species; 1 recently introduced species. Although there is an abrupt change in temperature from Tanafjorden in northern Norway to Hornsund in southern Svalbard, the faunal change from N to S is progressive throughout the investigated region. The area of overlap of the northern and southern species corresponds with the previously recognised boundary between the Barents Sea Province and the Norwegian Coast Province based on shelf and upper slope invertebrate macrofaunal benthos and plankton. Temperature is the main abiotic control on the distributions. For the fjords which have shallow sills separating them from the open shelf it is likely that most of the foraminiferal colonisers of the deeper fjord basins are sourced from the shelf or slope via propagules. One species has recently been introduced from further south into the southern region probably through the discharge of ballast water from ships. The biodiversity of the pristine Svalbard fjords extends below what is considered to reflect acceptable ecological status for mainland Norway, illustrating the need to introduce new methods to determine possible deviations from the reference conditions as defined in the EU's Water Framework Directive (WFD; 2000/60/EC). Altogether 347 species have so far been recorded in Norwegian waters: 214 in fjords (60 above and 180 below the halocline of which 26 occur both above and below the halocline) and 266 on the shelf and slope (133 of which also occur in fjords).
In this study we have performed a baseline characterisation of sediment properties in four depositional areas of the Ingøydjupet trough in order to investigate the sediment transport and deposition by ocean currents in the SW Barents Sea. Sedimentation rates, by the 210Pb method, were 1.0–2.4 mm/year and decreasing with distance offshore. Stronger and more variable bottom currents associated with the Norwegian Coastal Current operate nearshore based on the down-core distribution of sortable silt (SS¯) and sediment fractions (clay and silt). These nearshore stations exhibit a trend of decreasing fine sediment supplies and increasing sand content toward present day. The most stable bottom currents are associated with the farthest offshore station which is under the influence of the North Atlantic Current as indicated by the distribution of (SS¯) and also higher TOC contents (0.6–0.9%) compared to nearshore stations (0.4–0.8%). These baseline findings are of relevance for the petroleum industry in planning environmental assessment and monitoring programs connected to the future expansion of industry activities in this region.
A detailed study of foraminiferal populations was carried out at three contaminated sites along the Mediterranean coast of Israel. The unpolluted coast of Nitzanim provided the first natural base line to be determined for the region. At Palmahim (domestic sewage) the species diversity and population density was greatest. Here the largest foraminiferal test sizes and the highest percentage of agglutinated foraminifera were found. In contrast, the lowest species diversity and population density occurred near the Hadera power station, where coal was the major source of pollution in the sediment. Part of Haifa Bay is currently being contaminated by a variety of heavy metals. Benthic foraminifera have been demonstrated to be sensitive in situ monitors or coastal pollution. -from Authors
The Barents Sea is a shallow continental shelf sea. Generally, the physical conditions are determined by three main water masses: Coastal Water, (North) Atlantic Water, and Arctic Water. These three water masses are linked to three different current systems: the Norwegian Coastal Current, the Atlantic Current, and the Arctic Current. This paper gives a brief description of these current systems and their related water masses. Vertical stratification of the different water masses is emphasized since this is important for primary production. Climatic variability is determined by the properties and the activity of the inflowing Atlantic Water. Current activity variations may be explained by external forcing, but may also be a result of processes taking place in the Barents Sea itself. The climatic fluctuations have a significant effect on the ice conditions, which in turn influence the biological production in the northern Barents Sea.
The MAREANO programme (2006 - 2010) has collected video-footage and surface sediment samples in the Southern Barents Sea during the cruise in 2006. The sampled marine areas included Ingøydjupet, a depression that serves as a depositional sink with a predominance of fine-grained muddy sediments. Human impact, both physical and chemical, can be assessed using different methods: Video recordings and geochemical parameters recorded in the sediments reveal evidence of human impact on the sedimentary regime in Ingøydjupet. Bottom trawling fisheries have disturbed the sedimentary surface, and affected benthic organisms and biological communities. The heavy metals mercury (Hg), lead (Pb) and cadmium (Cd), which were analysed in the surface sediments, are of a major concern due to their toxic effects, even at low concentrations. Although there are no serious pollution threats as yet it is evident that increments of Hg and Pb in sediments have increased in recent decades. The most likely cause of these increases is anthropogenic activity, when looking at changes in Hg and Pb concentrations in two 210Pb-dated Ingøydjupet cores. Cadmium does not show a similar temporal trend. The increases in Hg and Pb in Ingøydjupet surface sediments are most likely associated with atmospheric or oceanic long-range transport and deposition in the muddy sediments. The main source for anthropogenic Hg is considered to be coal combustion. Anthropogenic sources for Pb include leaded gasoline, which was in use until the 1970'ies in the western world, and is still in use in other parts of the world.
