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1. Geochemistry of an endorheic thalassohaline ecosystem: the Dziani Dzaha crater lake (Mayotte Archipelago, Indian Ocean)

Author

Sarazin, Gérard, Jézéquel, Didier, Leboulanger, Christophe, Fouilland, Eric, Le Floc’h, Emilie, Bouvy, Marc, Gérard, Emmanuelle, Agogué, Hélène, Bernard, Cécile, Hugoni, Mylène, Grossi, Vincent, Troussellier, Marc, and Ader, Magali

Subjects
Thalassohaline lake, Endorheic ecosystem, Cyanobacteria, Methane emission, Biogeochemistry, Mayotte, Geophysics. Cosmic physics, QC801-809, Chemistry, QD1-999, Geology, QE1-996.5
Abstract

Dziani Dzaha is a maar the age of which is close to 4000 years. While its water is thought to have originated from seawater it is now considered as an extreme environment due to its hypersaline and alkaline characteristics. Those extreme features have led to the simplification of the trophic network. Cyanobacteria account for up to 95% of the photosynthetic biomass. The main biogeochemical processes, i.e. photosynthesis, bacterial sulfate reduction and methanogenesis could explain the current water composition. As far as we know, this ecosystem could be unique on Earth, extending the nature and chemical limits of aquatic inland ecosystems.

Published
2020
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5. Molecular Phylogeny, Morphology, Growth and Toxicity of Three Benthic Dinoflagellates Ostreopsis sp. 9, Prorocentrum lima and Coolia monotis Developing in Strait of Gibraltar, Southwestern Mediterranean

Author

Ibghi, Mustapha, Rijal Leblad, Benlahcen, L’bachir El Kbiach, Mohammed, Aboualaalaa, Hicham, Daoudi, Mouna, Masseret, Estelle, Le Floc'H, Emilie, Hervé, Fabienne, Bilien, Gwenael, Chomerat, Nicolas, Amzil, Zouher, Laabir, Mohamed, Ibghi, Mustapha, Rijal Leblad, Benlahcen, L’bachir El Kbiach, Mohammed, Aboualaalaa, Hicham, Daoudi, Mouna, Masseret, Estelle, Le Floc'H, Emilie, Hervé, Fabienne, Bilien, Gwenael, Chomerat, Nicolas, Amzil, Zouher, and Laabir, Mohamed

Abstract

Few works have been carried out on benthic harmful algal blooms (BHAB) species in the southern Mediterranean and no data are available for the highly dynamic Strait of Gibraltar (western Mediterranean waters). For the first time, Ostreopsis sp. 9, Prorocentrum lima and Coolia monotis were isolated in this key region in terms of exchanges between the Atlantic Ocean and the Mediterranean and subject to intense maritime traffic. Ribotyping confirmed the morphological identification of these three dinoflagellates species. Monoclonal cultures were established and the maximum growth rate and cell yield were measured at a temperature of 24 °C and an irradiance of 90 µmol photons m−2 s−1, for each species: 0.26 ± 0.02 d−1 (8.75 × 103 cell mL−1 after 28 days) for Ostreopsis sp. 9, 0.21 ± 0.01 d−1 (49 × 103 cell mL−1 after 145 days) for P. lima and 0.21 ± 0.01 d−1 (10.02 × 103 cell mL−1 after 28 days) for C. monotis. Only P. lima was toxic with concentrations of okadaic acid and dinophysistoxin-1 measured in optimal growth conditions ranging from 6.4 pg cell−1 to 26.97 pg cell−1 and from 5.19 to 25.27 pg cell−1, respectively. The toxin content of this species varied in function of the growth phase. Temperature influenced the growth and toxin content of P. lima. Results suggest that future warming of Mediterranean coastal waters may lead to higher growth rates and to increases in cellular toxin levels in P. lima. Nitrate and ammonia affected the toxin content of P. lima but no clear trend was noted. In further studies, we have to isolate other BHAB species and strains from Strait of Gibraltar waters to obtain more insight into their diversity and toxicity.

