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Heather Stoll - One of the best experts on this subject based on the ideXlab platform.
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an isotope label method for empirical detection of carbonic anhydrase in the calcification pathway of the Coccolithophore emiliania huxleyi
2021Co-Authors: Chuanlian Liu, Sonia Blancoameijeiras, Hongrui Zhang, Brian M Hopkinson, Stefano M Bernasconi, Luz Maria Mejia, Heather StollAbstract:Abstract Coccolithophores are a group of phytoplankton widely distributed in the ocean, which secrete extracellular calcite plates termed coccoliths. Coccoliths have been increasingly employed as an archive for geochemical, ecological and paleoclimate studies in recent years. A robust application of coccolith-based geochemical proxies relies on understanding the carbon acquisition strategies and the pathways of carbon supply for calcification. Carbonic anhydrase (CA) plays important roles in the carbon concentrating mechanism s of aquatic algae and potentially also in calcification. However, it is difficult to independently assess the role of CA in carbon supply for photosynthesis versus calcification. To fill this gap, we explored a new method to detect the CA activity inside Coccolithophore. To achieve this, Coccolithophores were cultured with oxygen and carbon isotope labeled dissolved inorganic carbon (DIC). By exploiting the different behavior of oxygen and carbon isotopes with (sea)water, this double label method can elucidate the significance of CA activity in the calcification pathway. Application of this method to Emiliania huxleyi shows that CA is present in the calcification pathway, and that there is no significant difference in the CA activity between a high and low CO2 treatment. However, under low CO2 treatment E. huxleyi enhanced the bicarbonate pumping rate on both cell and chloroplast membranes. This novel method could be performed on other species of Coccolithophores in the future and have a potential to extend our knowledge on coccolith oxygen isotope vital effects.
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Coccolithophore productivity at the western iberian margin during the middle pleistocene 310 455 ka evidence from coccolith sr ca data
2020Co-Authors: Heather Stoll, Karlheinz Baumann, Antje Hl Voelker, Catarina Cavaleiro, Michal KuceraAbstract:Abstract. Coccolithophores contribute significantly to marine primary productivity and play a unique role in ocean biogeochemistry by using carbon for photosynthesis (soft-tissue pump) and for calcification (carbonate counter pump). Despite the importance of including Coccolithophores in Earth system models to allow better predictions of the climate system's responses to planetary change, the reconstruction of Coccolithophore productivity mostly relied on proxies dependent on accumulation and sedimentation rates and preservation conditions. In this study we used an independent proxy, based on the coccolith fraction (CF) Sr∕Ca ratio, to reconstruct Coccolithophore productivity. We studied the marine sediment core MD03-2699 from the western Iberian margin (IbM), concentrating on glacial–interglacial cycles of Marine Isotopic Stage (MIS) 12 to MIS 9. We found that IbM Coccolithophore productivity was controlled by changes in the oceanographic conditions, such as in sea surface temperature (SST) and nutrient availability, and by competition with other phytoplankton groups. Long-term Coccolithophore productivity was primarily affected by variations in the dominant surface water mass. Polar and subpolar surface waters during glacial substages were associated with decreased Coccolithophore productivity, with the strongest productivity minima concomitant with Heinrich-type events (HtEs). Subtropical, nutrient-poorer waters, increased terrigenous input, and moderate to strong upwelling during the deglaciation and early MIS11 are hypothesized to have attributed a competitive advantage to diatoms to the detriment of Coccolithophores, resulting in intermediate Coccolithophore productivity levels. During the progression towards full glacial conditions an increasing presence of nutrient-richer waters, related to the growing influence of transitional surface waters and/or intensified upwelling, probably stimulated Coccolithophore productivity to maxima following the rapid depletion of silica by diatoms. We present conceptual models of the carbon and carbonate cycle components for the IbM in different time slices that might serve as a basis for further investigation and modelling experiments.
