33 results on '"Richier S"'
Search Results
2. OXIDATIVE STRESS RESISTANCE IN Anemonia viridis: P15-188
- Author
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Plantivaux, A., Furla, P., Richier, S., Garello, G., Merle, P.-L., and Allemand, D.
- Published
- 2004
3. Geographical CO2 sensitivity of phytoplankton correlates with ocean buffer capacity
- Author
-
Richier, S, Achterberg, EP, Humphreys, MP, Poulton, A, Suggett, DJ, Tyrrell, T, and Moore, CM
- Subjects
Ecology ,Geography ,Climate ,Acclimatization ,Oceans and Seas ,fungi ,Phytoplankton ,Carbonates ,Seawater ,Carbon Dioxide - Abstract
© 2018 John Wiley & Sons Ltd Accumulation of anthropogenic CO2 is significantly altering ocean chemistry. A range of biological impacts resulting from this oceanic CO2 accumulation are emerging, however, the mechanisms responsible for observed differential susceptibility between organisms and across environmental settings remain obscure. A primary consequence of increased oceanic CO2 uptake is a decrease in the carbonate system buffer capacity, which characterizes the system's chemical resilience to changes in CO2, generating the potential for enhanced variability in pCO2 and the concentration of carbonate [(Formula presented.)], bicarbonate [(Formula presented.)], and protons [H+] in the future ocean. We conducted a meta-analysis of 17 shipboard manipulation experiments performed across three distinct geographical regions that encompassed a wide range of environmental conditions from European temperate seas to Arctic and Southern oceans. These data demonstrated a correlation between the magnitude of natural phytoplankton community biological responses to short-term CO2 changes and variability in the local buffer capacity across ocean basin scales. Specifically, short-term suppression of small phytoplankton (
- Published
- 2018
4. Carbon cycling and phytoplankton responses within highly-replicated shipboard carbonate chemistry manipulation experiments conducted around Northwest European Shelf Seas
- Author
-
Richier S, Achterberg EP, Dumousseaud C, Poulton AJ, Suggett DJ, Tyrrell T, Zubkov MV, and Moore CM
- Subjects
Meteorology & Atmospheric Sciences ,0499 Other Earth Sciences, 0601 Biochemistry and Cell Biology - Abstract
The ongoing oceanic uptake of anthropogenic carbon dioxide (CO2) is significantly altering the carbonate chemistry of seawater, a phenomenon referred to as ocean acidification. Experimental manipulations have been increasingly used to gauge how continued ocean acidification will potentially impact marine ecosystems and their associated biogeochemical cycles in the future; however, results amongst studies, particularly when performed on natural communities, are highly variable, which in part likely reflects inconsistencies in experimental approach. To investigate the potential for identification of more generic responses and greater experimentally reproducibility, we devised and implemented a series of highly replicated (n = 8), short term (2–4 days) multi-level (≥ 4 conditions) carbonate chemistry/nutrient manipulation experiments on a range of natural microbial communities sampled in Northwest European shelf seas. Carbonate chemistry manipulations and resulting biological responses were found to be highly reproducible within individual experiments and to a lesser extent between geographically different experiments. Statistically robust reproducible physiological responses of phytoplankton to increasing pCO2, characterized by a suppression of net growth for small sized cells (< 10 μm), were observed in the majority of the experiments, irrespective of nutrient status. Remaining between-experiment variability was potentially linked to initial community structure and/or other site-specific environmental factors. Analysis of carbon cycling within the experiments revealed the expected increased sensitivity of carbonate chemistry to biological processes at higher pCO2 and hence lower buffer capacity. The results thus emphasize how biological-chemical feedbacks may be altered in the future ocean.
- Published
- 2014
5. Cnidarian-Dinoflagellate symbiosis-mediated adaptation to environmental stress
- Author
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Richier, S., Sabourault, Cécile, Ferrier-Pages, C., Merle, Pierre-Laurent, Furla, Paola, Allemand, Denis, Systématique, adaptation, évolution (SAE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), and Leballeur, Philippe
- Subjects
[SDV.BBM] Life Sciences [q-bio]/Biochemistry, Molecular Biology ,[SDV.BBM]Life Sciences [q-bio]/Biochemistry, Molecular Biology - Published
- 2011
6. Phytoplankton responses and associated carbon cycling during shipboard carbonate chemistry manipulation experiments conducted around Northwest European shelf seas
- Author
-
Richier, S., Achterberg, E.P., Dumousseaud, C., Poulton, A.J., Suggett, D.J., Tyrrell, T., Zubkov, M.V., Moore, C.M., Richier, S., Achterberg, E.P., Dumousseaud, C., Poulton, A.J., Suggett, D.J., Tyrrell, T., Zubkov, M.V., and Moore, C.M.
- Abstract
The ongoing oceanic uptake of anthropogenic carbon dioxide (CO2) is significantly altering the carbonate chemistry of seawater, a phenomenon referred to as ocean acidification. Experimental manipulations have been increasingly used to gauge how continued ocean acidification will potentially impact marine ecosystems and their associated biogeochemical cycles in the future; however, results amongst studies, particularly when performed on natural communities, are highly variable, which in part likely reflects inconsistencies in experimental approach. To investigate the potential for identification of more generic responses and greater experimentally reproducibility, we devised and implemented a series of highly replicated (n = 8), short term (2–4 days) multi-level (≥ 4 conditions) carbonate chemistry/nutrient manipulation experiments on a range of natural microbial communities sampled in Northwest European shelf seas. Carbonate chemistry manipulations and resulting biological responses were found to be highly reproducible within individual experiments and to a lesser extent between geographically different experiments. Statistically robust reproducible physiological responses of phytoplankton to increasing pCO2, characterized by a suppression of net growth for small sized cells (< 10 μm), were observed in the majority of the experiments, irrespective of nutrient status. Remaining between-experiment variability was potentially linked to initial community structure and/or other site-specific environmental factors. Analysis of carbon cycling within the experiments revealed the expected increased sensitivity of carbonate chemistry to biological processes at higher pCO2 and hence lower buffer capacity. The results thus emphasize how biological-chemical feedbacks may be altered in the future ocean.