Published
2024
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6. Comparison of methods for DMSP measurements in dinoflagellate cultures

Author

Caruana, Amandine, Bucciarelli, Eva, Deleporte, Céline, Le Floc'H, Emilie, Hervé, Fabienne, Le Goff, Manon, Caruana, Amandine, Bucciarelli, Eva, Deleporte, Céline, Le Floc'H, Emilie, Hervé, Fabienne, and Le Goff, Manon

Abstract

A comparison of three analytical methods (the indirect GC‐FPD and MIMS, and direct LC‐MS/MS) for dimethylsulfoniopropionate (DMSP) measurements was conducted to assess their accuracy and reliability. The three methods showed a linear response but are distinguished by their linearity range, the largest being for MIMS. All three methods showed good precision on Alexandrium minutum samples (2–12%). The variability between the three methods when comparing analyses of A. minutum replicates was 11%, with the DMSP measurements by LC‐MS/MS being the highest. This result also confirms that indirect DMSP measurement after hydrolysis for GC or MIMS methods does not lead to an overestimation of DMSP values in A. minutum. A special focus was made on the more recent LC‐MS/MS method including further assays in sample preparation and storage from cultures of the dinoflagellate A. minutum. Dinoflagellate cells should be harvested by gentle filtration (< 5 cm Hg) or slow centrifugation (500 × g) to retrieve the largest DMSP pool. For the LC‐MS/MS method, MeOH used for cell extraction should be added prior to freezing (to prevent DMSP degradation). Samples will then be stable in frozen storage for at least 2 months. Finally, direct and indirect methods are complementary for identifying the exact DMSP fraction among dimethylsulfide‐producing compounds that compose total and particulate DMSP pools issued from newly screened organisms or environmental samples.

Published
2024
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8. Molecular Phylogeny, Morphology, Growth and Toxicity of Three Benthic Dinoflagellates Ostreopsis sp. 9, Prorocentrum lima and Coolia monotis Developing in Strait of Gibraltar, Southwestern Mediterranean

Author

Ibghi, Mustapha, primary, Rijal Leblad, Benlahcen, additional, L’Bachir El Kbiach, Mohammed, additional, Aboualaalaa, Hicham, additional, Daoudi, Mouna, additional, Masseret, Estelle, additional, Le Floc’h, Emilie, additional, Hervé, Fabienne, additional, Bilien, Gwenael, additional, Chomerat, Nicolas, additional, Amzil, Zouher, additional, and Laabir, Mohamed, additional

Published
2024
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15. Marine ecological aquaculture: a successful Mediterranean integrated multi-trophic aquaculture case study of a fish, oyster and algae assemblage

Author

Roque D'Orbcastel, Emmanuelle, Lutier, Mathieu, Le Floc'H, Emilie, Ruelle, Francois, Triplet, Sebastien, Le Gall, Patrik, Hubert, Clarisse, Fortune, Martine, Laugier, Thierry, Geoffroy, Thibault, Crottier, Anaïs, Gobet, Angélique, Fouilland, Eric, Roque D'Orbcastel, Emmanuelle, Lutier, Mathieu, Le Floc'H, Emilie, Ruelle, Francois, Triplet, Sebastien, Le Gall, Patrik, Hubert, Clarisse, Fortune, Martine, Laugier, Thierry, Geoffroy, Thibault, Crottier, Anaïs, Gobet, Angélique, and Fouilland, Eric

Abstract

Inspired by agroecology, ecological aquaculture proposes an alternative model that uses ecology as a paradigm to develop innovative, more eco-friendly aquaculture with environmental, economic and social benefits. Integrated multi-trophic aquaculture (IMTA) is one application of this principle. Inspired by the natural trophic chain, it associates primary producers with primary or secondary consumers, providing a new source of biomass without requiring supplementary feed by recycling inorganic and organic wastes. Of these systems, land-based IMTA demonstrate several advantages, especially easier control of nutrient flows, contaminants and/or predators. This study focused on a land-based marine IMTA, combining a recirculating aquaculture system for fish consecutively with a natural marine polyculture of microalgae and oyster cultivation. The objective was to assess the ability of the microalgal polyculture both to bioremediate fish nutrients and to sustain oyster growth. For the first time in a Mediterranean climate, we confirmed the feasibility of developing a microalgae community of interest for oysters maintained by fish effluent. Despite strong variability in microalgae production, this IMTA system resulted in significant oyster growth over the experimental period of 1 month, with growth results of the same order of magnitude as natural juvenile growth. In the conditions tested, this IMTA with reduced human intervention allowed a gain in recoverable biomass of 3.7 g of oyster produced per killogramme of fish feed distributed. By transforming waste into additional biomass, IMTA offer a more promising, ecological avenue for aquaculture, based on a circular economy, which may in turn increase the social acceptability of fish farming.

Published
2022
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18. Marine ecological aquaculture: a successful Mediterranean integrated multi-trophic aquaculture case study of a fish, oyster and algae assemblage.