Previous studies have investigated regional distribution but this is the first attempt to investigate the global biogeographical distribution of individual morphospecies of living/stained smaller benthic foraminifera. From 8032 samples collected between 1952 and 2011 data have been gathered on the relative abundance of >120 species in five major environments ranging from marsh to deep sea. There is a spectrum of six groups of species with abundance ranging from very high (Group 1) to extremely low (Group 6). In the latter species abundance never reaches 10% of an assemblage and, in many cases, it is only 1-2%. Individual species are shown to occupy a range of environments with very few being confined to a single environment (usually either marsh or deep sea). Some species occur in several oceans while others are confined to just one. There is no correlation between species abundance and being either widely or narrowly distributed. Propagules are the most likely mechanism of dispersal but some narrowly distributed species may not produce them. Generalists may be widely or narrowly distributed but opportunists are likely to be widely distributed. The rare species of Group 6 contribute to high diversity in shelf and deep-sea assemblages. These species may be adapted to minor differences in microhabitats induced by disturbance and patchy food supply. Patterns of biogeography have application to ecology, palaeoecology and taxonomy. J. Micropalaeontol. 32(1): 1-58, January 2013.
Both cores reveal an upward transition from a moderately polluted environment represented by a Verneuilina media assemblage to an extremely polluted environment represented by an Eggerelloides scabrus assemblage. This faunal change may result from an increased competitiveness of some shallow water species in deeper water areas exposed to environmental stress, at the expense of more normal marine forms which have stricter ecological requirements. -from Author
The advent of readily available computer-based clustering packages has created some controversy in the micropaleontological community concerning the use and interpretation of computer-based biofacies discrimination. This is because dramatically different results can be obtained depending on methodology. The analysis of various clustering techniques reveals that, in most instances, no statistical hypothesis is contained in the clustering model and no basis exists for accepting one biofacies partitioning over another. Furthermore, most techniques do not consider standard error in species abundances and generate results that are not statistically relevant. When many rare species are present, statistically insignificant differences in rare species can accumulate and overshadow the significant differences in the major species, leading to biofacies containing members having little in common.
A statistically based “error-weighted maximum likelihood” (EWML) clustering method is described that determines biofacies by assuming that samples from a common biofacies are normally distributed. Species variability is weighted to be inversely proportional to measurement uncertainty. The method has been applied to samples collected from the Fraser River Delta marsh and shows that five distinct biofacies can be resolved in the data. Similar results were obtained from readily available packages when the data set was preprocessed to reduce the number of degrees of freedom. Based on the sample results from the new algorithm, and on tests using a representative micropaleontological data set, a more conventional iterative processing method is recommended. This method, although not statistical in nature, produces similar results to EWML (not commercially available yet) with readily available analysis packages. Finally, some of the more common clustering techniques are discussed and strategies for their proper utilization are recommended.
We investigated benthic foraminiferal densities, composition, and microhabitats at three sampling stations on the Portuguese margin, at 980, 1860 and 3125m water depth. For each site, we studied two sets of three replicate cores, sampled during two successive multi-corer deployments. Our results show an overall trend of decreasing foraminiferal densities from the shallowest to the deepest site, in response to a decreasing labile organic matter flux to the sea floor. Faunas at 980m are strongly dominated by Uvigerina mediterranea, which shows a conspicuous faunal density maximum close to the sediment surface. At 1860m, the surface faunas are much poorer, and no longer dominated by a single taxon. Cibicidoides robertsonianus, C. kullenbergi, Uvigerina peregrina, Gavelinopsis translucens and Hoeglundina elegans are present in about equal quantities. The deep infaunal community at these two stations is dominated by Globobulimina affinis, and has comparable densities. At 3125m, the faunas are very poor in 5 of the 6 cores, and mainly consist of agglutinant taxa. At all three stations, important differences are observed between the 6 studied cores. At 980m, the faunal density is about 4 times higher in one of the cores, mainly due to high numbers of Uvigerina mediterranea. This could be explained by the position of this core in a topographical depression, where organic matter concentrates. At 1860m, two sets of three cores, taken during two successive multicorer deployments, contain different amounts of deep infaunal taxa. Finally, at 3125m, one of the 6 cores contains an exceptionally rich deep infaunal community (up to 450 individuals per 50cm), dominated by the calcareous taxa Fursenkoina bradyi, Globobulimina affinis and Chilostomella oolina. The fact that the subrecent fossil faunas of three studied cores from this site are all enriched in these taxa indicates that the observed high infaunal standing stocks are a recurrent phenomenon, in response to a currently unidentified process that strongly concentrates metabolisable organic matter in deeper sediment layers.