- Published
- 2014
7. Coccolithophores on the North-West European Shelf: calcification rates and environmental controls
- Author
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Poulton, A.J., Stinchcombe, M.C., Achterberg, E.P., Bakker, D.C.E., Dumousseaud, C., Lawson, H.E., Lee, G.A., Richier, S., Sugget, D.J., Young, J.R., Poulton, A.J., Stinchcombe, M.C., Achterberg, E.P., Bakker, D.C.E., Dumousseaud, C., Lawson, H.E., Lee, G.A., Richier, S., Sugget, D.J., and Young, J.R.
- Abstract
Coccolithophores are a key functional group in terms of the pelagic production of calcium carbonate (calcite), although their contribution to shelf sea biogeochemistry, and how this relates to environmental conditions, is poorly constrained. Measurements of calcite production (CP) and coccolithophore abundance were made on the north-west European shelf to examine trends in coccolithophore calcification along natural gradients of carbonate chemistry, macronutrient availability and plankton composition. Similar measurements were also made in three bioassay experiments where nutrient (nitrate, phosphate) and pCO2 levels were manipulated. Nanoflagellates (< 10 μm) dominated chlorophyll biomass and primary production (PP) at all but one sampling site, with CP ranging from 0.6 to 9.6 mmol C m−2 d−1. High CP and coccolithophore abundance occurred in a diatom bloom in fully mixed waters off Heligoland, but not in two distinct coccolithophore blooms in the central North Sea and Western English Channel. Coccolithophore abundance and CP showed no correlation with nutrient concentrations or ratios, while significant (p < 0.01) correlations between CP, cell-specific calcification (cell-CF) and irradiance in the water column highlighted how light availability exerts a strong control on pelagic CP. In the experimental bioassays, Emiliania-huxleyi-dominated coccolithophore communities in shelf waters (northern North Sea, Norwegian Trench) showed a strong response in terms of CP to combined nitrate and phosphate addition, mediated by changes in cell-CF and growth rates. In contrast, an offshore diverse coccolithophore community (Bay of Biscay) showed no response to nutrient addition, while light availability or mortality may have been more important in controlling this community. Sharp decreases in pH and a rough halving of calcite saturation states in the bioassay experiments led to decreased CP in the Bay of Biscay and northern North Sea, but not the Norwegian Trench. These decrea
- Published
- 2014
8. Hihly efficient carbon export pump in a monispecific bloom of Phaeocystis in the Arctic ocean
- Author
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Le Moigne, Frederic A. C., Poulton, A., Daniels, C., Fragroso, G., Richier, S., Henson, S., Le Moigne, Frederic A. C., Poulton, A., Daniels, C., Fragroso, G., Richier, S., and Henson, S.
- Published
- 2014
9. Effect of enhanced pCO2 levels on the production of dissolved organic carbon and transparent exopolymer particles in short-term bioassay experiments
- Author
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MacGilchrist, G. A., Shi, T., Tyrrell, T., Richier, S., Moore, C. M., Dumousseaud, C., Achterberg, Eric P., MacGilchrist, G. A., Shi, T., Tyrrell, T., Richier, S., Moore, C. M., Dumousseaud, C., and Achterberg, Eric P.
- Abstract
It has been proposed that increasing levels of pCO(2) in the surface ocean will lead to more partitioning of the organic carbon fixed by marine primary production into the dissolved rather than the particulate fraction. This process may result in enhanced accumulation of dissolved organic carbon (DOC) in the surface ocean and/or concurrent accumulation of transparent exopolymer particles (TEPs), with important implications for the functioning of the marine carbon cycle. We investigated this in shipboard bioassay experiments that considered the effect of four different pCO(2) scenarios (ambient, 550, 750 and 1000 mu atm) on unamended natural phytoplankton communities from a range of locations in the northwest European shelf seas. The environmental settings, in terms of nutrient availability, phytoplankton community structure and growth conditions, varied considerably between locations. We did not observe any strong or consistent effect of pCO(2) on DOC production. There was a significant but highly variable effect of pCO(2) on the production of TEPs. In three of the five experiments, variation of TEP production between pCO(2) treatments was caused by the effect of pCO(2) on phytoplankton growth rather than a direct effect on TEP production. In one of the five experiments, there was evidence of enhanced TEP production at high pCO(2) (twice as much production over the 96 h incubation period in the 750 mu atm treatment compared with the ambient treatment) independent of indirect effects, as hypothesised by previous studies. Our results suggest that the environmental setting of experiments (community structure, nutrient availability and occurrence of phytoplankton growth) is a key factor determining the TEP response to pCO(2) perturbations.
