@article {8534, title = {Chlordecone-contaminated epilithic biofilms show increased adsorption capacities}, journal = {Science of The Total Environment}, volume = {825}, year = {2022}, month = {Jan-06-2022}, pages = {153942}, issn = {00489697}, doi = {10.1016/j.scitotenv.2022.153942}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0048969722010348}, author = {C{\'e}dric Hubas and Monti, Dominique and Jean-Michel Mortillaro and Augagneur, Sylvie and Carbon, Anne and Duran, Robert and Karama, Solange and Tarik Meziane and Pardon, Patrick and Risser, Th{\'e}o and Tapie, Nathalie and Najet Thiney and Budzinski, H{\'e}l{\`e}ne and Lauga, B{\'e}atrice} } @article {8845, title = {Contrasting organic matter composition in pristine and eutrophicated mangroves revealed by fatty acids and stable isotopes (Rio de Janeiro, Brazil)}, journal = {Estuarine, Coastal and Shelf Science}, year = {2022}, month = {Jan-09-2022}, pages = {108061}, abstract = {Mangrove sediments have a high capacity of carbon storage, as the result of larger organic matter (OM) inputs from mangrove trees (litter fall and fine roots production) than OM microbial degradation and export to coastal waters. Mangrove sediments also act as traps for suspended matter and particulate OM (POM) from surrounding water masses. Fatty acids (FAs) markers, δ13C and δ15N signatures were used here to characterize the OM composition in three mangroves located in three coastal embayments of the Rio de Janeiro state (Brazil) with increasing urbanization from a pristine mangrove M1 to a moderately impacted mangrove M2 and a highly impacted mangrove M3. In these mangroves, the δ15N signature of tree leaves and sediments increases with anthropogenic influence, consistent with a large-scale eutrophication gradient along the three regions. At mangrove M1, predominant OM inputs from mangrove trees are highlighted by high proportions of long-chain fatty acids, particularly in the inland station, where high organic carbon concentrations (126\ {\textpm}\ 108\ mg\ g-1) indicate limited sedimentation of mineral particles and high carbon storage capacities. The sedimentary OM of M3 mangrove was more labile as confirmed by the higher proportions of algal fatty acids, enriched δ13C signature and the C/N ratio 1.6 times lower (p\ \<\ 0.001) than in the pristine mangrove M1. At the M2 mangrove site, high contribution of bacterial FAs (around 20\%) to sedimentary OM and high proportion of poorly biodegradable saturated fatty acids suggest that bacteria degrade algal labile OM in surface sediments but do not mineralize the most refractory fraction of OM. At the eutrophic M3 site, our findings suggest that deposition of labile POM induced an increase of fungal biomass on the sediment, apparently enhancing the microbial loop, and potentially leading to mineralization of refractory OM and carbon losses through a priming effect.}, issn = {02727714}, doi = {10.1016/j.ecss.2022.108061}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0272771422003195}, author = {Chynel, Mathias and Rockomanovic, Sofia and Gwena{\"e}l Abril and Barroso, Glenda and Marotta, Humberto and Machado, Wilson and Sanders, Christian J. and Najet Thiney and Tarik Meziane} } @article {7060, title = {Functional kleptoplasts intermediate incorporation of carbon and nitrogen in cells of the Sacoglossa sea slug Elysia viridis}, journal = {Scientific Reports}, volume = {10}, year = {2020}, month = {Jan-12-2020}, abstract = {Some sacoglossan sea slugs incorporate intracellular functional algal chloroplasts, a process termed kleptoplasty. {\textquotedblleft}Stolen{\textquotedblright} chloroplasts (kleptoplasts) can remain photosynthetically active up to several months, contributing to animal nutrition. Whether this contribution occurs by means of translocation of photosynthesis-derived metabolites from functional kleptoplasts to the animal host or by simple digestion of such organelles remains controversial. Imaging of\ 13C and\ 15N assimilation over a 12-h incubation period of\ Elysia viridis\ sea slugs showed a light-dependent incorporation of carbon and nitrogen, observed first in digestive tubules and followed by a rapid accumulation into chloroplast-free organs. Furthermore, this work revealed the presence of\ 13C-labeled long-chain fatty acids (FA) typical of marine invertebrates, such as arachidonic (20:4n-6) and adrenic (22:4n-6) acids. The time frame and level of\ 13C- and\ 15N-labeling in chloroplast-free organs indicate that photosynthesis-derived primary metabolites were made available to the host through functional kleptoplasts. The presence of specific\ 13C-labeled long-chain FA, absent from\ E. viridis\ algal food, indicates animal based-elongation using kleptoplast-derived FA precursors. Finally, carbon and nitrogen were incorporated in organs and tissues involved in reproductive functions (albumin gland and gonadal follicles), implying a putative role of kleptoplast photosynthesis in the reproductive fitness of the animal host.}, doi = {10.1038/s41598-020-66909-7}, url = {http://www.nature.com/articles/s41598-020-66909-7}, author = {Cruz, S{\'o}nia and LeKieffre, Charlotte and Cartaxana, Paulo and C{\'e}dric Hubas and Najet Thiney and Jakobsen, Sofie and Escrig, St{\'e}phane and Bruno Jesus and K{\"u}hl, Michael and Calado, Ricardo and Meibom, Anders} } @article {7122, title = {Laminariales Host Does Impact Lipid Temperature Trajectories of the Fungal Endophyte Paradendryphiella salina (Sutherland.)}, journal = {Marine Drugs}, volume = {18}, year = {2020}, pages = {379}, abstract = {Kelps are colonized by a wide range of microbial symbionts. Among them, endophytic fungi remain poorly studied, but recent studies evidenced yet their high diversity and their central role in algal defense against various pathogens. Thus, studying the metabolic expressions of kelp endophytes under different conditions is important to have a better understanding of their impacts on host performance. In this context, fatty acid composition is essential to a given algae fitness and of interest to food web studies either to measure its nutritional quality or to infer about its contribution to consumers diets. In the present study,\ Paradendryphiella salina, a fungal endophyte was isolated from\ Saccharina latissima\ (L.) and\ Laminaria digitata\ (Hudson.) and its fatty acid composition was assessed at increasing salinity and temperature conditions. Results showed that fungal composition in terms of fatty acids displayed algal-dependent trajectories in response to temperature increase. This highlights that C18 unsaturated fatty acids are key components in the host-dependant acclimation of\ P. salina\ to salinity and temperature changes}, keywords = {fatty acids, fungal endophytes, laminariales, Paradendryphiella salina}, doi = {10.3390/md18080379}, url = {https://www.mdpi.com/1660-3397/18/8/379}, author = {Vallet, Marine and Tarik Meziane and Najet Thiney and Prado, Soizic and C{\'e}dric Hubas} } @article {5984, title = {Short-term changes in the quality of suspended particulate matter in a human impacted and mangrove dominated tropical estuary (Can Gio, Vietnam)}, journal = {Continental Shelf Research }, volume = {178}, year = {2019}, month = {01/05/2019}, pages = {59-67}, abstract = {