A comprehensive, but simple-to-use software package for executing a range of standard numerical analysis and operations used in quantitative paleontology has been developed. The program, called PAST (PAleontological STatistics), runs on standard Windows computers and is available free of charge. PAST integrates spreadsheettype data entry with univariate and multivariate statistics, curve fitting, time-series analysis, data plotting, and simple phylogenetic analysis. Many of the functions are specific to paleontology and ecology, and these functions are not found in standard, more extensive, statistical packages. PAST also includes fourteen case studies (data files and exercises) illustrating use of the program for paleontological problems, making it a complete educational package for courses in quantitative methods.
We present living (stained) benthic foraminifera assemblage data in nine surface sediment samples from the central Barents Sea collected in 2005 and 2006. The abundances of 20 selected species are compared to those from previously published total fauna assemblages of nearby samples. Between 1 and 3 total fauna samples from various years (between 1971 and 1992) are compared with modern (2005 and 2006) samples. The main purpose of the paper is to evaluate the applicability of this comparison. We conclude that, with proper caution, comparing live and total fauna can yield valuable results. Eliminating fragile species, and clustering species according to environmental preferences strengthens the results. A second purpose of the paper is to assess benthic foraminiferal assemblage change in the basin. The data show that foraminiferal assemblage changes vary strongly through out the basin, with maximum change in the extreme north and south of the study area. Division of the species into three major faunal groups related to specific environmental conditions shows that the abundance of cold water species decreases in the eastern part of the study area, while the abundance of warm water species increases in most of the western area. A reverse trend is seen in the most central locality.
Currently some controversy exists in the micropaleontological community concerning the statistically correct number of counts required for quantitative examinations, particularly with respect to the effect of variations in the number ofspedes between samples and the significance of varying fractional abundances on the reliability of results, This analysis of the various statistical methods used to determine the number of required counts has shown that the number of species has no relationship to the number of counts required to measure accurately fractional abundances, As part of the study, logarithmic contours plotting percentage abundance against the total number of specimens, which provide abundance errors at a 95 percent confidence level, have been generated. The plot is displayed logarithmically to emphasize the significance of rare microfossil elements that dominate most assemblages, and which are important in many paleoenvironmental studies. Based on the plot, it is recommended that researchers utilize counts of at least 50 for indicator species having a fractional abundance of approximately 50 percent or greater; 300 counts for species which comprise approximately 10 percent of a sample; 500-1,000 counts for species that make up 5 percent of a sample; and counts of several thousand for defining species that comprise 1 percent ofa sample. It is important to note, however, that where similar biofacies are involved, higher counts are required to accurately distinguish them. It is also recommended that researchers include fractional error abundances with their estimated abundances to provide an indication of their accuracy.
Seafloor organic matter flux from marine primary productivity is quantified, and the range of annual flux rates is calculated and compared to the counts of benthic foraminifera at 382 surface sediment stations from the equatorial Guinea Basin to the Arctic Ocean. Benthic foraminifera show high variability in flux range dependent distributional patterns, with maximum deviations at lowest percentages. The occurrence of a single species covers flux ranges within one to three orders of magnitude. Only a small number of species shows a correlation of this broad range of organic fluxes versus percentages in a count. For C. wuellerstorfi a functional relationship for the recalculation of flux rates from percentages in a count can be given within a standard deviation below 2 g organic carbon [m 2 yr 1]. However, such functions have to be restricted to a specific size range counted. The patterns of dominance more closely scale the environmental optimum of the species in general. For interspecific combinations, these patterns identify the ranges of overlap, where it is impossible to distinguish between higher or lower fluxes on the basis of faunal composition. This is quantified for the co-occurrence of C. wuellerstorfi and U. peregrina near 20% for one species. On an ocean wide scale, a number of taxa can be used to define threshold values for the nutritive needs of the assemblages, most pronounced within annual flux ranges at 2-3 g org. C [m-2]. Different trophic needs of species can be attributed to their infaunal, epibenthic, or opportunistic behavior respectively, and examples for the flux dependent takeover in dominance are given. These quantifications may offer approximations for flux rate dependent faunal patterns in surface sediments and for the detection of flux rate dependent faunal fluctuations in the Quaternary record.