- Published
- 2014
- Full Text
- View/download PDF
10. Coccolithophores on the north-west European shelf: Calcification rates and environmental controls
- Author
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Poulton, AJ, Stinchcombe, MC, Achterberg, EP, Bakker, DCE, Dumousseaud, C, Lawson, HE, Lee, GA, Richier, S, Suggett, DJ, Young, JR, Poulton, AJ, Stinchcombe, MC, Achterberg, EP, Bakker, DCE, Dumousseaud, C, Lawson, HE, Lee, GA, Richier, S, Suggett, DJ, and Young, JR
- Abstract
Coccolithophores are a key functional group in terms of the pelagic production of calcium carbonate (calcite), although their contribution to shelf sea biogeochemistry, and how this relates to environmental conditions, is poorly constrained. Measurements of calcite production (CP) and coccolithophore abundance were made on the north-west European shelf to examine trends in coccolithophore calcification along natural gradients of carbonate chemistry, macronutrient availability and plankton composition. Similar measurements were also made in three bioassay experiments where nutrient (nitrate, phosphate) and pCO2 levels were manipulated. Nanoflagellates (< 10) dominated chlorophyll biomass and primary production (PP) at all but one sampling site, with CP ranging from 0.6 to 9.6 mmol Cm-2 d-1. High CP and coccolithophore abundance occurred in a diatom bloom in fully mixed waters off Heligoland, but not in two distinct coccolithophore blooms in the central North Sea and Western English Channel. Coccolithophore abundance and CP showed no correlation with nutrient concentrations or ratios, while significant (p < 0.01) correlations between CP, cell-specific calcification (cell-CF) and irradiance in the water column highlighted how light availability exerts a strong control on pelagic CP. In the experimental bioassays,Emiliania-huxleyi-dominated coccolithophore communities in shelf waters (northern North Sea, Norwegian Trench) showed a strong response in terms of CP to combined nitrate and phosphate addition, mediated by changes in cell-CF and growth rates. In contrast, an offshore diverse coccolithophore community (Bay of Biscay) showed no response to nutrient addition, while light availability or mortality may have been more important in controlling this community. Sharp decreases in pH and a rough halving of calcite saturation states in the bioassay experiments led to decreased CP in the Bay of Biscay and northern North Sea, but not the Norwegian Trench. These decreases i
- Published
- 2014
11. Phytoplankton responses and associated carbon cycling during shipboard carbonate chemistry manipulation experiments conducted around Northwest European shelf seas
- Author
-
Richier, S., primary, Achterberg, E. P., additional, Dumousseaud, C., additional, Poulton, A. J., additional, Suggett, D. J., additional, Tyrrell, T., additional, Zubkov, M. V., additional, and Moore, C. M., additional
- Published
- 2014
- Full Text
- View/download PDF
12. Coccolithophores on the north-west European shelf: calcification rates and environmental controls
- Author
-
Poulton, A. J., primary, Stinchcombe, M. C., additional, Achterberg, E. P., additional, Bakker, D. C. E., additional, Dumousseaud, C., additional, Lawson, H. E., additional, Lee, G. A., additional, Richier, S., additional, Suggett, D. J., additional, and Young, J. R., additional
- Published
- 2014
- Full Text
- View/download PDF
13. Effect of enhanced <i>p</i>CO<sub>2</sub> levels on the production of dissolved organic carbon and transparent exopolymer particles in short-term bioassay experiments
- Author
-
MacGilchrist, G. A., primary, Shi, T., additional, Tyrrell, T., additional, Richier, S., additional, Moore, C. M., additional, Dumousseaud, C., additional, and Achterberg, E. P., additional
- Published
- 2014
- Full Text
- View/download PDF
14. Effect of enhanced pCO2 levels on the production of DOC and TEP in short-term bioassay experiments
- Author
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MacGilchrist, G. A., primary, Shi, T., additional, Tyrrell, T., additional, Richier, S., additional, Moore, C. M., additional, Dumousseaud, C., additional, and Achterberg, E. P., additional
- Published
- 2014
- Full Text
- View/download PDF
15. Carbon cycling and phytoplankton responses within highly-replicated shipboard carbonate chemistry manipulation experiments conducted around Northwest European Shelf Seas
- Author
-
Richier, S., primary, Achterberg, E. P., additional, Dumousseaud, C., additional, Poulton, A. J., additional, Suggett, D. J., additional, Tyrrell, T., additional, Zubkov, M. V., additional, and Moore, C. M., additional
- Published
- 2014
- Full Text
- View/download PDF
16. Pan genome of the phytoplankton Emiliania underpins its global distribution
- Author
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Read, B. A., Kegel, J., Klute, M. J., Kuo, A., Lefebvre, S. C., Maumus, F., Mayer, C., Miller, J., Monier, A., Salamov, A., Young, J., Aguilar, M., Claverie, J.-M., Frickenhaus, S., Gonzalez, K., Herman, E. K., Lin, Y.-C., Napier, J., Ogata, H., Sarno, A. F., Shmutz, J., Schroeder, D., De Vargas, C., Verret, F., Von Dassow, P., Valentin, K., Van De Peer, Y., Wheeler, G., Dacks, J. B., Delwiche, C. F., Dyhrman, S. T., Glöckner, G., John, U., Richards, T., Worden, Alexandra Z., Zhang, X., Grigoriev, I. V., Allen, A. E., Bidle, K., Borodovsky, M., Bowler, C., Brownlee, C., Mark Cock, J., Elias, M., Gladyshev, V. N., Groth, M., Guda, C., Hadaegh, A., Iglesias-Rodriguez, M. D., Jenkins, J., Jones, B. M., Lawson, T., Leese, F., Lindquist, E., Lobanov, A., Lomsadze, A., Malik, S.-B., Marsh, M. E., MacKinder, L., Mock, T., Mueller-Roeber, B., Pagarete, A., Parker, M., Probert, I., Quesneville, H., Raines, C., Rensing, S. A., Riaño-Pachón, D. M., Richier, S., Rokitta, S., Shiraiwa, Y., Soanes, D. M., Van Der Giezen, M., Wahlund, T. M., Williams, B., Wilson, W., Wolfe, G., Wurch, L. L., Read, B. A., Kegel, J., Klute, M. J., Kuo, A., Lefebvre, S. C., Maumus, F., Mayer, C., Miller, J., Monier, A., Salamov, A., Young, J., Aguilar, M., Claverie, J.-M., Frickenhaus, S., Gonzalez, K., Herman, E. K., Lin, Y.-C., Napier, J., Ogata, H., Sarno, A. F., Shmutz, J., Schroeder, D., De Vargas, C., Verret, F., Von Dassow, P., Valentin, K., Van De Peer, Y., Wheeler, G., Dacks, J. B., Delwiche, C. F., Dyhrman, S. T., Glöckner, G., John, U., Richards, T., Worden, Alexandra Z., Zhang, X., Grigoriev, I. V., Allen, A. E., Bidle, K., Borodovsky, M., Bowler, C., Brownlee, C., Mark Cock, J., Elias, M., Gladyshev, V. N., Groth, M., Guda, C., Hadaegh, A., Iglesias-Rodriguez, M. D., Jenkins, J., Jones, B. M., Lawson, T., Leese, F., Lindquist, E., Lobanov, A., Lomsadze, A., Malik, S.-B., Marsh, M. E., MacKinder, L., Mock, T., Mueller-Roeber, B., Pagarete, A., Parker, M., Probert, I., Quesneville, H., Raines, C., Rensing, S. A., Riaño-Pachón, D. M., Richier, S., Rokitta, S., Shiraiwa, Y., Soanes, D. M., Van Der Giezen, M., Wahlund, T. M., Williams, B., Wilson, W., Wolfe, G., and Wurch, L. L.