Author

D'Orbcastel, Emmanuelle Roque, Lutier, Mathieu, Le Floc'h, Emilie, Ruelle, François, Triplet, Sébastien, Le Gall, Patrik, Hubert, Clarisse, Fortune, Martine, Laugier, Thierry, Geoffroy, Thibault, Crottier, Anaïs, Gobet, Angélique, and Fouilland, Eric

Subjects
MARICULTURE, ORGANIC waste recycling, AQUACULTURE, FISH farming, OYSTERS, DUNALIELLA, HOUGH transforms, FEEDING tubes
Abstract

Inspired by agroecology, ecological aquaculture proposes an alternative model that uses ecology as a paradigm to develop innovative, more eco-friendly aquaculture with environmental, economic and social benefits. Integrated multi-trophic aquaculture (IMTA) is one application of this principle. Inspired by the natural trophic chain, it associates primary producers with primary or secondary consumers, providing a new source of biomass without requiring supplementary feed by recycling inorganic and organic wastes. Of these systems, land-based IMTA demonstrate several advantages, especially easier control of nutrient flows, contaminants and/or predators. This study focused on a land-based marine IMTA, combining a recirculating aquaculture system for fish consecutively with a natural marine polyculture of microalgae and oyster cultivation. The objective was to assess the ability of the microalgal polyculture both to bioremediate fish nutrients and to sustain oyster growth. For the first time in a Mediterranean climate, we confirmed the feasibility of developing a microalgae community of interest for oysters maintained by fish effluent. Despite strong variability in microalgae production, this IMTA system resulted in significant oyster growth over the experimental period of 1 month, with growth results of the same order of magnitude as natural juvenile growth. In the conditions tested, this IMTA with reduced human intervention allowed a gain in recoverable biomass of 3.7 g of oyster produced per killogramme of fish feed distributed. By transforming waste into additional biomass, IMTA offer a more promising, ecological avenue for aquaculture, based on a circular economy, which may in turn increase the social acceptability of fish farming. [ABSTRACT FROM AUTHOR]

Published
2022
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20. Geochemistry of an endorheic thalassohaline ecosystem: the Dziani Dzaha crater lake (Mayotte Archipelago, Indian Ocean)

Author

Sarazin, Gérard, primary, Jézéquel, Didier, additional, Leboulanger, Christophe, additional, Fouilland, Eric, additional, Le Floc’h, Emilie, additional, Bouvy, Marc, additional, Gérard, Emmanuelle, additional, Agogué, Hélène, additional, Bernard, Cécile, additional, Hugoni, Mylène, additional, Grossi, Vincent, additional, Troussellier, Marc, additional, and Ader, Magali, additional

Published
2021
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22. Demonstration of facilitation between microalgae to face ammonia toxicity

Author

Krichen, Emna, Rapaport, Alain, Le Floc'h, Emilie, Fouilland, Eric, Mathématiques, Informatique et STatistique pour l'Environnement et l'Agronomie (MISTEA), Institut National de la Recherche Agronomique (INRA)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)-Institut National de la Recherche Agronomique (INRA), Fouilland, Eric, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), and Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD)

Subjects
[SDE.BE] Environmental Sciences/Biodiversity and Ecology, [SDE.IE]Environmental Sciences/Environmental Engineering, fungi, [SDE.IE] Environmental Sciences/Environmental Engineering, [SDV.EE.IEO] Life Sciences [q-bio]/Ecology, environment/Symbiosis, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, [SDV.EE.IEO]Life Sciences [q-bio]/Ecology, environment/Symbiosis
Abstract

Positive interactions such as facilitation play an important role during the biological colonization and species succession in harsh or changing environments. However, the direct evidence of such ecological interaction in microbial communities remains rare. Using common freshwater microalgae isolated from a High Rate Algal Pond (HRAP) treating wastewaters, we investigated with both experimental and modelling approaches the direct facilitation between two algal strains during the colonization phase. Our results demonstrate that the first colonization by microalgae under a severe chemical condition arose from the rapid growth of pioneer species such as Chlorella sorokiniana, which facilitated the subsequent colonization of low growth specialists such as Scenedesmus pectinatus. The pioneer species rapidly depleted the total available ammonia nitrogen favouring the specialist species initially inhibited by free ammonia toxicity. This latter species ultimately dominated the algal community in accordance with the competitive exclusion under low nutrient conditions. We show that microbial successions are not only regulated by climatic conditions but also by interactions between species based on the ability to indirectly modify their growth conditions. Furthermore, the theoretical study of algal resilience and succession times as proxies of the facilitation efficiency showed that control of algal production processes might be possible by modifying the initial populations' densities.

Published
2019

23. Demonstration of facilitation between microalgae to face ammonia toxicity in a High Rate Algal Pond

Author

Krichen, Emna, Rapaport, Alain, Fouilland, Eric, Le Floc'h, Emilie, Mathématiques, Informatique et STatistique pour l'Environnement et l'Agronomie (MISTEA), Institut National de la Recherche Agronomique (INRA)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), and Universidad de Valladolid (Valladolid). Valladolid, ESP.