Benthic foraminiferal distributions in polluted marine areas have been investigated over the last three to four decades, and several workers have pointed out that they provide one of the most sensitive and inexpensive markers available for indicating deterioration of marginal marine environments. Most investigations have been carried out in temperate regions, in areas exposed to several pollution sources. Differential adaptations to the complex hydrographical and physical conditions that characterize estuarine environmentals often make it difficult to separate natural faunal properties from pollution effects, especially in a temporal context. Consequently, pollution effects on the biota in estuaries can best be evaluated by comparing the natural, pre-pollution assemblages with those of the present day. The fossil record can also provide a comparative baseline for evaluating to what extent legislation, intending to cause environmental improvements, has had a positive effect. -from Author
Benthic foraminifera are shown to reflect both natural (including climatic) and human-induced environmental alterations over the last 1500 years in Drammensfjord, Norway. Today, Drammensfjord is a 124m deep, partly anoxic, hyposaline basin (salinity <32‰) separated from the adjoining Oslo Fjord by a sill at 10m water depth. It has been affected by human-induced organic pollution for more than a century. Based on major faunal trends, sediment characteristics and concentrations of plant fragments and pollen grains, four environmental zones are distinguished. -from Author
We studied living (Rose Bengal stained) benthic foraminiferal faunas of four replicate cores sampled at a 550m deep station in the Bay ofBiscay in May 2004. After combining our new datawith those collected by Fontanier et al. (2003) at the same station between October 1997 and April 2000, we performed statistical analyses (Detrended Correspondence Analysis) to assess the extent of spatial variability in comparison to temporal variability in our dataset. Replicate cores taken from a single multi-corer deployment and from two deployments were compared so that we could gain insight into spatial variability both at a micro- (less than 1m apart) and meso-scale (around 100m apart). The statistical analyses suggest that the scale of spatial variability is similar to that of temporal variability. Only the most prominent features of temporal variability (i.e. responses to major bloom events) can be recognised. Especially the species Uvigerina peregrina, and to a smaller extent Cibicidoides pachydermus and Siphogenerina columellaris, appear to respond to bulk phytodetritus deposits following surface water primary production maxima. Uvigerina peregrina showed only elevated densities in autumn 1997 and spring 2004, but not in the samples from spring 1999 and 2000. We suggest that these differences could be explained by a difference in the composition of the phytoplankton exported to the seafloor.
We investigated benthic foraminiferal densities, omposition, and microhabitats at three sampling stations on the Portuguese margin, at 980, 1860 and 3125m water depth. For each site, we studied two sets of three replicate cores, sampled during two successive multi-corer deployments. Our results show an overall trend of decreasing foraminiferal densities from the shallowest to the deepest site, in response to a decreasing labile organic matter flux to the sea floor. Faunas at 980m are strongly dominated by Uvigerina mediterranea, which shows a conspicuous faunal density maximum close to the sediment surface. At 1860m, the surface faunas are much poorer, and no longer dominated by a single taxon. Cibicidoides obertsonianus, C. kullenbergi, Uvigerina peregrina, Gavelinopsis translucens and Hoeglundina elegans are present in about equal quantities. The deep infaunal community at these two stations is dominated by Globobulimina affinis, and has comparable densities. At 3125m, the faunas are very poor in 5 of the 6 cores, and mainly consist of agglutinant taxa. At all three stations, important differences are observed between the 6 studied cores. At 980m, the faunal density is about 4 times higher in one of the cores, mainly due to high numbers of Uvigerina mediterranea. This could be explained by the position of this core in a topographical depression, where organic matter concentrates. At 1860m, two sets of three cores, taken during two successive multicorer deployments, contain different amounts of deep infaunal taxa. Finally, at 3125m, one of the 6 cores contains an exceptionally rich deep infaunal community (up to 450 individuals per 50cm), dominated by the calcareous taxa Fursenkoina bradyi, Globobulimina affinis and Chilostomella oolina. The fact that the subrecent fossil faunas of three studied cores from this site are all enriched in these taxa indicates that the observed high infaunal standing stocks are a recurrent phenomenon, in response to a currently unidentified process that strongly concentrates metabolisable organic matter in deeper sediment layers.
Much of the world's surface, even under the oceans, is covered in thick deposits of sedimentary particles - gravel, sand, silt and clay. The nature of the deposits and their formation is very much dependent on the distribution of particles of different sizes. However, different instruments measure different attributes of a particle's size, based on how fast a particle settles in water, or the surface area of a particle, or its length. This book provides information on the how and why of particle size analysis in terms of understanding these sediment deposits.