Suspended particulate matter (SPM) is a key component of coastal food webs and a key variable of nutrient budgets. Understanding its variability across short time scales in estuaries may help ecologists understand seasonal and diurnal migration of estuarine organisms, and answer how their nutritional requirements are fulfilled. It may also inform biogeochemists regarding the factors that influence import and export of nutrients between terrestrial and coastal ecosystems. This study aimed to link the dynamics of fatty acids, stable isotopes (δ13C and δ15N) and C/N ratios of SPM, revealing organic matter quality, to rapidly varying factors (SPM concentration, salinity and presence of daylight) and comparing this variability to the seasonal variation induced by the alternation of dry and wet seasons in the studied region. Our results revealed that these rapidly varying factors had a strong influence on the bacterial and the phytoplanktonic compartments of SPM. They suggest that tidally resuspended particles are the site of intense heterotrophic activity and that estuarine phytoplankton store lipids during the daytime up to substantially modifying SPM quality. Our study also shows higher freshness of SPM during the wet season. We expect this study to raise the interest of both biologists and biogeochemists to introduce daily variability of SPM in food webs and nutrient budgets modelling.

}, doi = {10.1016/j.csr.2019.03.011}, author = {Frank David and Cyril Marchand and Najet Thiney and Tran-thi, N and Tarik Meziane} } @article {5153, title = {{A nanoscale study of carbon and nitrogen fluxes in mats of purple sulfur bacteria: implications for carbon cycling at the surface of coastal sediments}}, journal = {Frontiers in Microbiology}, volume = {8}, year = {2017}, pages = {1995}, abstract = {

Mass blooms of purple sulfur bacteria growing seasonally on green stranded macroalgae have a major impact on the microbial composition and functionality of intertidal mats. To explore the active anoxygenic phototrophic community in purple bacterial mats from the Roscoff Aber Bay (Brittany, France), we conducted a combined approach including molecular and high-resolution secondary ion mass spectrometry (NanoSIMS) analyses. To investigate the dynamics of carbon and nitrogen assimilation activities, NanoSIMS was coupled with a stable isotope probing (SIP) experiment and a compound specific isotope analysis (CSIA) of fatty acid methyl ester (FAME). Sediment samples were incubated with 13C- and/or 15N-labelled acetate, pyruvate, bicarbonate and ammonium. NanoSIMS analysis of 13C - and 15N -incubated samples showed elevated incorporations of 13C - and 15N in the light and of 13C -acetate in the dark into dense populations of spherical cells that unambiguously dominated the mats. These results confirmed CSIA data that ranked vaccenic acid, an unambiguous marker of purple sulfur bacteria, as the most strongly enriched in the light after 13C -acetate amendment and indicated that acetate uptake, the most active in the mat, was not light-dependent. Analysis of DNA- and cDNA-derived pufM gene sequences revealed that Thiohalocapsa-related clones dominated both libraries and were the most photosynthetically active members of the mat samples. This study provides novel insights into the contribution of purple sulfur bacteria to the carbon cycle during their seasonal developments at the sediment surface in the intertidal zone.

}, doi = {10.3389/fmicb.2017.01995}, url = {https://www.frontiersin.org/articles/10.3389/fmicb.2017.01995/abstract}, author = {C{\'e}dric Hubas and Boeuf, Dominique and Bruno Jesus and Najet Thiney and Bozec, Yann and Christian Jeanthon} } @article {4340, title = {The fate of C4 and C3 macrophyte carbon in central Amazon floodplain waters: Insights from a batch experiment}, journal = {Limnologica - Ecology and Management of Inland Waters}, volume = {59}, year = {2016}, pages = {90-98}, abstract = {

The central Amazon floodplains are particularly productive ecosystems, where a large diversity of organic carbon sources are available for aquatic organisms. Despite the fact that C4 macrophytes generally produce larger biomasses than C3 macrophytes, food webs in the central Amazon floodplains appear dominantly based on a C3 carbon source.

In order to investigate the respective fate and degradation patterns of C4 and C3 aquatic plant-derived material in central Amazon floodplains, we developed a 23-days batch experiment. Fatty acid and carbon concentrations as well as stable isotope compositions were monitored over time in 60\ L tanks. These tanks contained Amazon water, with different biomasses of C3 and C4 macrophyte, representative of in situ densities occurring in central Amazon floodplains.

