Laboratoire Des Science Of Lenvironnement Marin Lemar
Laboratoire Des Science Of Lenvironnement Marin Lemar
Farcy E.,French Research Institute for Exploitation of the Sea |
Burgeot T.,French Research Institute for Exploitation of the Sea |
Haberkorn H.,Laboratoire Des Science Of Lenvironnement Marin Lemar |
Auffret M.,Laboratoire Des Science Of Lenvironnement Marin Lemar |
And 9 more authors.
Environmental Science and Pollution Research | Year: 2013
Estuarine areas represent complex and highly changing environments at the interface between freshwater and marine aquatic ecosystems. Therefore, the aquatic organisms living in estuaries have to face highly variable environmental conditions. The aim of this work was to study the influence of environmental changes from either natural or anthropogenic origins on the physiological responses of Mytilus edulis. Mussels were collected in the Vilaine estuary during early summer because this season represents a critical period of active reproduction in mussels and of increased anthropogenic inputs from agricultural and boating activities into the estuary. The physiological status of the mussel M. edulis was evaluated through measurements of a suite of biomarkers related to: oxidative stress (catalase, malondialdehyde), detoxication (benzopyrene hydroxylase, carboxylesterase), neurotoxicity (acetylcholinesterase), reproductive cycle (vitelline, condition index, maturation stages), immunotoxicity (hemocyte concentration, granulocyte percentage, phagocytosis, reactive oxygen species production, oxidative burst), and general physiological stress (lysosomal stability). A selection of relevant organic contaminant (pesticides, (polycyclic aromatic hydrocarbons, polychlorobiphenyls) was measured as well as environmental parameters (water temperature, salinity, total suspended solids, turbidity, chlorophyll a, pheopigments) and mussel phycotoxin contamination. Two locations differently exposed to the plume of the Vilaine River were compared. Both temporal and inter-site variations of these biomarkers were studied. Our results show that reproduction cycle and environmental parameters such as temperature, organic ontaminants, and algal blooms could strongly influence the biomarker responses. These observations highlight the necessity to conduct integrated environmental approaches in order to better understand the causes of biomarker variations. © 2012 Springer-Verlag Berlin Heidelberg.
Fanfard S.,Laboratoire dEcogeochimie des Environnements Benthiques |
Charles F.,Laboratoire dEcogeochimie des Environnements Benthiques |
Coston-Guarini J.,Laboratoire Des Science Of Lenvironnement Marin Lemar |
Nozais C.,University of Quebec at Rimouski |
And 2 more authors.
Community Ecology | Year: 2016
The ecological process of community assembly is described as the succession of three phases: colonization, regulation and segregation. Early colonization remains the least studied and quantified phase of assembly. In order to fill this gap, an approach combining in situ experiments and modelling was proposed to study colonization by a benthic macrofauna community in open microcosms containing a single, non-limiting resource. The experiment was three months long. A total of 51 taxa were observed in the microcosms, but data analyses of the species composition and abundances revealed that five species, Capitella spp., Gammaropsis maculata, Erichtionus punctatus, Nereiphylla paretti and Harmothoe mariannae, explained most of the observed variation in the assembly process. The population dynamics of these species were simulated taking into account functional traits that govern individual interactions. The dynamic model simulated a demographic stochasticity due to low population densities that result from the small size of the experimental microcosms. Using this combined approach of experiments and modelling, we showed that predation interactions alone can account for the abundances and species composition of primary consumers during the transient phase of early colonization.[[ampi]copy;Akadémiai Kiadó, Budapest.
Whitby H.,Laboratoire Des Science Of Lenvironnement Marin Lemar |
Hollibaugh J.T.,University of Georgia |
van den Berg C.M.G.,University of Liverpool
Frontiers in Marine Science | Year: 2017
The concentrations of dissolved copper (Cud), copper-binding ligands, thiourea-type thiols, and humic substances (HSCu) were measured in estuarine waters adjacent to Sapelo Island, Georgia, USA, on a monthly basis from April to December 2014. Here we present the seasonal cycle of copper speciation within the estuary and compare it to the development of an annually occurring bloom of Ammonia Oxidizing Archaea (AOA), which require copper for many enzymes. Two types of complexing ligands (L1 and L2) were found to dominate with mean complex stabilities (log KCuL') of 14.5 and 12.8. Strong complexation resulted in lowering the concentration of free cupric ion (Cu2+) to femtomolar (fM) levels throughout the study and to sub-fM levels during the summer months. A Thaumarchaeota bloom during this period suggests that this organism manages to grow at very low Cu2+ concentrations. Correlation of the concentration of the L1 ligand class with a thiourea-type thiol and the L2 ligand class with HSCu provide an interesting dimension to the identity of the ligand classes. Due to the stronger complex stability, 82-99% of the copper was bound to L1. Thiourea-type thiols typically form Cu(I) species, which would suggest that up to ~90% copper could be present as Cu(I) in this region. In view of the very low concentration of free copper (pCu > 15 at the onset and during the bloom) and a reputedly high requirement for copper, it is likely that the Thaumarchaeota are able to access thiol-bound copper directly. © 2017 Whitby, Hollibaugh and van den Berg.
Lemaitre N.,Laboratoire Des Science Of Lenvironnement Marin Lemar |
Lemaitre N.,Vrije Universiteit Brussel |
Planquette H.,Laboratoire Des Science Of Lenvironnement Marin Lemar |
Dehairs F.,Vrije Universiteit Brussel |
And 14 more authors.
