Andrés S. Rigual-Hernández

• PhD
• University of Salamanca

The Subantarctic and Polar Frontal zones (SAZ and PFZ) represent a large portion of the total area of the Southern Ocean and serve as a strong sink for atmospheric CO2. These regions are central to hypotheses linking particle fluxes and climate change, yet multi-year records of modern flux and the organisms that control it are, for obvious reasons,...

An array of four sediment trap moorings recorded the particulate flux across the Antarctic Circumpolar Current (ACC) at 170 degrees W. between November 1996 and January 1998, as part of the US JGOFS-Antarctic Environment and Southern Ocean Process Study (AESOPS) program. The trap locations represent sampling within the Polar Frontal Zone, the Antar...

A total of 337 samples collected from five sediment traps located in the Gulf of Lions, Catalan margin and the Alboran Sea have been analyzed in order to study the seasonal, interannual and geographical distributions of silicoflagellate fluxes in the Western Mediterranean. As a general trend, maximum fluxes of silicoflagellate skeletons always occu...

Particle fluxes were recorded over a one-year period (2001-02) in the southern Antarctic Zone in the Australian Sector of the Southern Ocean. Here, we present the results on the seasonal and vertical variability of biogenic particle and diatom valve fluxes. Total mass and diatom fluxes were highly seasonal, with maxima registered during the austral...

Data on marine microfossil assemblage composition has multiple applications. Initially, it was primarily used for (chrono)stratigraphy and palaeoecology, but these data are now also widely used to study evolutionary and ecological processes, such as past biodiversity and its links with environmental dynamics, or to provide a basis for conservation...

This study investigates the abundance, composition, and biogeographical distribution of coccolithophores in the water column of the northwestern Iberian coastal upwelling system during late summer 2022. Coccolithophore data were compared with in situ measurements of physical, chemical, and biological parameters, as well as with satellite data and t...

The Sicily Channel, located in the central Mediterranean Sea, represents a key point for the regional oceanographic circulation, as it is regarded as the sill that separates the western and eastern basins. Therefore, it is regarded as a unique zone in the well-documented west-to-east Mediterranean productivity gradient. Here we present a time serie...

Pteropods are a group of cosmopolitan holoplanktic gastropods that produce an aragonite shell and play an important role in both marine ecosystems and geochemical cycles. In addition to being affected by anthropogenic impacts that include warming and changes in carbonate system parameters, the Mediterranean Sea is considered to be understudied conc...

The Sicily Strait, located in the central Mediterranean Sea, represents a key point for the regional oceanographic circulation as it is considered the sill that separates the western and eastern basins. Therefore, it is considered a unique zone regarding the well-documented west-to-east Mediterranean productivity gradient. Here we document the plan...

Evolutionary or adaptative changes in Noelaerhabdaceae coccolithophores occurred in parallel with major changes in carbonate export and burial during scenarios of low orbital eccentricity, with a ∼400 kyr recurrence, during the Pleistocene. Coeval with these conditions of enhanced proliferation, here we report that the calcification of specimens wa...

The Subantarctic Zone of the Southern Ocean plays a disproportionally large role on the Earth system. Model projections predict rapid environmental change in the coming decades, including ocean acidification, warming, and changes in nutrient supply which pose a serious risk for marine ecosystems. Yet despite the importance of the Subantarctic Zone,...

Planktonic Foraminifera are unique paleo-environmental indicators through their excellent fossil record in ocean sediments. Their distribution and diversity are affected by different environmental factors including anthropogenically forced ocean and climate change. Until now, historical changes in their distribution have not been fully assessed at...

Evolutionary or adaptative changes in Noelaerhabdaceae coccolithophores occurred in parallel with major changes in carbonate export and burial during scenarios of low orbital eccentricity, with a ~ 400 kyr recurrence, during the Pleistocene. Coeval with these conditions of enhanced proliferation, here we report a globally enhanced calcification int...

The Mediterranean Sea sustains a rich and fragile ecosystem currently threatened by multiple anthropogenic impacts that include, among others, warming, pollution, and changes in seawater carbonate speciation associated to increasing uptake of atmospheric CO2. This environmental change represents a major risk for marine calcifiers such as planktonic...

The aim of this work is to investigate the variability of planktic foraminifera calcification in the northwestern Mediterranean Sea on seasonal, interannual and pre-industrial Holocene time scales. This study is based on data from a 12-year-long sediment trap record retrieved in the in the Gulf of Lions and seabed sediment samples from the Gulf of...

Calcareous nannofossil assemblages and fragmentation ratios of two coccolithophore species (Coccolithus pelagicus and Calcidiscus leptoporus) were analysed in samples from ODP Site 1090, South Atlantic (42° 54.8′S, 8° 53.9′E), to obtain valuable insights into the paleoceanographic evolution and carbonate preservation trends during the late Pliocene...

Ocean Acidification (OA) is considered a major threat and is projected to impact all areas of global ocean, therefore understanding its ecological impacts remains a priority for science and management. The Mediterranean Sea is considered a highly vulnerable region, so we analyzed material coming from Planier sediment trap in order to characterize t...