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insolation forcing of Coccolithophore productivity in the north atlantic during the middle pleistocene
2018Co-Authors: Heather Stoll, Karlheinz Baumann, Antje Hl Voelker, Catarina Cavaleiro, Denise K Kulhanek, Bernhard David A Naafs, Ruediger Stein, Jens Grutzner, C VenturaAbstract:Coccolithophores play a key role in the oceanic carbon cycle through the biological and carbonate pumps. Understanding controls on Coccolithophore productivity is thus fundamental to quantify oceanic carbon cycling. We investigate changes in Coccolithophore productivity over several Pleistocene glacial-interglacial cycles using a high-resolution coccolith Sr/Ca ratio record, which is an indicator of growth rate and thus a proxy for Coccolithophore productivity. We use Middle Pleistocene sediments from the North Atlantic Integrated Ocean Drilling Program (IODP) Site U1313 (41.00′ N, 32.58’ W) spanning Marine Isotopic Stages 16 to 10 (638–356 kyr). The location of the record allows us to investigate processes affecting productivity in a mid-latitude setting and to unravel the effects of temperature and regional ocean circulation. Coccolithophore productivity shows a dominant glacial-interglacial cyclicity with higher productivity during glacials, which appears to reflect the southward migration of the North Atlantic high productivity zone currently located between 45° and 55° N. Spectral analysis of the productivity record reveals a suborbital variability consistent with forcing by insolation maxima superimposed on the front migration pattern. Similar to today, Coccolithophore productivity during interglacials was enhanced when insolation was at its maximum in spring or in autumn, whereas during glacials, productivity was enhanced when summer/autumn insolation was at its maximum. We show that in the studied region, Coccolithophore productivity was driven by processes reflecting regional insolation. Applying this information to model experiments is required to assess if Coccolithophore productivity played a significant role in past changes of atmospheric CO2.
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late miocene threshold response of marine algae to carbon dioxide limitation
2013Co-Authors: Clara T Bolton, Heather StollAbstract:New measurements of stable isotope vital effects in fossil coccoliths show a step increase in reliance of Coccolithophore photosynthesis on active transport of dissolved bicarbonate in the late Miocene epoch, suggesting both a low threshold for adaptation of Coccolithophores to carbon dioxide and a decrease in global carbon dioxide levels at that time. Coccolithophores, widely distributed in the marine plankton, are unique among algae in that they use carbon for both calcification and photosynthesis. In this study Clara Bolton and Heather Stoll use a model of cellular carbon fluxes to show that when carbon dioxide concentrations are low, these organisms will allocate carbon preferentially to photosynthesis rather than to calcification, particularly in larger cells. This is reflected in a difference between the isotopic signature of small and large coccoliths that diminishes at high levels of carbon dioxide. This pattern can be seen in the fossil record; the authors identify an isotopic divergence between small and large coccoliths at around 6 million years ago, and interpret this as a threshold response of the cells' carbon acquisition to a global decrease in carbon dioxide concentrations at the time. Coccolithophores are marine algae that use carbon for calcification and photosynthesis. The long-term adaptation of these and other marine algae to decreasing carbon dioxide levels during the Cenozoic era1 has resulted in modern algae capable of actively enhancing carbon dioxide at the site of photosynthesis. This enhancement occurs through the transport of dissolved bicarbonate (HCO3−) and with the help of enzymes whose expression can be modulated by variable aqueous carbon dioxide concentration, [CO2], in laboratory cultures2,3. Coccolithophores preserve the geological history of this adaptation because the stable carbon and oxygen isotopic compositions of their calcite plates (coccoliths), which are preserved in the fossil record, are sensitive to active carbon uptake and transport by the cell. Here we use a model of cellular carbon fluxes and show that at low [CO2] the increased demand for HCO3− at the site of photosynthesis results in a diminished allocation of HCO3− to calcification, which is most pronounced in larger cells. This results in a large divergence between the carbon isotopic compositions of small versus large coccoliths only at low [CO2]. Our evaluation of the oxygen and carbon isotope record of size-separated fossil coccoliths reveals that this isotopic divergence first arose during the late Miocene to the earliest Pliocene epoch (about 7–5 million years ago). We interpret this to be a threshold response of the cells’ carbon acquisition strategies to decreasing [CO2]. The documented Coccolithophore response is synchronous with a global shift in terrestrial vegetation distribution between 8 and 5 Myr ago, which has been interpreted by some studies as a floral response to decreasing partial pressures of carbon dioxide ( ) in the atmosphere4,5,6. We infer a global decrease in carbon dioxide levels for this time interval that has not yet been identified in the sparse proxy record7 but is synchronous with global cooling and progressive glaciations8,9.