In this 2006 volume John Murray investigates the ecological processes that control the distribution, abundance and species diversity of benthic foraminifera in environments ranging from marsh to the deepest ocean. To interpret the fossil record it is necessary to have an understanding of the ecology of modern foraminifera and the processes operating after death leading to burial and fossilisation. This book presents the ecological background required to explain how fossil forms are used in dating rocks and reconstructing past environmental features including changes of sea level. It demonstrates how living foraminifera can be used to monitor modern-day environmental change. Ecology and Applications of Benthic Foraminifera presents a comprehensive and global coverage of the subject using all the available literature. It is supported by a website hosting a large database of additional ecological information (www.cambridge.org/0521828392) and will form an important reference for academic researchers and graduate students in Earth and Environmental Sciences. © Cambridge University Press, 2009 and John Murray 2006. All rights reserved.
The deformations of foraminiferal tests have been studied in the genus Ammonia. This study is based on the observations of aberrant test morphology and wall texture using a scanning electron microscope. The various deformations have been classified into eleven groups according to the affected part of the test and to the nature of the deformation. Nine are described in this study. Textural abnormalities in the wall of deformed tests are either crystalline disorganizations or presence of empty cavities. They are always observed in deformed tests. Two hypotheses for the formation of these aberrant textures, related with test deformation, are suggested: 1) crystalline disorganizations may be caused by a stress imposed to the crystalline framework by introduction of alien trace elements, and 2) cavities in the wall probably result from a thickening of the organic matrix that can be caused either by a change in physical and chemical conditions or by food shortage in the environment. These hypotheses are consistent with data reported in the literature which infer that test deformations may have been caused by 1) pollution such as heavy metal contamination; 2) change of physical and chemical parameters; and 3) shortage of nutrients in the environment.
The concentrations of Mn, Ni, Cu, Zn and Cd have been determined on surface and deep water samples from the western North Atlantic. The results from a single vertical profile are compared to published results from the North Pacific and interpreted with respect to the hydrographie characteristics of both oceans. Cd, Zn and Ni have nutrient-type distributions in both oceans. They are depleted in surface waters, increase rapidly across the thermocline, then increase or decrease only slightly with depth. The North Atlantic deep waters at depths of 1 to 3 km have average concentrations of Cd, Zn and Ni equal to 0.29, 1.5 and 5.7 nmol kg⁻¹, respectively; values substantially lower than their corresponding values in the North Pacific at similar depths of 0.94, 8.2 and 10.4 nmol kg⁻¹. Cu concentrations increase gradually with depth in both oceans, with a North Atlantic deep water (1 to 3 km) average value of 1.7 nmol kg⁻¹ relative to 2.7 nmol kg⁻¹ at similar depths in the North Pacific. Mn concentrations decrease with depth through the thermocline with deep North Atlantic values on the order of 0.6 nmol kg⁻¹.
Some of the relatively recent literature correlating morphological variation in benthic foraminifera with environmental parameters is reviewed. It appears some variables (most notably depth) are recorded more frequently, which may affect some conclusions. Although each variable is treated separately, it appears that almost no variables act independently on test morphologies. In reviewing the literature, it bcomes clear that there are many individual trends, especially with shell ornamentation, but few broad ones, and that it is almost impossible, with exception of some of the larger reef-dwelling, symbiont-bearing foraminifera, to predict how any species will react to various parameters. The broad trends concern thinning or thickening of carbonate tests with changing carbonate availability, temperature, and salinity. It appears that many observations of morphological changes within species may not be recorded in the literature. -from Authors
We investigated both living and total assemblages over a 3 year period in a Nova Scotia salt marsh. The results indicate highly variable living populations and assemblages. These variations are generally the result of climatic or micro-environmental changes. Conversely, the total assemblages did not change significantly over the same time period because the total population integrates the small seasonal and spatial variations into a definable assemblage that reliably reflects prevailing marine conditions. Our data indicate that consideration of total associations more accurately depicts modern environments and is, therefore, more useful to most paleoenvironmental studies.- from Authors
Rose Bengal stained foraminifera from box cores, collected in the southern Adriatic Sea along a transect ranging from 146 to 1,200 m water depth, have been studied. Total numbers of supposedly deposit-feeding foraminifera decrease in a fairly regular manner with increasing water depth and distance from land, probably as a consequence of a decreasing flux of organic matter. Suspension-feeding astrorhizid taxa have an irregular distribution, apparently not related to water depth. Highest numbers of stained foraminifera are invariably found at the sediment surface, whereas numbers decrease exponentially deeper in the sediment. Although most species have maximum densities near the sediment surface, a few of the rarer species are concentrated at deeper levels in the sediment. The vertical distribution patterns of a number of common species are variable with depth along the transect, apparently determined by several different environmental parameters.
