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Publications
Publications (41)
Along with their important diversity, coastal ecosystems receive various amounts of nutrients, principally arising from the continent and from the related human activities (mainly industrial and agricultural activities). During the 20th century, nutrients loads have increased following the increase of both the global population and need of services...
The recent development of biological sensors has extended marine plankton studies from conducting laboratory bench work to in vivo and real-time observations. Flow cytometry (FCM) has shed new light on marine microorganisms since the 1980s through its single-cell approach and robust detection of the smallest cells. FCM records valuable optical prop...
Large amounts of nutrients have been released to the coastal ecosystems during the 20th century. Since then, management policies have been implemented and these amounts decreased in the economically developed countries. We examined the bi-decadal changes in nutrients (nitrate + nitrite, ammonium, orthophosphate and silicic acid) in the Arcachon bay...
datasets of phytoplankton species counts along the french littoral
MSFD). They are addressed under the D1C6 criterion, stating “the condition of the habitat type, including its biotic and abiotic structure and its functions…, is not adversely affected due to anthropogenic pressures”. The evaluation of pelagic habitats status is challenged by the functional and structural characteristics of pelagic habitat diversit...
Pelagic habitats are a policy priority below Descriptor 1 (Biodiversity) of the Marine Strategy Framework Directive
(MSFD). They are addressed under the D1C6 criterion, stating “the condition of the habitat type, including its
biotic and abiotic structure and its functions…, is not adversely affected due to anthropogenic pressures”. The
evaluation...
Coastal marine ecosystems, which play a crucial role in the biogeochemical and ecological functioning of the Earth, are highly sensitive to the combined effects of climate and human activities. Because of their location, coastal ecosystems are directly influenced by human activities, but it remains challenging to assess the spatial and temporal sca...
Adaptation of cell populations to environmental changes is mediated by phenotypic variability at the single-cell level. Enzyme activity is a key factor in cell phenotype and the expression of the alkaline phosphatase activity (APA) is a fundamental phytoplankton strategy for maintaining growth under phosphate-limited conditions. Our aim was to comp...
Marine mucilage has been described as worldwide phenomena occurring sporadically, or frequently in certain coastal areas. They are transitory phenomena that can remain in the photic zone for several days or weeks. Their occurrence has been more frequent and persistent, and their magnitude has increased during the last decades. Their formation typic...
Plankton produces numerous chemical compounds used in cosmetics and functional foods. They also play a key role in the carbon budget on the Earth. In a context of global change, it becomes important to understand the physiological response of these microorganisms to changing environmental conditions. Their adaptations and the response to specific e...
One way for phytoplankton to survive to orthophosphate depletion is to utilize the dissolved organic phosphorus by expressing alkaline phosphatase. The actual methods to assay the alkaline phosphate activity - either in bulk or as a presence-absence of enzyme activity - fail to provide information on individual living cells. In this context, we dev...
Harmful algal blooms (HABs) occur worldwide, causing health problems and economic damages to fisheries and tourism. Monitoring agencies are therefore essential, yet monitoring is based only on time-consuming light microscopy, a level at which a correct identification can be limited by insufficient morphological characters. The project MIDTAL (Micro...
A l'échelle du Golfe de Gascogne et de ses zones côtières et littorales, les suivis de la biodiversité montrent d'importantes variations annuelles d'abondance et de répartition géographique des espèces en relation avec le climat. Ces évolutions font apparaître des phases brutales d'accélération en relation avec des variations de même forçages clima...
A l'échelle du golfe de Gascogne et de ses zones côtières et littorales, les suivis de la biodiversité montrent d'importantes variations annuelles d'abondance e de répartition géographique des espèces en relation avec le climat. Les tendances actuelles montrent que la biodiversité va évoluer vers une augmentation de représentativité des espèces tem...
Microalgae worldwide regularly cause harmful effects, considered from the human perspective, in that they cause health problems and economic damage to fisheries and tourism. Cyanobacteria cause similar problems in freshwaters. These episodes encompass a broad range of phenomena collectively referred to as "harmful algal blooms" (HABs). For adequate...
The structure and functioning of the food web in Arcachon Bay (Bay of Biscay, Northeast Atlantic Ocean) was analyzed during the spring bloom period to evaluate the sensitivity of this ecologically and economically important ecosystem perturbation. Differences in the timing of the peaks in phytoplankton and zooplankton populations occur due to a mis...
As agents of mortality, viruses and nanoflagellates impact on picoplankton populations. We examined the differences in interactions between these compartments in two French Atlantic bays. Microbes, considered here as central actors of the planktonic food web, were first monitored seasonally in Arcachon (2005) and Marennes-Oléron (2006) bays. Their...
Seasonal and spatial variations of phytoplankton primary production were studied using a high frequency sampling strategy in the external (ENW) and internal (INW) part of Arcachon Bay, during 2002 and 2003. In order to better assess the availability of nutrients and their relationship with phytoplankton primary production, nutrient variability was...
Phytoplankton dynamics were assessed in the macrotidal ecosystem of Arcachon Bay through high-frequency surveys over a 5-year period in order to characterize typology of environmental conditions at the onset of the productive period. Temporal variations of hydrological and biological parameters were examined in external and internal waters of the l...
The robustness and sensitivities of different polarization-transfer methods that exploit heteronuclear dipole-dipole couplings are compared for a series of heterogeneous solid systems, including polycrystalline tetrakis(trimethylsilyl)silane (TKS), adamantane, a physical mixture of doubly (13)C,(15)N-enriched and singly (13)C-enriched polycrystalli...