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vital effects in coccolith calcite cenozoic climate pco2 drove the diversity of carbon acquisition strategies in Coccolithophores
2012Co-Authors: Clara T Bolton, Heather Stoll, Ana MendezvicenteAbstract:[1] Coccoliths, calcite plates produced by the marine phytoplankton Coccolithophores, have previously shown a large array of carbon and oxygen stable isotope fractionations (termed “vital effects”), correlated to cell size and hypothesized to reflect the varying importance of active carbon acquisition strategies. Culture studies show a reduced range of vital effects between large and small Coccolithophores under high CO2, consistent with previous observations of a smaller range of interspecific vital effects in Paleocene coccoliths. We present new fossil data examining Coccolithophore vital effects over three key Cenozoic intervals reflecting changing climate and atmospheric partial pressure of CO2 (pCO2). Oxygen and carbon stable isotopes of size-separated coccolith fractions dominated by different species from well preserved Paleocene-Eocene thermal maximum (PETM, ∼56 Ma) samples show reduced interspecific differences within the greenhouse boundary conditions of the PETM. Conversely, isotope data from the Plio-Pleistocene transition (PPT; 3.5–2 Ma) and the last glacial maximum (LGM; ∼22 ka) show persistent vital effects of ∼2‰. PPT and LGM data show a clear positive trend between coccolith (cell) size and isotopic enrichment in coccolith carbonate, as seen in laboratory cultures. On geological timescales, the degree of expression of vital effects in coccoliths appears to be insensitive topCO2 changes over the range ∼350 ppm (Pliocene) to ∼180 ppm (LGM). The modern array of coccolith vital effects arose after the PETM but before the late Pliocene and may reflect the operation of more diverse carbon acquisition strategies in Coccolithophores in response to decreasing Cenozoic pCO2.
Catarina Cavaleiro - One of the best experts on this subject based on the ideXlab platform.
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Coccolithophore productivity at the western iberian margin during the middle pleistocene 310 455 ka evidence from coccolith sr ca data
2020Co-Authors: Heather Stoll, Karlheinz Baumann, Antje Hl Voelker, Catarina Cavaleiro, Michal KuceraAbstract:Abstract. Coccolithophores contribute significantly to marine primary productivity and play a unique role in ocean biogeochemistry by using carbon for photosynthesis (soft-tissue pump) and for calcification (carbonate counter pump). Despite the importance of including Coccolithophores in Earth system models to allow better predictions of the climate system's responses to planetary change, the reconstruction of Coccolithophore productivity mostly relied on proxies dependent on accumulation and sedimentation rates and preservation conditions. In this study we used an independent proxy, based on the coccolith fraction (CF) Sr∕Ca ratio, to reconstruct Coccolithophore productivity. We studied the marine sediment core MD03-2699 from the western Iberian margin (IbM), concentrating on glacial–interglacial cycles of Marine Isotopic Stage (MIS) 12 to MIS 9. We found that IbM Coccolithophore productivity was controlled by changes in the oceanographic conditions, such as in sea surface temperature (SST) and nutrient availability, and by competition with other phytoplankton groups. Long-term Coccolithophore productivity was primarily affected by variations in the dominant surface water mass. Polar and subpolar surface waters during glacial substages were associated with decreased Coccolithophore productivity, with the strongest productivity minima concomitant with Heinrich-type events (HtEs). Subtropical, nutrient-poorer waters, increased terrigenous input, and moderate to strong upwelling during the deglaciation and early MIS11 are hypothesized to have attributed a competitive advantage to diatoms to the detriment of Coccolithophores, resulting in intermediate Coccolithophore productivity levels. During the progression towards full glacial conditions an increasing presence of nutrient-richer waters, related to the growing influence of transitional surface waters and/or intensified upwelling, probably stimulated Coccolithophore productivity to maxima following the rapid depletion of silica by diatoms. We present conceptual models of the carbon and carbonate cycle components for the IbM in different time slices that might serve as a basis for further investigation and modelling experiments.