- Abstract
Coccolithophores have influenced the global climate for over 200 million years. These marine phytoplankton can account for 20 per cent of total carbon fixation in some systems. They form blooms that can occupy hundreds of thousands of square kilometres and are distinguished by their elegantly sculpted calcium carbonate exoskeletons (coccoliths), rendering them visible from space. Although coccolithophores export carbon in the form of organic matter and calcite to the sea floor, they also release CO 2 in the calcification process. Hence, they have a complex influence on the carbon cycle, driving either CO 2 production or uptake, sequestration and export to the deep ocean. Here we report the first haptophyte reference genome, from the coccolithophore Emiliania huxleyi strain CCMP1516, and sequences from 13 additional isolates. Our analyses reveal a pan genome (core genes plus genes distributed variably between strains) probably supported by an atypical complement of repetitive sequence in the genome. Comparisons across strains demonstrate that E. huxleyi, which has long been considered a single species, harbours extensive genome variability reflected in different metabolic repertoires. Genome variability within this species complex seems to underpin its capacity both to thrive in habitats ranging from the equator to the subarctic and to form large-scale episodic blooms under a wide variety of environmental conditions. © 2013 Macmillan Publishers Limited. All rights reserved.
- Published
- 2013
- Full Text
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17. Response of the calcifying coccolithophore Emiliania huxleyi to low pH/high pCO2: from physiology to molecular level
- Author
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Richier, S., Fiorini, S., Kerros, M.E., von Dassow, P., Gattuso, J.P., Richier, S., Fiorini, S., Kerros, M.E., von Dassow, P., and Gattuso, J.P.
- Abstract
The emergence of ocean acidification as a significant threat to calcifying organisms in marine ecosystems creates a pressing need to understand the physiological and molecular mechanisms by which calcification is affected by environmental parameters. We report here, for the first time, changes in gene expression induced by variations in pH/pCO2 in the widespread and abundant coccolithophore Emiliania huxleyi. Batch cultures were subjected to increased partial pressure of CO2 (pCO2; i.e. decreased pH), and the changes in expression of four functional gene classes directly or indirectly related to calcification were investigated. Increased pCO2 did not affect the calcification rate and only carbonic anhydrase transcripts exhibited a significant down-regulation. Our observation that elevated pCO2 induces only limited changes in the transcription of several transporters of calcium and bicarbonate gives new significant elements to understand cellular mechanisms underlying the early response of E. huxleyi to CO2-driven ocean acidification., The emergence of ocean acidification as a significant threat to calcifying organisms in marine ecosystems creates a pressing need to understand the physiological and molecular mechanisms by which calcification is affected by environmental parameters. We report here, for the first time, changes in gene expression induced by variations in pH/pCO2 in the widespread and abundant coccolithophore Emiliania huxleyi. Batch cultures were subjected to increased partial pressure of CO2 (pCO2; i.e. decreased pH), and the changes in expression of four functional gene classes directly or indirectly related to calcification were investigated. Increased pCO2 did not affect the calcification rate and only carbonic anhydrase transcripts exhibited a significant down-regulation. Our observation that elevated pCO2 induces only limited changes in the transcription of several transporters of calcium and bicarbonate gives new significant elements to understand cellular mechanisms underlying the early response of E. huxleyi to CO2-driven ocean acidification.
- Published
- 2011
18. Early development and molecular plasticity in the Mediterranean sea urchin Paracentrotus lividus exposed to CO2-driven acidification
- Author
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Martin, S, Richier, S, Pedrotti, M-L, Dupont, S, Castejon, C, Gerakis, Y, Kerros, M-E, Oberhaensli, F, Teyssie, J-L, Jeffree, R, Gattuso, J-P, Martin, S, Richier, S, Pedrotti, M-L, Dupont, S, Castejon, C, Gerakis, Y, Kerros, M-E, Oberhaensli, F, Teyssie, J-L, Jeffree, R, and Gattuso, J-P
- Published
- 2011
19. Corrigendum to "Multi-year renewal of green tides: 18 years of algal mat monitoring (2003-2020) on French coastline (Brittany region)".
- Author
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Louis J, Ballu S, Rossi N, Lasbleiz M, Perrot T, Daniel C, Cellier L, Hénaff F, and Richier S
- Published
- 2023
- Full Text
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20. Multi-year renewal of green tides: 18 years of algal mat monitoring (2003-2020) on French coastline (Brittany region).