Subjects
[SDV.BV]Life Sciences [q-bio]/Vegetal Biology, [INFO.INFO-MO]Computer Science [cs]/Modeling and Simulation
Abstract

Wastewater treatment using extensive microalgae cultivation in High Rate Algal Ponds (HRAPs) has gained increasing interest for bioremediation and potential biomass valorization. The presence of growth inhibitors in such systems may damage the algae culture and thus influence the stability and economic viability, which are of crucial importance during the wastewater treatment process. Several studies highlighted the importance of biotic factors, particularly microalgal diversity, in maintaining stable biomass productivity in HRAPs (Cho et al. 2017, Gales et al. 2019). However, in most studies, the successional trends of microalgal species growing in HRAPs have been interpreted as responses to predation and/or seasonal factors, while much fewer studies have discussed the role of positive interactions. In this study, we validate using both experimental and modeling grounds on single strains the hypothesis of positive interaction between the common freshwater microalgal species (Chlorella sp. and Scenedesmus sp.) isolated from HRAP under external stress (free ammonia (NH3) toxicity) during the colonization phase of HRAP.

Published
2019

24. Facilitation écologique entre deux espèces de microalgues Chlorella sorokiniana & Scenedesmus acutus

Author

Krichen, Emna, Le Floc'H, Emilie, Rapaport, Alain, Fouilland, Eric, Mathématiques, Informatique et STatistique pour l'Environnement et l'Agronomie (MISTEA), Institut National de la Recherche Agronomique (INRA)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), and ProdInra, Migration

Subjects
[SDV.BV]Life Sciences [q-bio]/Vegetal Biology, [SDV.BV] Life Sciences [q-bio]/Vegetal Biology, [INFO.INFO-MO] Computer Science [cs]/Modeling and Simulation, [INFO.INFO-BI]Computer Science [cs]/Bioinformatics [q-bio.QM], [INFO.INFO-MO]Computer Science [cs]/Modeling and Simulation, [INFO.INFO-BI] Computer Science [cs]/Bioinformatics [q-bio.QM]
Abstract

National audience; Une facilitation écologique entre deux espèces de microalgues Chlorella sorokiniana et Scenedesmus acutus, classiquement observées dans les eaux fortement anthropisées, riches en ammonium (NH4+), est démontrée. En effet, des expérimentations en laboratoire ont montré que la croissance de Scenedesmus acutus est inhibée pour les très fortes valeurs d'ammonium (NH4+), à cause de la toxicité en ammoniaque (NH3), ce qui n'est pas le cas pour Chlorella sorokiniana. Cette dernière espèce possède toutefois une affinité pour le (NH4+), plus faible que Scenedesmus acutus. Une modélisation mathématique a été réalisée à partir de ces résultats expérimentaux et a permis de démontrer la succession écologique de ces espèces lorsqu'elles sont présentes ensemble. Ainsi lors d'apports très riches en NH4+, la croissance rapide de C. sorokiniana colonise en premier le milieu, réduisant la teneur en NH4+ (et donc en NH3 permettant à S. acutus de croître (facilitation) et même de gagner la compétition pour ce nutriment.

Published
2018

25. Role of microalgae in a landbased multi-trophic aquaculture system: bioremediation, production, biochemical composition

Author

Roque d’Orbcastel, Emmanuelle, Lutier, M., Le Floc'h, Emilie, Nahon, Sarah, Triplet, Sébastien, Geoffroy, Thibault, Callier, Myriam D., Fouilland, Eric, MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Nutrition, Métabolisme, Aquaculture (NuMéA), Institut National de la Recherche Agronomique (INRA)-Université de Pau et des Pays de l'Adour (UPPA), LSEA, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), and European Aquaculture Society (EAS).

Subjects
Animal biology, huître, composition biochimique, aquaculture, microalgae, [SDV.BA]Life Sciences [q-bio]/Animal biology, Biologie animale, système aquacole, phytoremediation, dicentrarchus labrax, bioremédiation
Abstract

Résumé; Role of microalgae in a landbased multi-trophic aquaculture system: bioremediation, production, biochemical composition. World Aquaculture 2018

Published
2018

26. Assessment of bacterial dependence on marine primary production along a northern latitudinal gradient

Author

Fouilland, Eric, Le Floc'H, Emilie, Brennan, Debra, Bell, Elanor M., Lordsmith, Sian L., Mcneill, Sharon, Mitchell, Elaine, Brand, Tim D., Garcia-martin, E. Elena, Leakey, Raymond J. G., Fouilland, Eric, Le Floc'H, Emilie, Brennan, Debra, Bell, Elanor M., Lordsmith, Sian L., Mcneill, Sharon, Mitchell, Elaine, Brand, Tim D., Garcia-martin, E. Elena, and Leakey, Raymond J. G.