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insolation forcing of Coccolithophore productivity in the north atlantic during the middle pleistocene
2018Co-Authors: Heather Stoll, Karlheinz Baumann, Antje Hl Voelker, Catarina Cavaleiro, Denise K Kulhanek, Bernhard David A Naafs, Ruediger Stein, Jens Grutzner, C VenturaAbstract:Coccolithophores play a key role in the oceanic carbon cycle through the biological and carbonate pumps. Understanding controls on Coccolithophore productivity is thus fundamental to quantify oceanic carbon cycling. We investigate changes in Coccolithophore productivity over several Pleistocene glacial-interglacial cycles using a high-resolution coccolith Sr/Ca ratio record, which is an indicator of growth rate and thus a proxy for Coccolithophore productivity. We use Middle Pleistocene sediments from the North Atlantic Integrated Ocean Drilling Program (IODP) Site U1313 (41.00′ N, 32.58’ W) spanning Marine Isotopic Stages 16 to 10 (638–356 kyr). The location of the record allows us to investigate processes affecting productivity in a mid-latitude setting and to unravel the effects of temperature and regional ocean circulation. Coccolithophore productivity shows a dominant glacial-interglacial cyclicity with higher productivity during glacials, which appears to reflect the southward migration of the North Atlantic high productivity zone currently located between 45° and 55° N. Spectral analysis of the productivity record reveals a suborbital variability consistent with forcing by insolation maxima superimposed on the front migration pattern. Similar to today, Coccolithophore productivity during interglacials was enhanced when insolation was at its maximum in spring or in autumn, whereas during glacials, productivity was enhanced when summer/autumn insolation was at its maximum. We show that in the studied region, Coccolithophore productivity was driven by processes reflecting regional insolation. Applying this information to model experiments is required to assess if Coccolithophore productivity played a significant role in past changes of atmospheric CO2.
Alex J Poulton - One of the best experts on this subject based on the ideXlab platform.
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haplo diplontic life cycle expands Coccolithophore niche
2021Co-Authors: Joost C De Vries, Gerald Langer, Alex J Poulton, Fanny M Monteiro, Glen L Wheeler, Jelena Godrijan, Federica Cerino, Elisa Malinverno, Colin BrownleeAbstract:Abstract. Coccolithophores are globally important marine calcifying phytoplankton that utilize a haplo-diplontic life cycle. The haplo-diplontic life cycle allows Coccolithophores to divide in both life cycle phases and potentially expands Coccolithophore niche volume. Research has, however, to date largely overlooked the life cycle of Coccolithophores and has instead focused on the diploid life cycle phase of Coccolithophores. Through the synthesis and analysis of global scanning electron microscopy (SEM) Coccolithophore abundance data ( n=2534 ), we find that calcified haploid Coccolithophores generally constitute a minor component of the total Coccolithophore abundance ( ≈ 2 %–15 % depending on season). However, using case studies in the Atlantic Ocean and Mediterranean Sea, we show that, depending on environmental conditions, calcifying haploid Coccolithophores can be significant contributors to the Coccolithophore standing stock (up to ≈30 %). Furthermore, using hypervolumes to quantify the niche of Coccolithophores, we illustrate that the haploid and diploid life cycle phases inhabit contrasting niches and that on average this allows Coccolithophores to expand their niche by ≈18.8 %, with a range of 3 %–76 % for individual species. Our results highlight that future Coccolithophore research should consider both life cycle stages, as omission of the haploid life cycle phase in current research limits our understanding of Coccolithophore ecology. Our results furthermore suggest a different response to nutrient limitation and stratification, which may be of relevance for further climate scenarios. Our compilation highlights the spatial and temporal sparsity of SEM measurements and the need for new molecular techniques to identify uncalcified haploid Coccolithophores. Our work also emphasizes the need for further work on the carbonate chemistry niche of the Coccolithophore life cycle.