Measurement of biogenic silica (BSi) in the suspended matter of estuarine and coastal waters is not trivial because of the interference of lithogenic silica (LSi) that can represent up to 90% or more of the total particulate silica within the water column. Till date, no method has provided a satisfying way to correct this mineral interference when...
We present the first in vivo study of diatoms using atomic force microscopy (AFM). Three chain-forming, benthic freshwater species -Eunotia sudetica, Navicula seminulum and a yet unidentified species - are directly imaged while growing on glass slides. Using the AFM, we imaged the topography of the diatom frustules at the nanometre range scale and...
Diatoms, one of the most productive phytoplankton groups in the ocean, have an essential requirement for silicic acid for the construction of their opaline shells. In seawater, silicic acid is present in three chemical species (H4SiO4, H3SiO4−, and H2SiO42−). The silicic acid molecule actually taken up by diatoms is still under discussion. Algal ce...
Results of past studies of the pH-dependent Si uptake kinetics of Phaeodactylum tricornutum Bohlin suggested that the anion SiO(OH) is the chemical form of dissolved Si taken up by marine diatoms. We determined the chemical form of Si taken up by three other marine diatom species and P. tricornutum by examining the kinetics of Si use under two dram...
Most state of the art adhesives fail to bond under wet conditions. Therefore, knowledge of the intrinsic properties of natural adhesives might give valuable information for future engineering approaches. This work investigates the adhesive that Eunotia sudetica, a species of benthic freshwater diatoms, produces to attach itself to a substrate. Atom...
Biological silica production has drawn intense attention and several molecules involved in biosilicification have been identified. Cellular mechanisms, however, remain unknown mainly due to the lack of probes required for obtaining information on live specimens.
The fluorescence spectra of the compound 2-(4-pyridyl)-5-((4-(2-dimethylaminoethylamino...
The chemical factors (inorganic nitrogen, phosphate, silicic acid) that potentially or actually control primary production were determined for the Bay of Brest, France, a macrotidal ecosystem submitted to high-nitrate-loaded freshwater inputs (winter nitrate freshwater concentrations >700 µM, Si:N molar ratio as low as 0.2, i.e. among the lowest ev...
To assess the consequences of very-high-nitrate freshwater inputs on phytoplankton community structure a complete 1993-1994 annual cycle is described for the Bay of Brest (France). In contrast to other nitrate-enriched coastal ecosystems where small and non-siliceous species dominate in summer, in this well-mixed macrotidal ecosystem diatoms >10 µ...
The Bay of Brest is a semi-enclosed coastal ecosystem receiving high nutrients loading from freshwater inputs. In order to analyse the response of phytoplankton stocks to increasing eutrophic conditions, a survey of the annual cycle of hydrographic properties, nutrients and chlorophyll a concentrations, and carbon uptake rates was performed at four...
Tréguer P., Nelson D.M. and Del Amo
Afin d'analyser la réponse de l'écosystème "Rade de Brest" à l'enrichissement du milieu, un suivi du cycle des concentrations en sels nutritifs et en chlorophylle a été réalisé en 1993 et ces résultats ont été comparés à des études antérieures. Bien que les apports de nitrates aient doublé en 20 ans, occasionnant une diminution des ratios Si/N, les...
The Bay of Brest, France, a typical semi-enclosed coastal ecosystem (159 km2) of western Europe, was studied during spring 1992 with respect to the biogeochemical cycle of silicon. Three periods of nutrient and phytoplankton dynamics (chlorophyll a, biogenic silica, species composition), were distinguished during spring 1992, each corresponding, re...
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Projects
Projects (4)
CocoriCO2 is an interdisciplinary project which aims to increase resilience, sustainability and competitiveness of the French shellfish industry, considering environmental risks and more particularly ocean acidification. It is funded by the European Maritime and Fisheries Fund (EMFF) for a total amount of 1.5 M€. To achieve this objective, we propose an innovative partnership between ecologists specialized in shellfish and environment interactions (IFREMER), biogeochemists recognized for their work on ocean acidification (CNRS), representatives of the sector at the national (CNC) and regional levels (CRC Bretagne Nord and Méditerranée) involved in the implementation and monitoring of the project. The project is based on several complementary disciplines, i.e. ecology, bio-geochemistry, physiology, economics and social sciences, well covered by the partnership. The specific objectives of the project consist in observing, analyzing, anticipating and remedying the effects of environmental changes (seawater acidification and warming) on shellfish farming in order to assess the vulnerability of ecosystems, farmed species and businesses to environmental change and more particularly the risk of "acidification". These four operations consist of:
1. observing the natural variability of the seawater pH (acidity) at high frequency over ten production basins representative of the shellfish sector (bays and estuaries, lagoons and nurseries), in relation to other parameters of the carbonate chemistry and the environment,
2. analyzing the impacts of acidification and warming on the growth of the most cultivated bivalves in France (oysters and mussels) during a complete life cycle in a farming situation,
3. anticipating the impacts of acidification and warming on the economy of the shellfish farming sector by integrating the adaptive capacities and the vulnerability of ecosystems and business,
4. remedying the effects of ocean acidification by testing re-vegetation and alkalizing techniques.
This project aimed to 1) quantify particulate organic matter (POM) composition, 2) determine its variation at different spatial (intra- to multi-system) and temporal (seasonal, interanual) scales, 3) identify the forcings (environmental/anthropogenic origin) to POM composition and variability and 4) investigate the link between POM composition and the bacterial compartment, within French coastal systems.
This project was based on data, logistic and infrastructure of the national network 'Service d'Observation en Milieu LITtoral' (SOMLIT, INSU) and on complementary sampling campaigns.