In the C4Paspalum repens treatments, organic (POC, DOC) and inorganic carbon (DIC) got rapidly enriched in 13C, whereas in the C3Salvinia auriculata treatments, POC and DOC showed little change in concentration and isotopic composition, and DIC got depleted in 13C. The contribution of P. repens to POC and DOC was estimated to reach up to 94.2 and 70.7\%, respectively. In contrast, no differences were reported between the C3S. auriculata and control treatments, an observation attributed to the lower C3 biomass encountered in the field, to a slower degradation rate of C3 compared to C4 compounds, and to similar isotopic compositions for river POC and DOC, and C3 compounds.

The 13C enrichments of POC, DOC, and DIC from P. repens treatments were attributed to an enhanced bacterially-mediated hydrolysis and mineralization of C4 material. Evolutions of bacterial abundance and branched fatty acid concentrations confirmed the role of heterotrophic microbial communities in the high P. repens decomposition rate. Our experiment highlights the predominant role of C4 aquatic plants, as a large source of almost entirely biodegradable organic matter available for heterotrophic activity and CO2 outgassing to the atmosphere.

}, keywords = {Central amazon, Degradation, fatty acids, Floodplains, Macrophytes, Stables isotopes}, doi = {doi:10.1016/j.limno.2016.03.008}, author = {Jean-Michel Mortillaro and Passarelli, C and Gwena{\"e}l Abril and C{\'e}dric Hubas and Luis Felipe Artigas and Marc F Benedetti and Najet Thiney and Moreira-Turcq, P and P{\'e}rez, M A and Vidal, L and Tarik Meziane} } @article {3383, title = {Seasonal variations of the composition of microbial biofilms in sandy tidal flats: Focus of fatty acids, pigments and exopolymers}, journal = {Estuarine, Coastal and Shelf Science}, volume = {153}, year = {2015}, pages = {29 - 37}, abstract = {

Abstract Biofilms, or microbial mats, are common associations of microorganisms in tidal flats; they generally consist of a large diversity of organisms embedded in a matrix of Extracellular Polymeric Substances (EPS). These molecules are mainly composed of carbohydrates and proteins, but their detailed monomer compositions and seasonal variations are currently unknown. Yet this composition determines the numerous roles of biofilms in these systems. This study investigated the changes in composition of carbohydrates in intertidal microbial mats over a year to decipher seasonal variations in biofilms and in varying hydrodynamic conditions. This work also aimed to assess how these compositions are related to microbial assemblages. In this context, natural biofilms whose development was influenced or not by artificial structures mimicking polychaete tubes were sampled monthly for over a year in intertidal flats of the Chausey archipelago. Biofilms were compared through the analysis of their fatty acid and pigment contents, and the monosaccharide composition of their \{EPS\} carbohydrates. Carbohydrates from both colloidal and bound \{EPS\} contained mainly glucose and, to a lower extent, galactose and mannose but they showed significant differences in their detailed monosaccharide compositions. These two fractions displayed different seasonal evolution, even if glucose accumulated in both fractions in summer; bound \{EPS\} only were affected by artificial biogenic structures. Sediment composition in fatty acids and pigments showed that microbial communities were dominated by diatoms and heterotrophic bacteria. Their relative proportions, as well as those of other groups like cryptophytes, changed between times and treatments. The changes in \{EPS\} composition were not fully explained by modifications of microbial assemblages but also depended on the processes taking place in sediments and on environmental conditions. These variations of \{EPS\} compositions are likely to alter different ecosystem processes such as biostabilisation or pollutants trapping.

}, keywords = {biofilms, biogenic structures, EPS, fatty acids, monosaccharide composition, pigments}, issn = {0272-7714}, doi = {http://dx.doi.org/10.1016/j.ecss.2014.11.013}, url = {http://www.sciencedirect.com/science/article/pii/S0272771414003412}, author = {Passarelli, C and Tarik Meziane and Najet Thiney and Dominique Boeuf and B Jesus and Mickael Ruivo and Christian Jeanthon and C{\'e}dric Hubas} }