Volume 1 contains the text of the treatise, and volume 2, 847 plates. Of the 3620 validly proposed generic taxa of Foraminiferida considered 2455 genera are recognised, described and illustrated, 960 regarded as synonyms, 208 considered systematically unrecognisable, 16 too late for detailed inclusion. They are placed in 12 suborders, 74 superfamilies, 296 families, 302 subfamilies. A systematic index is included. The systematic arrangement of genera is alphabetical within the various subfamily or family categories, and the family group taxa within the suborders are arranged in order of presumed evolutionary sequence or increasing complexity. Descriptions are generally focused on test morphology, both external and internal, but some information concerning the living organism is summarized for the few that are known. Geologic range is given to the level of the geologic series of epoch, and known geographic occurrence and a limited amount of ecologic information is included. In view of the very large number of taxa considered, morphologic descriptions are as concise as possible, consistent with the inclusion of the available information. Morphologic terms used are defined in a glossary, in which reference also is given to other terms proposed by various writers. -from Authors
The influence of effluents from cellulose industries on the benthic faunas of comparable fjordic systems on the west coast of Sweden and Scotland is assessed. Generalizations are made about sequential changes in the interrelationship of benthos and sedimentary structure. Estimates are made of the rates of such changes along a gradient of environmental stress brought about by the organic enrichment of marine sediments. Such generalizations may be applicable to a wide range of marine sediments, and can be used to assess the probable effect of large inputs of organic material to a marine sediment. The advantages and disadvantages of using indicator species, comparing faunal groups, and using diversity indices in the description of ecological changes are briefly considered.
Two commonly used benthos samplers, van Veen and Smith-McIntyre, were tested to detect possible adverse characteristics for sampling epibenthic animals. A strong hydraulic disturbance (shock wave) was formed below the van Veen sampler as it descended through the water toward bottom. In this sampler the shock wave was sufficiently strong to force aside unattached benthic animals as long as 8 cm. The Smith-McIntypre sampler created only a weak, oscillatory shock wave. Available information indicates that, under standard operating procedures, the smaller the screened opening in the top of the sampler's jaws the stronger the shock wave.
We studied living (Rose Bengal stained) benthic foraminiferal faunas of four replicate cores sampled at a 550m deep station in the Bay of Biscay in May 2004. After combining our new data with those collected by Fontanier et al. (2003) at the same station between October 1997 and April 2000, we performed statistical analyses (Detrended Correspondence Analysis) to assess the extent of spatial variability in comparison to temporal variability in our dataset. Replicate cores taken from a single multi-corer deployment and from two deployments were compared so that we could gain insight into spatial variability both at a micro-(less than lm apart) and meso-scale (around 100m apart). The statistical analyses suggest that the scale of spatial variability is similar to that of temporal variability. Only the most prominent features of temporal variability (i.e. responses to major bloom events) can be recognised. Especially the species Uvigerina peregrina, and to a smaller extent Cibicidoides pachydermus and Siphogenerina columellaris, appear to respond to bulk phytodetritus deposits following surface water primary production maxima. Uvigerina peregrina showed only elevated densities in autumn 1997 and spring 2004, but not in the samples from spring 1999 and 2000. We suggest that these differences could be explained by a difference in the composition of the phytoplankton exported to the seafloor.
Live benthic foraminifera assemblages from 30 surface sediment samples taken in 2005 and 2006 from the central Barents Sea are compared with total benthic foraminifera assemblages from a database containing samples taken between 1965 and 1992. We evaluate the hypothesis that observed environmental changes in the region have led to observable shifts in benthic foraminiferal fauna. Of the 12 infaunal calcareous species studied marked decreases were observed in cold water species Buccella spp., Elphidium excavatum, Islandiella norcrossi and Nonionellina labradorica. A decline combined with a marked change in spatial distribution is seen in Cassidulina laevigata, Trifarina fluens, Stainforthia loeblichi, Cassidulina reniforme, Cassidulina neoteretis, Melonis barleeanus, and Pullenia bulloides. Warm water species Epistominella nipponica is the only species of these 12 that increased in abundance. The general shift toward dominance of warm water species and temperature tolerant species agrees well with the observed temperature increase in the basin. At the level of individual data points, a relationship between assemblage change and environmental change is not straightforward. The comparison of the new data with the database also displays a shift toward higher abundances of more fragile species, which can be attributed to method differences. The species that display the most pronounced change are those associated with cold water and proximity of the ice edge.The magnitude of benthic foraminiferal change in the study area is largest in a conspicuous belt that appears to follow roughly the Polar Front. This area has a lower temperature and salinity gradient through the last decades than the rest of the study area, and its high faunal change may be due to the position of the Polar Front moving away from this area, and associated changes in the sea ice edge.