Abstract

Recent observations in polar marine waters have shown that a large fraction of primary production may be lost to respiration by planktonic bacteria due to very low bacterial growth efficiencies in cold waters. Here we report that sea temperature may be a key factor influencing the interaction between bacteria and primary production in North Atlantic and Arctic waters, suggesting that low primary production rates could not sustain bacterial carbon demand in the coldest Arctic waters. The use of freshly produced phytoplankton exudate by bacteria in early- and mid-summer was assessed, together with the bacterial uptake of dissolved inorganic nitrogen (DIN = nitrate and ammonium), in surface waters along a latitudinal gradient from the North Sea to the Arctic sea ice. Bacterial production was independent of the low primary production measured in the coldest waters. Under these conditions, heterotrophic bacteria can consume a large fraction of DIN and N-rich organic matter, making them strong contributors to N fluxes in these waters.

Published
2018
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27. Microbial Diversity and Cyanobacterial Production in Dziani Dzaha Crater Lake, a Unique Tropical Thalassohaline Environment

Author

Leboulanger, Christophe, Agogué, Hélène, Bernard, Cécile, Bouvy, Marc, Carré, Claire, Cellamare, Maria, Duval, Charlotte, Fouilland, Eric, Got, Patrice, Intertaglia, Laurent, Lavergne, Céline, Le Floc'h, Emilie, Roques, Cécile, Sarazin, Gérard, MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), LIttoral ENvironnement et Sociétés - UMR 7266 (LIENSs), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), Molécules de Communication et Adaptation des Micro-Organismes (MCAM), Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS), Observatoire océanologique de Banyuls (OOB), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), LIttoral ENvironnement et Sociétés (LIENSs), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Muséum national d'Histoire naturelle (MNHN)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), LIttoral ENvironnement et Sociétés - UMRi 7266 (LIENSs), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD), Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut National de la Santé et de la Recherche Médicale (INSERM), and Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
Chlorophyll, [SDV]Life Sciences [q-bio], lcsh:Medicine, Marine and Aquatic Sciences, Biochemistry, Comoros, RNA, Ribosomal, 16S, Cluster Analysis, Biomass, Photosynthesis, lcsh:Science, Islands, Principal Component Analysis, Geography, Ecology, Temperature, Biodiversity, Hydrogen-Ion Concentration, Plants, Plankton, Nucleic acids, Chemistry, Ribosomal RNA, Physical Sciences, [SDE]Environmental Sciences, Water Microbiology, Research Article, Freshwater Environments, Chemical Elements, Cell biology, Cellular structures and organelles, Ecological Metrics, Algae, Nitrogen, Biomass (Ecology), Cyanobacteria, Surface Water, Sea Water, Animals, Non-coding RNA, Models, Statistical, Bacteria, Chlorophyll A, lcsh:R, Ecology and Environmental Sciences, Organisms, Aquatic Environments, Biology and Life Sciences, Bodies of Water, Invertebrates, Carbon, Oxygen, Lakes, Phytoplankton, Earth Sciences, RNA, lcsh:Q, Hydrology, Ribosomes
Abstract

International audience; This study describes, for the first time, the water chemistry and microbial diversity in Dziani Dzaha, a tropical crater lake located on Mayotte Island (Comoros archipelago, Western Indian Ocean). The lake water had a high level of dissolved matter and high alkalinity (10.6–14.5 g L-1 eq. CO32-, i.e. 160–220 mM compare to around 2–2.5 in seawater), with salinity up to 52 psu, 1.5 higher than seawater. Hierarchical clustering discriminated Dziani Dzaha water from other alkaline, saline lakes, highlighting its thalassohaline nature. The phytoplankton biomass was very high, with a total chlorophyll a concentration of 524 to 875 μg chl a L-1 depending on the survey, homogeneously distributed from surface to bottom (4 m). Throughout the whole water column the photosynthetic biomass was dominated (>97% of total biovolume) by the filamentous cyanobacteria Arthrospira sp. with a straight morphotype. In situ daily photosynthetic oxygen production ranged from 17.3 to 22.2 g O2 m-2 d-1, consistent with experimental production / irradiance measurements and modeling. Heterotrophic bacterioplankton was extremely abundant, with cell densities up to 1.5 108 cells mL-1 in the whole water column. Isolation and culture of 59 Eubacteria strains revealed the prevalence of alkaliphilic and halophilic organisms together with taxa unknown to date, based on 16S rRNA gene analysis. A single cloning-sequencing approach using archaeal 16S rDNA gene primers unveiled the presence of diverse extremophilic Euryarchaeota. The water chemistry of Dziani Dzaha Lake supports the hypothesis that it was derived from seawater and strongly modified by geological conditions and microbial activities that increased the alkalinity. Dziani Dzaha has a unique consortium of cyanobacteria, phytoplankton, heterotrophic Eubacteria and Archaea, with very few unicellular protozoa, that will deserve further deep analysis to unravel its uncommon diversity. A single taxon, belonging to the genus Arthrospira, was found responsible for almost all photosynthetic primary production.