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ocean warming not acidification controlled Coccolithophore response during past greenhouse climate change
2016Co-Authors: Samantha J Gibbs, Alex J Poulton, Jeremy R Young, Sarah A Odea, Paul R Bown, Andy RidgwellAbstract:Current carbon dioxide emissions are an assumed threat to oceanic calcifying plankton (Coccolithophores) not just due to rising sea-surface temperatures, but also because of ocean acidification (OA). This assessment is based on single species culture experiments that are now revealing complex, synergistic, and adaptive responses to such environmental change. Despite this complexity, there is still a widespread perception that Coccolithophore calcification will be inhibited by OA. These plankton have an excellent fossil record, and so we can test for the impact of OA during geological carbon cycle events, providing the added advantages of exploring entire communities across real-world major climate perturbation and recovery. Here we target fossil Coccolithophore groups (holococcoliths and braarudosphaerids) expected to exhibit greatest sensitivity to acidification because of their reliance on extracellular calcification. Across the Paleocene-Eocene Thermal Maximum (56 Ma) rapid warming event, the biogeography and abundance of these extracellular calcifiers shifted dramatically, disappearing entirely from low latitudes to become limited to cooler, lower saturation-state areas. By comparing these range shift data with the environmental parameters from an Earth system model, we show that the principal control on these range retractions was temperature, with survival maintained in high-latitude refugia, despite more adverse ocean chemistry conditions. Deleterious effects of OA were only evidenced when twinned with elevated temperatures.
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phenological characteristics of global Coccolithophore blooms
2015Co-Authors: Toby Tyrrell, Stuart C Painter, Jason Hopkins, Stephanie A Henson, Alex J PoultonAbstract:Coccolithophores are recognized as having a significant influence on the global carbon cycle through the production and export of calcium carbonate (often referred to as particulate inorganic carbon or PIC). Using remotely sensed PIC and chlorophyll data, we investigate the seasonal dynamics of Coccolithophores relative to a mixed phytoplankton community. Seasonal variability in PIC, here considered to indicate changes in Coccolithophore biomass, is identified across much of the global ocean. Blooms, which typically start in February–March in the low-latitude (~30°) Northern Hemisphere and last for ~6–7 months, get progressively later (April–May) and shorter (3–4 months) moving poleward. A similar pattern is observed in the Southern Hemisphere, where blooms that generally begin around August–September in the lower latitudes and which last for ~8 months get later and shorter with increasing latitude. It has previously been considered that phytoplankton blooms consist of a sequential succession of blooms of individual phytoplankton types. Comparison of PIC and chlorophyll peak dates suggests instead that in many open ocean regions, blooms of Coccolithophores and other phytoplankton can co-occur, conflicting with the traditional view of species succession that is thought to take place in temperate regions such as the North Atlantic.
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Coccolithophore calcification response to past ocean acidification and climate change
2014Co-Authors: Sarah A Odea, Samantha J Gibbs, Alex J Poulton, Jeremy R Young, Paul R Bown, Cherry Newsam, Paul A WilsonAbstract:Anthropogenic carbon dioxide emissions are forcing rapid ocean chemistry changes and causing ocean acidification (OA), which is of particular significance for calcifying organisms, including planktonic Coccolithophores. Detailed analysis of Coccolithophore skeletons enables comparison of calcite production in modern and fossil cells in order to investigate biomineralization response of ancient Coccolithophores to climate change. Here we show that the two dominant Coccolithophore taxa across the Paleocene–Eocene Thermal Maximum (PETM) OA global warming event (~56 million years ago) exhibited morphological response to environmental change and both showed reduced calcification rates. However, only Coccolithus pelagicus exhibits a transient thinning of coccoliths, immediately before the PETM, that may have been OA-induced. Changing coccolith thickness may affect calcite production more significantly in the dominant modern species Emiliania huxleyi, but, overall, these PETM records indicate that the environmental factors that govern taxonomic composition and growth rate will most strongly influence Coccolithophore calcification response to anthropogenic change.