Deep-Sea Research Part I: Oceanographic Research Papers | Year: 2016
The Kerguelen Plateau is characterized by a naturally Fe-fertilized phytoplankton bloom that extends more than 1000 km downstream in the Antarctic Circumpolar Current. During the KEOPS2 study, in austral spring, we measured particulate nitrogen (PN), biogenic silica (BSi) and particulate iron (PFe) export fluxes in order to investigate how the natural fertilization impacts the stoichiometry and the magnitude of export fluxes and therefore the efficiency of the biological carbon pump. At 9 stations, we estimated elemental export fluxes based on element concentration to 234Th activity ratios for particulate material collected with in-situ pumps and 234Th export fluxes (Planchon et al., 2015). This study revealed that the natural Fe-fertilization increased export fluxes but to variable degrees. Export fluxes for the bloom impacted area were compared with those of a high-nutrient, low-chlorophyll (HNLC), low-productive reference site located to the south-west of Kerguelen and which had the lowest BSi and PFe export fluxes (2.55 mmol BSi m−2 d−1 and 1.92 µmol PFem−2 d−1) and amongst the lowest PN export flux (0.73 mmol PN m−2 d−1). The impact of the Fe fertilization was the greatest within a meander of the polar front (PF), to the east of Kerguelen, with fluxes reaching 1.26 mmol PN m−2 d−1; 20.4 mmol BSi m−2 d−1 and 22.4 µmol PFe m−2 d−1. A highly productive site above the Kerguelen Plateau, on the contrary, was less impacted by the fertilization with export fluxes reaching 0.72 mmol PN m−2 d−1; 4.50 mmol BSi m−2 d−1 and 21.4 µmol PFe m−2 d−1. Our results suggest that ecosystem features (i.e. type of diatom community) could play an important role in setting the magnitude of export fluxes of these elements. Indeed, for the PF meander, the moderate productivity was sustained by the presence of large and strongly silicified diatom species while at the higher productivity sites, smaller and slightly silicified diatoms dominated. Interestingly, our results suggest that PFe export fluxes can be driven by the lithogenic pool of particles, especially over the Plateau where such inputs from the sediments are important. Finally, for the Plateau and the PF meander, the comparison between PFe export and the particulate PFe stock integrated over the mixed layer depth revealed an efficient PFe export out of the mixed layer at these sites. Export efficiencies (i.e. the ratio between export and uptake) exhibit a very efficient silica pump especially at the HNLC reference station where heavily silicified diatoms were present. On the contrary, the increase with depth of the C:N ratio and the low nitrogen export efficiencies support the idea of a strong remineralization and nitrification activity. © 2016 Elsevier Ltd
Le Goic N.,Laboratoire Des Science Of Lenvironnement Marin Lemar |
Hegaret H.,Laboratoire Des Science Of Lenvironnement Marin Lemar |
Fabioux C.,Laboratoire Des Science Of Lenvironnement Marin Lemar |
Miner P.,French Research Institute for Exploitation of the Sea |
And 3 more authors.
Aquatic Living Resources | Year: 2013
The toxic dinoflagellate Alexandrium catenella recurrently blooms on the coasts of France and produces Paralytic Shellfish Toxins (PSTs) that accumulate in bivalves. These toxins can affect various physiological functions including reproduction. The present study aims to validate measurements of sperm viability, DNA content and mitochondrial membrane potential in Pacific oyster Crassostrea gigas using flow cytometry coupled with fluorescent markers, and to use these measurements to assess the cellular parameters of sperm from Pacific oysters exposed to A. catenella. These parameters may influence fertilization, embryogenesis and larval development in free-spawning shellfish. Sperm viability and DNA content estimation were assessed using SYBR-14, which only penetrates cells with intact membranes. Cell mortality was measured with propidium iodide (PI), which penetrates cells with membrane damage. Mitochondrial membrane potential, used as an estimate of mitochondrial function, was measured using JC-1 dye, which selectively enters into mitochondria and reversibly changes colour from green to orange as the membrane potential increases. To assess the effect of toxic algae on oyster sperm, broodstock (ripe oysters) were fed toxic (A. catenella) or non toxic (Heterocapsa triquetra) dinoflagellates at 250 cell ml-1 for 9 days. After this exposure period, mature oysters were stripped and cellular responses of sperm analysed. Average DNA staining, as measured by SYBR-14, appeared lower and more variable in gametes from A. catenella-exposed oysters than in those from control oysters fed H. triquetra. Additionally, mitochondrial membrane potential of sperm from A. catenella-exposed oysters was significantly higher (1.5 fold) than that of sperm produced by oysters fed H. triquetra. Both the increase of mitochondrial membrane potential and the modification of DNA structure can be expected to impact spermatozoa ability to fertilize oocytes and could thus impact related reproductive processes. © EDP Sciences, IFREMER, IRD 2013.
PubMed | Laboratoire Des Science Of Lenvironnement Marin Lemar
Type: Journal Article | Journal: Cytometry. Part A : the journal of the International Society for Analytical Cytology | Year: 2014
The Pacific oyster Crassostrea gigas accounts for a large part of shellfish aquaculture production worldwide. Aspects of morphological and functional characteristics of oyster oocytes remain poorly documented, and traditional techniques, such as microscopic observations of shape or fertilization rate, are time and space consuming. The purpose of this study was to assess for the first time viability and reactive oxygen species (ROS) production of Pacific oyster oocytes using flow cytometry (FCM) and to apply this method to determine oocyte responses to in vitro exposure to the toxic dinoflagellate Alexandrium minutum. A culture of A. minutum caused a significant increase in oocyte ROS production, which gradually increased with the age of the culture, but viability was not affected. Effect of the supernatant of the same A. minutum culture did not cause any significant modifications of oocyte morphology, viability, or ROS level. This study confirmed that some oocyte cellular characteristics can be assessed using FCM techniques.