We examined the effects of excluding rare species on the comparison of species richness. A river benthic data set and a randomization resampling procedure were used to show the importance of this consideration in aquatic bioassessment in particular. The data set was manipulated by deleting species at three levels of rarity as defined by occurrence frequency: once in all 24 replicates from each of three sites, no more than twice, and no more than five times. We focused on differences in species richness because many other bioassessment metrics are dependent on species richness and species composition. Species abundance patterns at the three sites were very different, with many more rare species at the least impacted site than at the more impacted sites. As sample size increased, the diffcrcnces in species richness among the three sites markedly increased in the original data set. However, the exclusion of rare species at the same level of rarity substantially reduced species richness at the least impacted site but had little effect on the most impacted site. This result led to a serious underestimation of the differences in species richness among the sites in terms of both absolute numbers and species loss percentages. Deleting rare species can damage the sensitivity of community-based methods to detect ecological changes; rare species are critical for bioassessment.
Five 0.25-m2 box cores (four open cores and one vegematic core subdivided in situ into 25 contiguous lo- x lo-cm subcores) reveal that populations of benthic agglutinated Foraminif- era in the central North Pacific are extremely abundant and diverse. As many as 120 species and 10,310 total fragments occur in a single open core, and the Foraminifera outnumber all metazoan taxa combined by at least an order of magnitude. Significant patchiness occurs on both the between-core scale of kilometers and the within-core scale of centimeters. Few species occurred in all cores and those that did were not abundant. Hierarchical classification an d multiple discriminant analysis on the resultant subcore groups in the vegematic core suggest potential interactions between certain species of Foraminifera and such external variables as surface deposit feeders, subsurface deposit feeders, carnivores, filter feeders, biogenic surface structure, and manganese nodules. Multiple regressions of foraminiferan species against all the external variables substantiate the existence of patterns of association. Foraminifera are important components of the benthic fauna, acting, among other things, as predators and disturbance agents. It may well be that they have a more significant effect on the structure and dynamics of deep-sea benthic communities than have any of the metazoan macrofaunal taxa that are the usual objects of deep-sea studies.
Here is the first comprehensive book to describe specific environmental applications of foraminifera and thecamoebians. These organisms permit the biological characterization of a variety of freshwater and coastal marine environments and react quickly to environmental stress, natural or anthropogenic. Their small size and hard shells lead to preservation in large numbers in core samples, allowing their use as proxies to reconstruct past environmental conditions. The book introduces the topic to nonspecialists and then goes on to give detailed descriptions of the methods and techniques. Resource managers and consultants in the public and private sectors who routinely work on coastal environmental problems will find this book invaluable.
Live (rose Bengal stained) foraminiferal faunas of the 63150 pm size fraction have been investigated in surficial sediment (0-1 cm) from mid-shelf to mid-slope environments in the Bay of Biscay. Eleven stations were sampled in April 2002 and March 2004 between 80 and 2000 m water depth (mwd). Earlier studies on the temporal variability of phytoplankton primary production suggest that our stations were sampled at the most eutrophic period of the year. In response to the decrease of exported organic matter flux to the seafloor along our bathymetric transect, foraminiferal standing stocks decrease from similar to 1400-2000 specimens per 50 cm(3) on the continental shelf (100-140 mwd) and upper slope (550 mwd) to about 400 specimens per 50 cm(3) at mid-slope stations (2000 mwd). At all stations, the faunas contain an important amount of small opportunistic species that are favored by seasonal phytodetritus input. On the continental shelf where phytoplankton bloom, events may be geographically restricted; the foraminiferal response is dependent on the distance to the surface-water primary-production cells. Textularia porrecta is very abundant at an 80-m-deep station that is close to the coast and characterized by a high sedimentation rate of fine-grained particles. Foraminiferal faunas are dominated by Nonionella iridea, Cassidulina carinata and Bolivina ex. gr. dilatata at the outer-shelf stations (110-140 mwd) that are under the direct influence of spring bloom phytodetritus input in the northern Bay of Biscay. A fauna dominated by Bolivina dilatatalspathulata and Bolivina subaenariensis is found in the southeastern Bay of Biscay at a 140-m-deep outer-shelf station located seaward of the Adour River estuary, where the sediment is probably enriched in terrestrial organic matter. Apparently, differences in foraminiferal composition between outer-shelf areas in the northern and southeastern Bay of Biscay are related to differences in organic matter quality. On the continental slope, a bathymetric zonation of taxa is observed from upper-slope sites (550-1000 mwd) rich in Epistominella exigua and Uvigerina peregrina to mid-slope stations (1600-2000 mwd), where Nuttallides pusillus and Gavelinopsis translucens dominate the small-sized living fauna. This bathymetric foraminiferal zonation probably reflects a trophic gradient between upper-slope eutrophic stations and mid-slope, more oligotrophic sites. Our zonal description of small-sized living foraminifera (63-150 mu m) is new for the Bay of Biscay and may provide the basis to reconstruct former export production regimes in marginal paleo-environments from temperate latitude areas.