Changes in Southern Ocean biogeochemistry: observations from moored observatory, remote access sampling, sensor arrays.

Long-chain unsaturated alkenones produced by haptophyte algae are widely used as paleotemperature indicators. The unsaturation relationship to temperature is linear at mid-latitudes, however, non-linear responses detected in subpolar regions of both hemispheres have suggested complicating factors in these environments. To assess the influence of bi...

The Southern Ocean absorbs a great deal of heat and carbon dioxide (CO2) from the atmosphere, helping to shape the global climate. This oceanic service comes at a cost: the Southern Ocean is becoming warmer, fresher, less oxygenated, and more acidic—in effect heating up, losing breath, and becoming corrosive. The consequences of these changes are d...

The Chatham Rise supports some of New Zealand's most economically valuable commercial fish stocks, fuelled by the highly productive waters of the Subtropical Frontal Zone (STFZ). Climate change-related shifts in phytoplankton community structure and function are predicted and may affect Chatham Rise productivity and deep-sea carbon sequestration by...

A high-resolution study of the MIS 12/MIS 11 transition and the MIS 11 (430–376 kyr) coccolithophore assemblages at Ocean Drilling Program Site 977 was conducted to reconstruct the palaeoceanographic and climatic changes in the Alboran Sea from the variability in surface water conditions. The nannofossil record was integrated with the planktonic ox...

The Southern Ocean is warming faster than the average global ocean and is particularly vulnerable to ocean acidification due to its low temperatures and moderate alkalinity. Coccolithophores are the most productive calcifying phytoplankton and an important component of Southern Ocean ecosystems. Laboratory observations on the most abundant coccolit...

Ocean acidification is expected to have detrimental consequences for the most abundant calcifying phytoplankton species Emiliania huxleyi. However, this assumption is mainly based on laboratory manipulations that are unable to reproduce the complexity of natural ecosystems. Here, E. huxleyi coccolith assemblages collected over a year by an autonomo...

Southern Ocean waters are projected to undergo profound changes in their physical and chemical properties in the coming decades. Coccolithophore blooms in the Southern Ocean are thought to account for a major fraction of the global marine calcium carbonate (CaCO3) production and export to the deep sea. Therefore, changes in the composition and abun...

Southern Ocean waters are projected to undergo profound changes in their physical and chemical properties in the coming decades. Coccolithophore blooms in the Southern Ocean are thought to account for a major fraction of the global marine calcium carbonate (CaCO3) production and export to the deep sea. Therefore, changes in the composition and abun...

Some aspects of the life cycle of the Southern Ocean diatom Fragilariopsis kerguelensis have been investigated previously, but many of its details have not been surveyed in nature. We investigated material from a two-year sediment trap time series by high-throughput imaging and image analysis, looking for morphometric signals of life cycle stages....

Figure S3. Relationship between valve width and apical length shows a much clearer separation than aspect ratio, and substantially less dependence on apical length.

Table S2. Valve width ranges of the three species when considering (a) only specimens identified in full agreement (unequivocal); (b) specimens identified as belonging to the species considered by the majority of participants (majority); and (c) by any single participant (single vote).

Figure S1. Validation of striae density measurement by SHERPA (on the x‐axis) versus measured manually (on the y‐axis). Black line: y=x. Red line: least squares regression line.

Figure S2. Dependence of identification agreement on apical valve length. The gray line represents the percentage of specimens within a 10 μm broad apical length range which received at least 90% identical taxonomic labels; the black dotted line depicts the absolute number of these cases within the 10 μm size window. The solid black line depicts th...

Figure S4. Eccentricity of the broadest valve position along the apical axis hardly depends on apical length, and is slightly higher (away from 0.5 on the y‐axis) in Fragilariopsis ritscheri than in the other two species.

Table S1. Apical valve length ranges of the three species when considering (a) only specimens identified in full agreement (unequivocal); (b) specimens identified as belonging to the species considered by the majority of participants (majority); and (c) by any single participant (single vote).

Table S3. Striae density ranges of the three species when considering (a) only specimens identified in full agreement (unequivocal); (b) specimens identified as belonging to the species considered by the majority of participants giving an identification for that specimen (majority); and (c) by any single participant (single vote).

Semi‐automated methods for microscopic image acquisition, image analysis and taxonomic identification have repeatedly received attention in diatom analysis. Less well studied is the question whether and how such methods might prove useful for clarifying the delimitation of species that are difficult to separate for human taxonomists. To try to answ...

The Antarctic Zone, the southernmost belt of the Antarctic Circumpolar Current, plays an important role in the control of atmospheric carbon dioxide concentrations. In the last decade, a number of studies have highlighted the importance of diatom assemblage composition in influencing the magnitude of the organic carbon and biogenic silica fluxes ex...

The Southern Ocean is experiencing rapid and relentless change in its physical and biogeochemical properties. The rate of warming of the Antarctic Circumpolar Current exceeds that of the global ocean, and the enhanced uptake of carbon dioxide is causing basin-wide ocean acidification. Observational data suggest that these changes are influencing th...