- Author
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Louis J, Ballu S, Rossi N, Lasbleiz M, Perrot T, Daniel C, Cellier L, Hénaff F, and Richier S
- Subjects
- France, Water Pollution statistics & numerical data, Ulva, Seasons, Eutrophication, Environmental Monitoring
- Abstract
To better understand the green tide phenomenon impacting French coastline and give guidance to stakeholders to elaborate effective mitigation plan, an extensive survey has been deployed on Brittany hot spots. Based on 18 years monitoring database, the objectives of this work were to investigate the inter-and-intra annual evolutions of Ulva beaching, and to assess the parameters driving green tide annual renewal. The yearly cumulated area of Ulva mat on the Brittany coast averaged 2,42 ± 0,84 ha, of which 55 ± 12 % % was reported within Saint Brieuc-Binic Bay, with a maximal beaching generally observed in July. The renewal of green tide at spring time seems to be correlated with the Ulva bloom from the previous autumn period, particularly in bays with low exposure to swell. The residual stock, defined as Ulva fragments maintained in healthy conditions during the winter season, appears as highly dependent on nitrogen summer flows., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Sophie Richier reports financial support was provided by Brittany Region. Sophie Richier reports financial support was provided by department councils of Finistère, Morbihan, Côtes d'Armor and Ile et Vilaine. Sophie Richier reports financial support was provided by Regional water agency of Loire-Brittany. Sophie Richier reports financial support was provided by IFREMER., (Copyright © 2023 Elsevier Ltd. All rights reserved.)
- Published
- 2023
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21. Geographical CO 2 sensitivity of phytoplankton correlates with ocean buffer capacity.
- Author
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Richier S, Achterberg EP, Humphreys MP, Poulton AJ, Suggett DJ, Tyrrell T, and Moore CM
- Subjects
- Acclimatization, Carbonates, Geography, Oceans and Seas, Carbon Dioxide analysis, Climate, Phytoplankton physiology, Seawater chemistry
- Abstract
Accumulation of anthropogenic CO
2 is significantly altering ocean chemistry. A range of biological impacts resulting from this oceanic CO2 accumulation are emerging, however, the mechanisms responsible for observed differential susceptibility between organisms and across environmental settings remain obscure. A primary consequence of increased oceanic CO2 uptake is a decrease in the carbonate system buffer capacity, which characterizes the system's chemical resilience to changes in CO2 , generating the potential for enhanced variability in pCO2 and the concentration of carbonate [ CO 3 2 - ], bicarbonate [ HCO 3 - ], and protons [H+ ] in the future ocean. We conducted a meta-analysis of 17 shipboard manipulation experiments performed across three distinct geographical regions that encompassed a wide range of environmental conditions from European temperate seas to Arctic and Southern oceans. These data demonstrated a correlation between the magnitude of natural phytoplankton community biological responses to short-term CO2 changes and variability in the local buffer capacity across ocean basin scales. Specifically, short-term suppression of small phytoplankton (<10 μm) net growth rates were consistently observed under enhanced pCO2 within experiments performed in regions with higher ambient buffer capacity. The results further highlight the relevance of phytoplankton cell size for the impacts of enhanced pCO2 in both the modern and future ocean. Specifically, cell size-related acclimation and adaptation to regional environmental variability, as characterized by buffer capacity, likely influences interactions between primary producers and carbonate chemistry over a range of spatio-temporal scales., (© 2018 John Wiley & Sons Ltd.)- Published
- 2018
- Full Text
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22. Abundances of iron-binding photosynthetic and nitrogen-fixing proteins of Trichodesmium both in culture and in situ from the North Atlantic.
- Author
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Richier S, Macey AI, Pratt NJ, Honey DJ, Moore CM, and Bibby TS
- Subjects
- Acclimatization drug effects, Atlantic Ocean, Chlorophyll metabolism, Cyanobacteria drug effects, Cyanobacteria physiology, Dose-Response Relationship, Drug, Geography, Iron pharmacology, Nitrogen Fixation drug effects, Oxidoreductases metabolism, Photosynthesis drug effects, Photosystem I Protein Complex metabolism, Photosystem II Protein Complex metabolism, Water Microbiology, Bacterial Proteins metabolism, Cyanobacteria metabolism, Iron metabolism, Iron-Binding Proteins metabolism
- Abstract
Marine cyanobacteria of the genus Trichodesmium occur throughout the oligotrophic tropical and subtropical oceans, where they can dominate the diazotrophic community in regions with high inputs of the trace metal iron (Fe). Iron is necessary for the functionality of enzymes involved in the processes of both photosynthesis and nitrogen fixation. We combined laboratory and field-based quantifications of the absolute concentrations of key enzymes involved in both photosynthesis and nitrogen fixation to determine how Trichodesmium allocates resources to these processes. We determined that protein level responses of Trichodesmium to iron-starvation involve down-regulation of the nitrogen fixation apparatus. In contrast, the photosynthetic apparatus is largely maintained, although re-arrangements do occur, including accumulation of the iron-stress-induced chlorophyll-binding protein IsiA. Data from natural populations of Trichodesmium spp. collected in the North Atlantic demonstrated a protein profile similar to iron-starved Trichodesmium in culture, suggestive of acclimation towards a minimal iron requirement even within an oceanic region receiving a high iron-flux. Estimates of cellular metabolic iron requirements are consistent with the availability of this trace metal playing a major role in restricting the biomass and activity of Trichodesmium throughout much of the subtropical ocean.
- Published
- 2012
- Full Text
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23. Early development and molecular plasticity in the Mediterranean sea urchin Paracentrotus lividus exposed to CO2-driven acidification.