Published
2017
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28. Significance of plankton community structure and nutrient availability for the control of dinoflagellate blooms by parasites: a modeling approach

Author

Alves-de-souza, Catharina, Pecqueur, David, Le Floc'H, Emilie, Mas, Sebastien, Roques, Cecile, Mostajir, Behzad, Vidussi, Franscesca, Velo-suarez, Lourdes, Sourisseau, Marc, Fouilland, Eric, Guillou, Laure, Universidade Federal do Rio de Janeiro (UFRJ), MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Observatoire de REcherche Méditerranéen de l'Environnement (OSU OREME), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Montpellier 2 - Sciences et Techniques (UM2), Département Dyneco Pelagos, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Diversité et Interactions au sein du Plancton Océanique (DIPO), Adaptation et diversité en milieu marin (ADMM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Station biologique de Roscoff [Roscoff] (SBR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Station biologique de Roscoff [Roscoff] (SBR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Laboratoire d'Ecologie Pélagique (PELAGOS), Dynamiques des Écosystèmes Côtiers (DYNECO), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Adaptation et diversité en milieu marin (AD2M), Station biologique de Roscoff [Roscoff] (SBR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Station biologique de Roscoff [Roscoff] (SBR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD), Université de Montpellier (UM)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut national des sciences de l'Univers (INSU - CNRS), Unité Dyneco, Laboratoire Pelagos, and Dynamiques de l'Environnement Côtier (DYNECO)

Subjects
fungi, lcsh:R, lcsh:Medicine, Numerical Analysis, Computer-Assisted, Eutrophication, Plankton, Models, Biological, Food, parasitic diseases, Dinoflagellida, Animals, Computer Simulation, Parasites, lcsh:Q, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, lcsh:Science, Research Article
Abstract

International audience; Dinoflagellate blooms are frequently observed under temporary eutrophication of coastal waters after heavy rains. Growth of these opportunistic microalgae is believed to be promoted by sudden input of nutrients and the absence or inefficiency of their natural enemies, such as grazers and parasites. Here, numerical simulations indicate that increasing nutrient availability not only promotes the formation of dinoflagellate blooms but can also stimulate their control by protozoan parasites. Moreover, high abundance of phytoplankton other than dinoflagellate hosts might have a significant dilution effect on the control of dinoflagellate blooms by parasites, either by resource competition with dinoflagellates (thus limiting the number of hosts available for infection) or by affecting numerical-functional responses of grazers that consume free-living parasite stages. These outcomes indicate that although both dinoflagellates and their protozoan parasites are directly affected by nutrient availability , the efficacy of the parasitic control of dinoflagellate blooms under temporary eutrophication depends strongly on the structure of the plankton community as a whole.

Published
2015
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29. Control of the pH for marine microalgae polycultures: A key point for CO2fixation improvement in intensive cultures

Author

Galès, Amandine, Triplet, Sébastien, Geoffroy, Thibault, Roques, Cécile, Carré, Claire, Le Floc’h, Emilie, Lanfranchi, Mélissa, Simier, Monique, Roque d’Orbcastel, Emmanuelle, Przybyla, Cyrille, and Fouilland, Eric

Abstract

•The highest conversion of CO2into carbon biomass was reached at pH 7.•The theoretical maximal biological conversion of CO2was estimated to be ca.60 %.•Lower and higher pH favoured respectively the amoebae and copepod development.•pH can be a tool for favouring one microalgal species among a natural assemblage.