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surface biological chemical and optical properties of the patagonian shelf Coccolithophore bloom the brightest waters of the great calcite belt
2014Co-Authors: William M Balch, Stuart C Painter, David T Drapeau, Bruce C Bowler, Emily Lyczkowski, Laura C Lubelczyk, Alex J PoultonAbstract:We report surface observations of a mesoscale Coccolithophore bloom at the shelf break of the Patagonian Shelf during December 2008, representing the densest Coccolithophore population in the Southern Ocean. The bloom was most intense within the Falklands Current, northeast of the Falkland Islands. Emiliania huxleyi dominated bloom waters, with a mixed E. huxleyi and Prorocentrum sp. dinoflagellate bloom to the west and mixed assemblage of diatoms, dinoflagellates, and flagellates to the east. Optical measurements of coccolith light scattering, analytical measurements of their calcite, and microscopic counts all showed this to be an intense Coccolithophore bloom. Average particulate inorganic carbon per coccolith in the bloom was low, typical of the B coccolith morphotype and in agreement with independent measurements made by scanning electron microscopy. Highest particulate inorganic carbon (measured optically and chemically) was observed when residual nitrate (defined as the difference, [NO { ] 2 [Si(OH)4]) was 10–17 mmol L21 and nitrate to phosphate ratios were close to Redfield values. Elevated particle backscattering was observed in the E. huxleyi bloom, whereas the highest particle scattering occurred in the adjoining Prorocentrum sp. bloom. Backscattering from Coccolithophores represented up to 50% of the total backscattering (from organic and inorganic particles) along the main axis of the E. huxleyi bloom. Chlorophyll-specific absorption in the Coccolithophore bloom was typical of marine phytoplankton. Residual nitrate plotted vs. temperature showed that the E. huxleyi bloom was associated with waters between 5uC and 15uC, with depleted silicate. Results suggest that previous drawdown of silicate by diatoms occurred prior to the densest E. huxleyi blooms over the Patagonian Shelf. We speculate that such conditions might also be important for annual development of the broader Great Calcite Belt and other Coccolithophore blooms.
G. Neukermans - One of the best experts on this subject based on the ideXlab platform.
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Detection of Coccolithophore Blooms With BioGeoChemical‐Argo Floats
2020Co-Authors: L. Terrats, H. Claustre, M. Cornec, Alain Mangin, G. NeukermansAbstract:Coccolithophores (calcifying phytoplankton) form extensive blooms in temperate and subpolar oceans as evidenced from ocean-color satellites. This study examines the potential to detect Coccolithophore blooms with BioGeoChemical-Argo (BGC-Argo) floats, autonomous ocean profilers equipped with bio-optical and physicochemical sensors. We first matched float data to ocean-color satellite data of calcite concentration to select floats that sampled Coccolithophore blooms. We identified two floats in the Southern Ocean, which measured the particulate beam attenuation coefficient (c p) in addition to two core BGC-Argo variables, Chlorophyll-a concentration ([Chl-a]) and the particle backscattering coefficient (b bp). We show that Coccolithophore blooms can be identified from floats by distinctively high values of (1) the b bp /c p ratio, a proxy for the refractive index of suspended particles, and (2) the b bp /[Chl-a] ratio, measurable by any BGC-Argo float. The latter thus paves the way to global investigations of environmental control of Coccolithophore blooms and their role in carbon export. Plain Language Summary Coccolithophores are a group of phytoplankton that form an armor of calcite plates. Coccolithophores may form intense blooms which can be identified from space by so-called ocean-color satellites, providing global images of the color of the surface ocean. BioGeoChemical-Argo (BGC-Argo) floats, robots profiling down to 2,000 m with a variety of physicochemical and bio-optical sensors, present an increasingly attractive and cost-effective platform to study phytoplankton blooms and their impact on oceanic biogeochemical cycles. We show that Coccolithophore blooms can be detected by BGC-Argo floats with high confidence, hence providing a new way to study them at the global scale as well as their role in sinking carbon.
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detection of Coccolithophore blooms with biogeochemical argo floats
2020Co-Authors: L. Terrats, H. Claustre, M. Cornec, Alain Mangin, G. NeukermansAbstract:Coccolithophores (calcifying phytoplankton) form extensive blooms in temperate and subpolar oceans as evidenced from ocean-color satellites. This study examines the potential to detect Coccolithophore blooms with BioGeoChemical-Argo (BGC-Argo) floats, autonomous ocean profilers equipped with bio-optical and physicochemical sensors. We first matched float data to ocean-color satellite data of calcite concentration to select floats that sampled Coccolithophore blooms. We identified two floats in the Southern Ocean, which measured the particulate beam attenuation coefficient (c p) in addition to two core BGC-Argo variables, Chlorophyll-a concentration ([Chl-a]) and the particle backscattering coefficient (b bp). We show that Coccolithophore blooms can be identified from floats by distinctively high values of (1) the b bp /c p ratio, a proxy for the refractive index of suspended particles, and (2) the b bp /[Chl-a] ratio, measurable by any BGC-Argo float. The latter thus paves the way to global investigations of environmental control of Coccolithophore blooms and their role in carbon export. Plain Language Summary Coccolithophores are a group of phytoplankton that form an armor of calcite plates. Coccolithophores may form intense blooms which can be identified from space by so-called ocean-color satellites, providing global images of the color of the surface ocean. BioGeoChemical-Argo (BGC-Argo) floats, robots profiling down to 2,000 m with a variety of physicochemical and bio-optical sensors, present an increasingly attractive and cost-effective platform to study phytoplankton blooms and their impact on oceanic biogeochemical cycles. We show that Coccolithophore blooms can be detected by BGC-Argo floats with high confidence, hence providing a new way to study them at the global scale as well as their role in sinking carbon.