The Southern Ocean is experiencing rapid and relentless change in its physical and biogeochemical properties. The rate of warming of the Antarctic Circumpolar Current exceeds that of the global ocean, and the enhanced uptake of carbon dioxide is causing basin-wide ocean acidification. Observational data suggest that these changes are influencing th...

The Subantarctic Zone (SAZ) plays a crucial role in global carbon cycling as a significant sink for atmospheric CO2. In the Australian sector, the SAZ exports large quantities of organic carbon from the surface ocean, despite lower algal biomass accumulation in surface waters than other Southern Ocean sectors. We present the first analysis of diato...

A marine sediment core retrieved from the middle continental slope of the northwestern Barents Sea was analyzed for its geochemical (alkenones) and micropalaeontological (diatoms, coccolithophores and dinocyst) content in order to reconstruct the evolution of upper ocean conditions and ice-sheet dynamics during the last 25 kyr. Additionally, quanti...

Carbon isotopic fractionation during photosynthesis (εp) is used to reconstruct past CO2 and phyto-plankton growth rates, typically by measuring the δ13C of biomarkers produced by coccolithophorids. However, organic molecules bound within diatom frustules represent another phase for measurement of δ13C and offer the opportunity to obtain εpfor spec...

Phytobites - Australasian Society for Phycology and Aquatic Botany Newsletter

This study reports detailed silicoflagellate assemblage composition and annual seasonal flux from sediment traps at four locations along a transect across the Southern Ocean frontal systems. The four traps sampled the central Subantarctic Zone (SAZ, 47°S site), the Subantarctic Front (SAF, 51°S site), the Polar Frontal Zone (PFZ, 54°S site) and the...

During the PROMESS campaign (summer 2004) a borehole (PRGL1) was drilled in the upper slope of the Gulf of Lions. Previous studies showed that the deposition of the sedimentary units at borehole PRGL1 was determined by changes in the discharge of the Rhone river, induced by sea level and climate variability with a strong 100 ka imprint. However, th...

During the PROMESS campaign (summer 2004) a borehole (PRGL1) was drilled in the upper slope of the Gulf of Lions covering the last 530 kyr. Here, we present new biomarker data from 440–528 kyr in order to reconstruct past climate variability, sea surface temperature (SST) (alkenone-based) and oxygenation of the bottom waters (based on n-hexacosanol...

The Southern Ocean plays a pivotal role in the control of atmospheric CO2 levels, via both physical and biological sequestration processes. The biological carbon transfer to the ocean interior is tightly coupled to the availability of other elements, especially iron as a trace limiting nutrient and dissolved silicon (DSi) as the mineral substrate t...

Download directly from: https://www1.data.antarctica.gov.au/aadc/metadata/metadata.cfm?entry_id=AAS_4078_Diatom_Images. ABSTRACT: The collection aims to showcase the range of Southern Ocean diatom species found in the major hydrological provinces of the Australian Sector of the Southern Ocean along the 140 degrees E. The collection includes specime...

REVISION ACCEPTED 31/8/15 (http://www.biogeosciences-discuss.net/12/8615/2015/bgd-12-8615-2015.html). Abstract: The Subantarctic and Polar Frontal zones (SAZ and PFZ) represent a large portion of the total area of the Southern Ocean and serve as a strong sink for atmospheric CO2. These regions are central to hypotheses linking particle fluxes and c...

An array of four sediment trap moorings recorded the particulate flux across the Antarctic Circumpolar Current (ACC) at 170 °W, between November 1996 and January 1998, as part of the US JGOFS-Antarctic Environment and Southern Ocean Process Study (AESOPS) program. The trap locations represent sampling within the Polar Frontal Zone, the Antarctic Po...

The depositional history of the Storfjorden and Kveithola trough-mouth fans (TMFs) in the northwestern Barents Sea has been investigated within two coordinated Spanish and Italian projects in the framework of the International Polar Year (IPY) Activity 367, NICE STREAMS. The investigation has been conducted using a multidisciplinary approach to the...

We examined the total diatom flux and species composition, total coccolith flux and total mass flux collected with a sediment trap between October 1993 and January 2006 in the northeastern entrance of the Gulf of Lions (North Western Mediterranean). The average daily diatom and coccolith fluxes (3 × 107 valves m2 d–1 and 6.1 × 108 coccoliths m2 day...

This study is presented in the context of the Spanish research project "The development of an Arctic ice stream-dominated sedimentary system: The southern Svalbard continental margin" (SVAIS), developed within the framework of the International Polar Year (IPY) Activity N. 367 (NICE STREAMS). Its main goal is to understand the evolution of glacial...

We studied the seasonal and annual evolution of the diatom assemblages through the analysis of two sediment trap records from the Gulf of Lions (Northwest Mediterranean). The general circulation in the GoL is dominated by an along-slope current called Northern Current (NC) that flows in a cyclonic direction along the continental slope Particle flux...