- Author
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Martin S, Richier S, Pedrotti ML, Dupont S, Castejon C, Gerakis Y, Kerros ME, Oberhänsli F, Teyssié JL, Jeffree R, and Gattuso JP
- Subjects
- Animals, Calcification, Physiologic, Calcium metabolism, Embryo, Nonmammalian drug effects, Female, Fertilization drug effects, Gene Expression Regulation, Larva cytology, Male, Mediterranean Sea, Oceans and Seas, Carbon Dioxide pharmacology, Hydrogen-Ion Concentration, Larva drug effects, Paracentrotus drug effects, Paracentrotus embryology, Paracentrotus growth & development
- Abstract
Ocean acidification is predicted to have significant effects on benthic calcifying invertebrates, in particular on their early developmental stages. Echinoderm larvae could be particularly vulnerable to decreased pH, with major consequences for adult populations. The objective of this study was to understand how ocean acidification would affect the initial life stages of the sea urchin Paracentrotus lividus, a common species that is widely distributed in the Mediterranean Sea and the NE Atlantic. The effects of decreased pH (elevated P(CO(2))) were investigated through physiological and molecular analyses on both embryonic and larval stages. Eggs and larvae were reared in Mediterranean seawater at six pH levels, i.e. pH(T) 8.1, 7.9, 7.7, 7.5, 7.25 and 7.0. Fertilization success, survival, growth and calcification rates were monitored over a 3 day period. The expression of genes coding for key proteins involved in development and biomineralization was also monitored. Paracentrotus lividus appears to be extremely resistant to low pH, with no effect on fertilization success or larval survival. Larval growth was slowed when exposed to low pH but with no direct impact on relative larval morphology or calcification down to pH(T) 7.25. Consequently, at a given time, larvae exposed to low pH were present at a normal but delayed larval stage. More surprisingly, candidate genes involved in development and biomineralization were upregulated by factors of up to 26 at low pH. Our results revealed plasticity at the gene expression level that allows a normal, but delayed, development under low pH conditions.
- Published
- 2011
- Full Text
- View/download PDF
24. Response of the calcifying coccolithophore Emiliania huxleyi to low pH/high pCO 2 : from physiology to molecular level.
- Author
-
Richier S, Fiorini S, Kerros ME, von Dassow P, and Gattuso JP
- Abstract
The emergence of ocean acidification as a significant threat to calcifying organisms in marine ecosystems creates a pressing need to understand the physiological and molecular mechanisms by which calcification is affected by environmental parameters. We report here, for the first time, changes in gene expression induced by variations in pH/pCO
2 in the widespread and abundant coccolithophore Emiliania huxleyi . Batch cultures were subjected to increased partial pressure of CO2 (pCO2 ; i.e. decreased pH), and the changes in expression of four functional gene classes directly or indirectly related to calcification were investigated. Increased pCO2 did not affect the calcification rate and only carbonic anhydrase transcripts exhibited a significant down-regulation. Our observation that elevated pCO2 induces only limited changes in the transcription of several transporters of calcium and bicarbonate gives new significant elements to understand cellular mechanisms underlying the early response of E. huxleyi to CO2 -driven ocean acidification.- Published
- 2011
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25. Light-dependent transcriptional regulation of genes of biogeochemical interest in the diploid and haploid life cycle stages of Emiliania huxleyi.
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Richier S, Kerros ME, de Vargas C, Haramaty L, Falkowski PG, and Gattuso JP
- Subjects
- Diploidy, Haploidy, Darkness, Eukaryota physiology, Gene Expression Profiling, Light
- Abstract
The expression of genes of biogeochemical interest in calcifying and noncalcifying life stages of the coccolithophore Emiliania huxleyi was investigated. Transcripts potentially involved in calcification were tested through a light-dark cycle. These transcripts were more abundant in calcifying cells and were upregulated in the light. Their application as potential candidates for in situ biogeochemical proxies is also suggested.
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- 2009
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26. Response of the symbiotic cnidarian Anthopleura elegantissima transcriptome to temperature and UV increase.
- Author
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Richier S, Rodriguez-Lanetty M, Schnitzler CE, and Weis VM
- Abstract
Elevated temperature and solar radiation, including ultraviolet radiation, are now recognized as the primary environmental stresses that lead to mass cnidarian bleaching. This study takes a functional genomics approach to identifying genes that change expression soon after exposure to these stressors in the temperate sea anemone Anthopleura elegantissima that harbors Symbiodinium, the same genus of symbionts found in reef-building corals. Symbiotic anemones were subjected to elevated temperature or UV over a 24 h period. cDNA from these animals was hybridized to a 10,000-feature cDNA microarray of A. elegantissima. Overall 2.7% of the 10,000 features were found to be differentially expressed as a function of temperature or UV stress. Of the 86 features sequenced, 45% displayed significant homology to sequences in GenBank. There are 27 features that were differentially expressed in both stress conditions. Gene ontology analysis placed the differentially expressed genes in a wide range of categories including cytoskeleton organization and biogenesis, protein biosynthesis, cell proliferation, apoptosis and transport. This suggests that the early stress response to elevated temperature and UV involves essentially all aspects of host cellular regulation and machinery and that downstream cnidarian bleaching is a complex cellular response in host tissues., (2008 Elsevier Inc. All rights reserved.)
- Published
- 2008
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27. Calcification and associated physiological parameters during a stress event in the scleractinian coral Stylophora pistillata.
- Author
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Moya A, Ferrier-Pagès C, Furla P, Richier S, Tambutté E, Allemand D, and Tambutté S
- Subjects
- Animals, Anthozoa radiation effects, Bone and Bones physiology, Bone and Bones radiation effects, Chlorophyll metabolism, Light, Photosynthesis radiation effects, Photosystem II Protein Complex metabolism, Protein Carbonylation radiation effects, Anthozoa physiology, Calcification, Physiologic radiation effects
- Abstract
High calcification rates observed in reef coral organisms are due to the symbiotic relationship established between scleractinian corals and their photosynthetic dinoflagellates, commonly called zooxanthellae. Zooxanthellae are known to enhance calcification in the light, a process referred as "light-enhanced calcification". The disruption of the relationship between corals and their zooxanthellae leads to bleaching. Bleaching is one of the major causes of the present decline of coral reefs related to climate change and anthropogenic activities. In our aquaria, corals experienced a chemical pollution leading to bleaching and ending with the death of corals. During the time course of this bleaching event, we measured multiple parameters and could evidence four major consecutive steps: 1) at month 1 (January 2005), the stress affected primarily the photosystem II machinery of zooxanthellae resulting in an immediate decrease of photosystem II efficiency, 2) at month 2, the stress affected the photosynthetic production of O2 by zooxanthellae and the rate of light calcification, 3) at month 3, there was a decrease in both light and dark calcification rates, the appearance of the first oxidative damage in the zooxanthellae, the disruption of symbiosis, 4) and finally the death of corals at month 6.