The distribution of living and dead benthic foraminifera in surface sediment samples has been studied. Based on the 13 most important benthic species among a total of 165 species, four assemblages (AS) have been identified using factor analysis: Nonion AS, Trifarina-Cibicides AS, Reophax AS and Epistominella AS. Generally, the faunal assemblages correlate well to summer bottom water temperatures and/or to sediment texture, carbonate content and organic carbon. The Nonion assemblage is positively correlated to the surface sediment pelite content and negatively correlated with the sediment carbonate content. The Trifarina-Cibicides AS correlates to the warmest bottom waters (about 5°C) and coarser sediments. The Reophax AS is found in colder waters (2-4°C) and correlates positively to the organic carbon content in the surface sediments. The Epistominella AS is influenced by reworking. -Authors
Total (predominantly dead) foraminiferal assemblages have been studied at three abyssal sites in the northeast Atlantic Ocean: Porcupine Abyssal Plain (PAP, 49°N, 4,850 m), Madeira Abyssal Plain (MAP, 31°N, 4,950 m) and Cape Verde Abyssal Plain (CVAP, 21°N, 4,505 m). The assemblages are broadly similar at all three sites. Densities at the PAP site (mean 1,395 specimens per 25.5 cm2) are comparable to those at the CVAP site (mean 1,257/25.5 cm2). However, density values are much lower at the MAP site (mean 283/25.5 cm2), almost certainly because of the diluting effect of a Recent turbidite deposit that is presumed to have been devoid of foraminifera when emplaced an estimated 930 years ago. Another important influence on total foraminiferal assemblages is the fact that the PAP site (but not the southern MAP and CVAP sites) is subject to a seasonal pulse of food (phytodetritus), as revealed by time-lapse photography and multiple corer samples. This pulse is reflected in the fact that two species, Epistominella exigua and Alabaminella weddellensis, are more abundant both absolutely and relatively at the PAP site than they are at either of the two southern sites. Both of these species are opportunists that exploit phytodetritus as a food source. Finally, only one calcareous species, Nuttallides umboniferus, is more abundant, both relatively and absolutely, at the two southern sites than at the PAP site. We speculate that, in addition to other factors such as carbonate undersaturated bottom water, it may be adapted to a more oligotrophic food input regime that does not involve substantial pulses of phytodetritus. In general, our results support recent attempts to use certain species as proxy indicators of pulsed organic matter inputs in the paleoceanographic record.
The Western Approaches and Western English Channel are shelf seas strongly influenced by tidal currents and by storms and waves. Surface plankton tows, suspended sediment samples from 40 m below the surface and 5 m above the bottom, and bottom sediment samples have been examined. The water column is commonly rich in the dead foraminifera tests of both planktic and benthic species. These have been used to map the movement of water currents, the breakdown of the thermocline, and to determine residual transport directions. -from Authors
The two morphologically close benthic foraminiferal species, Cassidulina laevigata and C. teretis, were studied in 146 surface-sediment samples in the Norwegian Sea and adjacent shelf areas and in 36 stratigraphic samples from the N Norwegian continental shelf. Q-mode principal component analysis of both the 'living' data and the 'dead' data reveals distinct distribution patterns of C. laevigata and C. teretis, each of which dominates a characteristic assemblage of foraminiferal species. Cassidulina teretis dominates the benthic foraminiferal assemblage on the continental slope of the Norwegian Sea where temperatures of the bottom water masses are approx -1oC and salinities are 34.92per mille. Cassidulina laevigata strongly dominates the benthic foraminiferal assemblage on the N North Sea plateau and is a minor constituent of the benthic foraminiferal assemblage on the Norwegian continental shelf as far N as 72oN. In upper Quaternary sediments on the continental shelf off N Norway, C. teretis was present in various types of glaciomarine paleoenvironments and declined markedly in the early Holocene, whereas C. laevigata increased correspondingly. At 7800yr NP, C. laevigata increased even more strongly. The amelioration of the Holocene climate has favored C. laevigata on the continental shelf off Norway and forced C. teretis to retreat down the continental slope and into the N Barents Sea.-from Authors