Rosalind E M Rickaby - One of the best experts on this subject based on the ideXlab platform.
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poleward expansion of the Coccolithophore emiliania huxleyi
2014Co-Authors: Amos Winter, Jorijntje Henderiks, Rosalind E M Rickaby, Luc Beaufort, Chris W BrownAbstract:Coccolithophores are one of the most abundant eukaryotic phytoplankton in the oceans and are distinguished by their ability to build calcitic platelets (coccoliths). Of the numerous species, Emiliania huxleyi is considered one of the major calcifiers in the pelagic ocean. There is growing concern that increasing levels of CO2 in the atmosphere and the subsequent acidification of the ocean may disrupt the production of coccoliths. Furthermore, any change in the global distribution and abundance of E. huxleyi relative to non-calcifying groups of phytoplankton (e. g. diatoms) will have important effects on the biogeochemical cycling of carbon and climatic feedbacks. We review different lines of evidence that suggest E. huxleyi is increasingly expanding its range into the polar oceans. These observations contribute to the debate on the climatic effects on natural Coccolithophore populations. We postulate that E. huxleyi may be more sensitive to recent environmental changes such as increasing sea surface temperature and salinity than to changing ocean carbonate chemistry, partly because increased availability of CO2(aq) likely alleviates a carbon limitation for the inefficient Rubisco enzyme in these algae. Any potentially important climatic feedbacks of Coccolithophores need a better knowledge of the mechanisms and rates of adaptation by natural populations. As more data and modelling work become available, the real significance of this poleward expansion will become clear.
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controls on stable strontium isotope fractionation in Coccolithophores with implications for the marine sr cycle
2014Co-Authors: Emily I Stevenson, Rosalind E M Rickaby, Michael Hermoso, Jonathan J Tyler, Fabrice Minoletti, Ian J Parkinson, Fatima Mokadem, K W BurtonAbstract:Abstract The controls on stable Sr isotope fractionation into the calcite produced by the Coccolithophore species Emiliania huxleyi , Coccolithus pelagicus spp. braarudii and Gephyrocapsa oceanica are investigated . Each species has been cultured under controlled laboratory conditions at a range of temperatures (10–25 °C) to test the potential of δ 88/86 Sr as a proxy for growth rate and/or sea surface temperature. Coccolithophores are one of the most abundant pelagic calcifiers; since Sr substitutes to some degree for Ca in their calcite coccoliths, Coccolithophores represent a significant output of Sr from seawater, potentially influencing the δ 88/86 Sr mass balance in the modern oceans. The coccoliths are investigated for their δ 88/86 Sr, Sr/Ca, and δ 18 O measured as function of temperature. As temperature is increased all species show a negative stable Sr isotopic fractionation, related to a temperature controlled growth rate. We infer the shift of δ 88/86 Sr to lighter values as indicative of a kinetic control on the isotope fractionation, revealing the potential of δ 88/86 Sr as a proxy for growth rate, which in these experiments is primarily dictated by temperature. The results from these experiments indicate that Coccolithophore calcite incorporates Sr with a very light δ 88/86 Sr isotope composition as low as ∼0‰.