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- 2008
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28. Catalase characterization and implication in bleaching of a symbiotic sea anemone.
- Author
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Merle PL, Sabourault C, Richier S, Allemand D, and Furla P
- Subjects
- Amino Acid Sequence, Animals, Catalase genetics, Ectoderm enzymology, Electrophoresis, Polyacrylamide Gel, Endoderm enzymology, Humans, Hydrogen-Ion Concentration, Immunoblotting, Isoenzymes metabolism, Molecular Sequence Data, Sequence Homology, Amino Acid, Spectrophotometry, Temperature, Catalase metabolism, Eukaryota physiology, Sea Anemones enzymology, Sea Anemones microbiology, Symbiosis physiology
- Abstract
Symbiotic cnidarians are marine invertebrates harboring photosynthesizing microalgae (named zooxanthellae), which produce great amounts of oxygen and free radicals upon illumination. Studying antioxidative balance is then crucial to understanding how symbiotic cnidarians cope with ROS production. In particular, it is suspected that oxidative stress triggers cnidarian bleaching, i.e., the expulsion of zooxanthellae from the animal host, responsible for symbiotic cnidarian mass mortality worldwide. This study therefore investigates catalase antioxidant enzymes and their role in bleaching of the temperate symbiotic sea anemone Anemonia viridis. Using specific separation of animal tissues (ectoderm and endoderm) from the symbionts (zooxanthellae), spectrophotometric assays and native PAGE revealed both tissue-specific and activity pattern distribution of two catalase electrophoretypes, E1 and E2. E1, expressed in all three tissues, presents high sensitivity to the catalase inhibitor aminotriazole (ATZ) and elevated temperatures. The ectodermal E1 form is responsible for 67% of total catalase activity. The E2 form, expressed only within zooxanthellae and their host endodermal cells, displays low sensitivity to ATZ and relative thermostability. We further cloned an ectodermal catalase, which shares 68% identity with mammalian monofunctional catalases. Last, 6 days of exposure of whole sea anemones to ATZ (0.5 mM) led to effective catalase inhibition and initiated symbiont expulsion. This demonstrates the crucial role of this enzyme in cnidarian bleaching, a phenomenon responsible for worldwide climate-change-induced mass mortalities, with catastrophic consequences for marine biodiversity.
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- 2007
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29. Oxidative stress and apoptotic events during thermal stress in the symbiotic sea anemone, Anemonia viridis.
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Richier S, Sabourault C, Courtiade J, Zucchini N, Allemand D, and Furla P
- Subjects
- Amino Acid Sequence, Anemone enzymology, Anemone parasitology, Animals, Base Sequence, Caspases genetics, Caspases metabolism, DNA, Complementary, Hot Temperature, In Vitro Techniques, Molecular Sequence Data, Phylogeny, Reverse Transcriptase Polymerase Chain Reaction, Seawater parasitology, Sequence Alignment, Anemone physiology, Apoptosis, Dinoflagellida physiology, Oxidative Stress, Symbiosis
- Abstract
Symbiosis between cnidarian and photosynthetic protists is widely distributed over temperate and tropical seas. These symbioses can periodically breakdown, a phenomenon known as cnidarian bleaching. This event can be irreversible for some associations subjected to acute and/or prolonged environmental disturbances, and leads to the death of the animal host. During bleaching, oxidative stress has been described previously as acting at molecular level and apoptosis is suggested to be one of the mechanisms involved. We focused our study on the role of apoptosis in bleaching via oxidative stress in the association between the sea anemone Anemonia viridis and the dinoflagellates Symbiodinium species. Characterization of caspase-like enzymes were conducted at the biochemical and molecular level to confirm the presence of a caspase-dependent apoptotic phenomenon in the cnidarian host. We provide evidence of oxidative stress followed by induction of caspase-like activity in animal host cells after an elevated temperature stress, suggesting the concomitant action of these components in bleaching.
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- 2006
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30. The Symbiotic Anthozoan: A Physiological Chimera between Alga and Animal.
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Furla P, Allemand D, Shick JM, Ferrier-Pagès C, Richier S, Plantivaux A, Merle PL, and Tambutté S
- Abstract
The symbiotic life style involves mutual ecological, physiological, structural, and molecular adaptations between the partners. In the symbiotic association between anthozoans and photosynthetic dinoflagellates (Symbiodinium spp., also called zooxanthellae), the presence of the endosymbiont in the animal cells has constrained the host in several ways. It adopts behaviors that optimize photosynthesis of the zooxanthellae. The animal partner has had to evolve the ability to absorb and concentrate dissolved inorganic carbon from seawater in order to supply the symbiont's photosynthesis. Exposing itself to sunlight to illuminate its symbionts sufficiently also subjects the host to damaging solar ultraviolet radiation. Protection against this is provided by biochemical sunscreens, including mycosporine-like amino acids, themselves produced by the symbiont and translocated to the host. Moreover, to protect itself against oxygen produced during algal photosynthesis, the cnidarian host has developed certain antioxidant defenses that are unique among animals. Finally, living in nutrient-poor waters, the animal partner has developed several mechanisms for nitrogen assimilation and conservation such as the ability to absorb inorganic nitrogen, highly unusual for a metazoan. These facts suggest a parallel evolution of symbiotic cnidarians and plants, in which the animal host has adopted characteristics usually associated with phototrophic organisms.
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- 2005
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31. Symbiosis-induced adaptation to oxidative stress.