Published
2020
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31. Impacts des aléas climatiques en élevages bovin et ovin allaitants et demande de couverture assurantielle

Author

Mosnier, Claire, Fourdin, Simon, Moreau, Jean-Christophe, Boutry, Anaïs, Le Floc'h, Emilie, Devun, Jean, and Lherm, Michel

Subjects
ovin allaitant, risque climatique, élevage bovin, sensibilité aux aléas, adaptation, assurance, alea climatique, prairie, élevage bovin allaitant, Milieux et Changements globaux, élevage ovin, agriculture
Abstract

Améliorer les capacités d’adaptation des élevages aux aléas climatiques et développer des outils d’assurance couvrant la production des prairies contre ces risques constituent un enjeu majeur dans une perspective de transition du régime public des calamités agricoles vers les assurances privées. S’appuyant sur l’analyse d’un large panel de données d’exploitations « allaitantes » sur la période 2000-2009, cette étude a pour premier objectif de quantifier la sensibilité des résultats économiques des exploitations aux aléas climatiques et d’identifier les leviers techniques mobilisés par les producteurs pour leur faire face. À partir d’enquêtes réalisées dans différentes régions, son second objectif est de mieux cerner les visions que les éleveurs ont des aléas climatiques, leurs façons de gérer ce risque ainsi que leurs motivations à souscrire une assurance « prairie ».

Published
2014

33. Pelagic population dynamics of Aureliasp. in French Mediterranean lagoons

Author

Marques, Raquel, Albouy-Boyer, Severine, Delpy, Floriane, Carre, Claire, Le Floc'h, Emilie, Roques, Cecile, Molinero, Juan Carlos, Bonnet, Delphine, Marques, Raquel, Albouy-Boyer, Severine, Delpy, Floriane, Carre, Claire, Le Floc'h, Emilie, Roques, Cecile, Molinero, Juan Carlos, and Bonnet, Delphine

Abstract

The pelagic dynamics of the cosmopolitan scyphozoan Aurelia sp. was investigated in three French Mediterranean lagoons, Thau, Berre and Bages-Sigean, which harbour resident populations. The annual cycles showed a common univoltine pattern in all lagoons where the presence of pelagic stages in the water column lasted ∼8 months. Field observations showed a release of ephyrae in winter time followed by pronounced growth between April and July, when individuals reached the largest sizes, before disappearing from the water column. Maximum abundance of ephyrae and medusae were registered in Thau. Medusae abundance attained a maximum of 331 ind 100 m-3 in Thau, 18 ind 100 m-3 in Berre and 7 ind 100 m-3 in Bages-Sigean lagoons. Temperature and zooplankton abundance appeared as leading factors of growth, where Bages-Sigean showed the population with higher growth rates (2.66 mm day-1) and maximum size (32 cm), followed by Thau (0.57-2.56 mm day-1; 22.4 cm) and Berre (1.57-2.22 mm day-1; 17 cm). The quantification of environmental windows used by the species showed wider ranges than previously reported in the Mediterranean Sea, which suggests a wide ecological plasticity of Aurelia spp. populations in north-western Mediterranean lagoons.

Published
2015
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34. A new transportable floating mesocosm platform with autonomous sensors for real-time data acquisition and transmission for studying the pelagic food web functioning

Author

Mostajir, Behzad, Le Floc'h, Emilie, Mas, Sébastien, Pete, Romain, Parin, David, Nouguier, Jean, Fouilland, Eric, Vidussi, Francesca, MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD), Observatoire de REcherche Méditerranéen de l'Environnement (OSU OREME), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut des Sciences de la MER de Rimouski (ISMER), Université du Québec à Rimouski (UQAR), Ecologie des systèmes marins côtiers (Ecosym), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Centre National de la Recherche Scientifique (CNRS), Centre d'Ecologie marine expérimentale (MEDIMEER), Université Montpellier 2 - Sciences et Techniques (UM2)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Montpellier 2 - Sciences et Techniques (UM2), and Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université Montpellier 1 (UM1)

Subjects
[SDE.BE]Environmental Sciences/Biodiversity and Ecology, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2013
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35. Bacterial carbon dependence on freshly produced phytoplankton exudates under different nutrient availability and grazing pressure conditions in coastal marine waters

Author

Fouilland, Eric, primary, Tolosa, Imma, additional, Bonnet, Delphine, additional, Bouvier, Corinne, additional, Bouvier, Thierry, additional, Bouvy, Marc, additional, Got, Patrice, additional, Le Floc'h, Emilie, additional, Mostajir, Behzad, additional, Roques, Cécile, additional, Sempéré, Richard, additional, Sime-Ngando, Télesphore, additional, and Vidussi, Francesca, additional

Published
2013
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39. An automatic device for in vivoabsorption spectra acquisition and chlorophyll estimation in phytoplankton cultures

Author

Le Floc'h, Emilie, Malara, Gilbert, and Sciandra, Antoine

Abstract

In order to aid the study of photoacclimation, a new programmable deviceis described which provides automatic on-line acquisition of in vivocellabsorption in phytoplankton cultures. The system was used for a long-termstudy of Rhodomonas salinagrown at constant photon flux density ina nitrate-limited continuous culture with different dilution rates. Particulate absorption measured at the red chlorophyll a(Chl a)maximum was not a good proxy of biomass, because of the large variabilityof cellular chlorophyll induced by nitrogen limitation. However, thedevice is well suited to automatic assessment of Chl aandphycoerythrin (PE) concentrations in phytoplankton cultures, if algal cellsize and concentration are measured in parallel to correct the packagingeffect. The effects of nitrogen limitation on Chl aand PE contentsand particle absorbance are discussed.