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interaction of the Coccolithophore gephyrocapsa oceanica with its carbon environment response to a recreated high co2 geological past
2012Co-Authors: Adam Moolna, Rosalind E M RickabyAbstract:Coccolithophores have played a key role in the carbon cycle since becoming dominant in the Cretaceous ocean, and their influence depends fundamentally on how they interact with their external carbon environment. Because the photosynthetic carbon-fixing enzyme Rubisco requires high levels of CO(2) for effective catalysis, Coccolithophores are known to induce carbon concentrating mechanisms (CCMs) to raise the level of dissolved inorganic carbon (DIC) in an 'internal pool'. The ocean carbon system has varied greatly over the geological past, suggesting that Coccolithophore interactions with that external carbon environment will have changed in parallel. The widespread present-day Coccolithophore Gephyrocapsa oceanica was acclimated here to a geological scale change in the seawater carbon system (five times higher DIC and alkalinity). Significant acclimation in response to the external carbon environment was demonstrated by a fourfold increase in the K(m) substrate concentration requirement for half-maximum photosynthetic carbon fixation rates (suggesting that CCMs were down-regulated when ambient carbon was more available). There was, however, no difference in growth rate, morphology or calcification, suggesting that calcification is not coupled to photosynthesis as one of the CCMs induced here and that productivity (growth rate and calcification) is not carbon-limited under representative present-day conditions. Beyond the kinetic parameters of photosynthesis, the only other indication of changed cell physiology seen was the increased fractionation of carbon isotopes into organic matter. These findings demonstrate that G. oceanica changes its carbon-use physiology to maintain consistent photosynthetic carbon fixation in concert with different levels of ambient DIC without changing its morphology or calcification.
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perturbing phytoplankton response and isotopic fractionation with changing carbonate chemistry in two Coccolithophore species
2010Co-Authors: Rosalind E M Rickaby, Jorijntje Henderiks, Jodi N YoungAbstract:Abstract. All species of Coccolithophore appear to respond to perturbations of carbonate chemistry in a different way. Here, we show that the degree of malformation, growth rate and stable isotopic composition of organic matter and carbonate produced by two contrasting species of Coccolithophore (Gephyrocapsa oceanica and Coccolithus pelagicus ssp. braarudii) are indicative of differences between their photosynthetic and calcification response to changing DIC levels (ranging from ~1100 to ~7800 μmol kg−1) at constant pH (8.13 ± 0.02). Gephyrocapsa oceanica thrived under all conditions of DIC, showing evidence of increased growth rates at higher DIC, but C. braarudii was detrimentally affected at high DIC showing signs of malformation, and decreased growth rates. The carbon isotopic fractionation into organic matter and the coccoliths suggests that C. braarudii utilises a common internal pool of carbon for calcification and photosynthesis but G. oceanica relies on independent supplies for each process. All Coccolithophores appear to utilize bicarbonate as their ultimate source of carbon for calcification resulting in the release of a proton. But, we suggest that this proton can be harnessed to enhance the supply of CO2(aq) for photosynthesis either from a large internal HCO3- pool which acts as a pH buffer (C. braarudii), or pumped externally to aid the diffusive supply of CO2 across the membrane from the abundant HCO3- (G. oceanica), likely mediated by an internal and external carbonic anhydrase respectively. Our simplified hypothetical spectrum of physiologies may provide a context to understand different species response to changing pH and DIC, the species-specific ep and calcite "vital effects", as well as accounting for geological trends in Coccolithophore cell size.
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Phytoplankton calcification in a high-CO2 world
2008Co-Authors: M. Debora Iglesias-rodriguez, Paul R. Halloran, John R. Gittins, Ian R Hall, Samantha J Gibbs, Darryl R H Green, Toby Tyrrell, Elena Colmenero-hidalgo, Rosalind E M Rickaby, Peter Von DassowAbstract:Ocean acidification in response to rising atmospheric CO2 partial pressures is widely expected to reduce calcification by marine organisms. From the mid-Mesozoic, Coccolithophores have been major calcium carbonate producers in the world's oceans, today accounting for about a third of the total marine CaCO3 production. Here, we present laboratory evidence that calcification and net primary production in the Coccolithophore species Emiliania huxleyi are significantly increased by high CO2 partial pressures. Field evidence from the deep ocean is consistent with these laboratory conclusions, indicating that over the past 220 years there has been a 40% increase in average coccolith mass. Our findings show that Coccolithophores are already responding and will probably continue to respond to rising atmospheric CO2 partial pressures, which has important implications for biogeochemical modeling of future oceans and climate