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Richier S, Furla P, Plantivaux A, Merle PL, and Allemand D
- Subjects
- Animals, Chlorophyll metabolism, Enzyme-Linked Immunosorbent Assay, Mediterranean Sea, Oxygen metabolism, Proteins metabolism, Superoxide Dismutase metabolism, Thiobarbiturates metabolism, Adaptation, Physiological, Dinoflagellida, Oxidative Stress physiology, Sea Anemones physiology, Symbiosis
- Abstract
Cnidarians in symbiosis with photosynthetic protists must withstand daily hyperoxic/anoxic transitions within their host cells. Comparative studies between symbiotic (Anemonia viridis) and non-symbiotic (Actinia schmidti) sea anemones show striking differences in their response to oxidative stress. First, the basal expression of SOD is very different. Symbiotic animal cells have a higher isoform diversity (number and classes) and a higher activity than the non-symbiotic cells. Second, the symbiotic animal cells of A. viridis also maintain unaltered basal values for cellular damage when exposed to experimental hyperoxia (100% O(2)) or to experimental thermal stress (elevated temperature +7 degrees C above ambient). Under such conditions, A. schmidti modifies its SOD activity significantly. Electrophoretic patterns diversify, global activities diminish and cell damage biomarkers increase. These data suggest symbiotic cells adapt to stress while non-symbiotic cells remain acutely sensitive. In addition to being toxic, high O(2) partial pressure (P(O(2))) may also constitute a preconditioning step for symbiotic animal cells, leading to an adaptation to the hyperoxic condition and, thus, to oxidative stress. Furthermore, in aposymbiotic animal cells of A. viridis, repression of some animal SOD isoforms is observed. Meanwhile, in cultured symbionts, new activity bands are induced, suggesting that the host might protect its zooxanthellae in hospite. Similar results have been observed in other symbiotic organisms, such as the sea anemone Aiptasia pulchella and the scleractinian coral Stylophora pistillata. Molecular or physical interactions between the two symbiotic partners may explain such variations in SOD activity and might confer oxidative stress tolerance to the animal host.
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- 2005
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32. Molecular characterization of two CuZn-superoxide dismutases in a sea anemone.
- Author
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Plantivaux A, Furla P, Zoccola D, Garello G, Forcioli D, Richier S, Merle PL, Tambutté E, Tambutté S, and Allemand D
- Subjects
- Amino Acid Sequence, Animals, Base Sequence, Cloning, Molecular, Gene Expression Regulation, Genes, In Situ Hybridization, Molecular Sequence Data, Open Reading Frames, Oxidation-Reduction, Oxidative Stress, Oxygen metabolism, Photosynthesis, Phylogeny, Reverse Transcriptase Polymerase Chain Reaction, Sea Anemones cytology, Sea Anemones genetics, Sequence Alignment, Sequence Homology, Amino Acid, Superoxide Dismutase genetics, Superoxide Dismutase metabolism, Symbiosis, Zooplankton physiology, Sea Anemones enzymology, Superoxide Dismutase isolation & purification
- Abstract
Cnidarians living in symbiosis with photosynthetic cells--called zooxanthellae--are submitted to high oxygen levels generated by photosynthesis. To cope with this hyperoxic state, symbiotic cnidarians present a high diversity of superoxide dismutases (SOD) isoforms. To understand better the mechanism of resistance of cnidarian hosts to hyperoxia, we studied copper- and zinc-containing SOD (CuZnSOD) from Anemonia viridis, a temperate symbiotic sea anemone. We cloned two CuZnSOD genes that we call AvCuZnSODa and AvCuZnSODb. Their molecular analysis suggests that the AvCuZnSODa transcript encodes an extracellular form of CuZnSOD, whereas the AvCuZnSODb transcript encodes an intracellular form. Using in situ hybridization, we showed that both AvCuZnSODa and AvCuZnSODb transcripts are expressed in the endodermal and ectodermal cells of the sea anemone, but not in the zooxanthellae. The genomic flanking sequences of AvCuZnSODa and AvCuZnSODb revealed different putative binding sites for transcription factors, suggesting different modes of regulation for the two genes. This study represents a first step in the understanding of the molecular mechanisms of host animal resistance to permanent hyperoxia status resulting from the photosynthetic symbiosis. Moreover, AvCuZnSODa and AvCuZnSODb are the first SODs cloned from a diploblastic animal, contributing to the evolutionary understanding of SODs.
- Published
- 2004
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33. Characterization of superoxide dismutases in anoxia- and hyperoxia-tolerant symbiotic cnidarians.
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Richier S, Merle PL, Furla P, Pigozzi D, Sola F, and Allemand D
- Subjects
- Animals, Isoenzymes metabolism, Light, Oxygen analysis, Sea Anemones metabolism, Seawater analysis, Symbiosis, Time Factors, Cnidaria metabolism, Oxygen metabolism, Superoxide Dismutase metabolism
- Abstract
Many cnidarians, such as sea anemones, contain photosynthetic symbiotic dinoflagellates called zooxanthellae. During a light/dark cycle, the intratentacular O(2) state changes in minutes from hypoxia to hyperoxia (3-fold normoxia). To understand the origin of the high tolerance to these unusual oxic conditions, we have characterized superoxide dismutases (SODs) from the three cellular compartments (ectoderm, endoderm and zooxanthellae) of the Mediterranean sea anemone Anemonia viridis. The lowest SOD activity was found in ectodermal cells while endodermal cells and zooxanthellae showed a higher SOD activity. Two, seven and six SOD activity bands were identified on native PAGE in ectoderm, endoderm and zooxanthellae, respectively. A CuZnSOD was identified in both ectodermal and endodermal tissues. MnSODs were detected in all compartments with two different subcellular localizations. One band displays a classical mitochondrial localization, the three others being extramitochondrial. FeSODs present in zooxanthellae also appeared in endodermal host tissue. The isoelectric points of all SODs were distributed between 4 and 5. For comparative study, a similar analysis was performed on the whole homogenate of a scleractinian coral Stylophora pistillata. These results are discussed in the context of tolerance to hyperoxia and to the transition from anoxia to hyperoxia.
- Published
- 2003
- Full Text
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