Published
2002
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40. Bacterial carbon dependence on freshly produced phytoplankton exudates under different nutrient availability and grazing pressure conditions in coastal marine waters.

Author

Fouilland E, Tolosa I, Bonnet D, Bouvier C, Bouvier T, Bouvy M, Got P, Le Floc'h E, Mostajir B, Roques C, Sempéré R, Sime-Ngando T, and Vidussi F

Subjects
Biomass, Carbon Isotopes analysis, Food Chain, France, Lipids analysis, Mediterranean Sea, Phytoplankton chemistry, Seasons, Seawater chemistry, Bacteria metabolism, Carbon metabolism, Heterotrophic Processes, Phytoplankton growth & development, Seawater microbiology
Abstract

The effects of grazing pressure and inorganic nutrient availability on the direct carbon transfer from freshly produced phytoplankton exudates to heterotrophic bacteria biomass production were studied in Mediterranean coastal waters. The short-term incorporation of ¹³C (H¹³CO₃) in phytoplankton and bacterial lipid biomarkers was measured as well as the total bacterial carbon production (BP), viral lysis and the microbial community structure under three experimental conditions: (1) High inorganic Nutrient and High Grazing (HN + HG), (2) High inorganic Nutrient and Low Grazing (HN + LG) and (3) under natural in situ conditions with Low inorganic Nutrient and High Grazing (LN + HG) during spring. Under phytoplankton bloom conditions (HN + LG), the bacterial use of freshly produced phytoplankton exudates as a source of carbon, estimated from ¹³C enrichment of bacterial lipids, contributed more than half of the total bacterial production. However, under conditions of high grazing pressure on phytoplankton with or without the addition of inorganic nutrients (HN + HG and LN + HG), the ¹³C enrichment of bacterial lipids was low compared with the high total bacterial production. BP therefore seems to depend mainly on freshly produced phytoplankton exudates during the early phase of phytoplankton bloom period. However, BP seems mainly relying on recycled carbon from viral lysis and predators under high grazing pressure.

Published
2014
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41. Toxicity of benz(a)anthracene and fluoranthene to marine phytoplankton in culture: does cell size really matter?

Author

Ben Othman H, Leboulanger C, Le Floc'h E, Mabrouk HH, and Hlaili AS

Subjects
Analysis of Variance, Biomass, Chlorophyll biosynthesis, Chlorophyll A, Fluorescence, Gas Chromatography-Mass Spectrometry, Lethal Dose 50, Photochemistry, Photosynthesis drug effects, Solutions, Species Specificity, Benz(a)Anthracenes toxicity, Cell Size, Fluorenes toxicity, Phytoplankton drug effects, Phytoplankton ultrastructure
Abstract

The toxicity of benz(a)anthracene and fluoranthene (polycyclic aromatic hydrocarbons, PAHs) was evaluated on seven species of marine algae in culture belonging to pico-, nano-, and microphytoplankton, exposed to increasing concentrations of up to 2 mg L(-1). The short-term (24h) toxicity was assessed using chlorophyll a fluorescence transients, linked to photosynthetic parameters. The maximum quantum yield Fv/Fm was lower at the highest concentrations tested and the toxicity thresholds were species-dependent. For acute effects, fluoranthene was more toxic than benz(a)anthracene, with LOECs of 50.6 and 186 μg L(-1), respectively. After 72 h exposure, there was a dose-dependent decrease in cell density, fluoranthene being more toxic than benz(a)anthracene. The population endpoint at 72 h was affected to a greater extent than the photosynthetic endpoint at 24h. EC50 was evaluated using the Hill model, and species sensitivity was negatively correlated to cell biovolume. The largest species tested, the dinoflagellate Alexandrium catenella, was almost insensitive to either PAH. The population endpoint EC50s for fluoranthene varied from 54 μg L(-1) for the picophytoplankton Picochlorum sp. to 418 μg L(-1) for the larger diatom Chaetoceros muelleri. The size/sensitivity relationship is proposed as a useful model when there is a lack of ecotoxicological data on hazardous chemicals, especially in marine microorganisms., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Published
2012
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