Phenolic fingerprint of the seagrass Posidonia oceanica from four locations in the Mediterranean Sea: first evidence for the large predominance of chicoric acid
Abstract The phenolic fingerprint of the leaves of Posidonia oceanica collected from four different Mediterranean Sea regions was determined using a panel of analytical techniques. It was found to be dominated by caffeic tartrates, along with low amounts of coumaric and ferulic tartrates. Chicoric acid (CA) was unambiguously identified as the major phenolic compound, regardless of the sample or collection site. Caftaric acid (CAF) was the second most abundant phenolic, but in much lower average concentrations. These results contrast with most of the previous works, in which CA was not even mentioned. The dramatic influence of extract handling, as well as the importance of choosing the adequate criteria of identity to standards, was demonstrated. These results show the importance of analyzing the crude extract to avoid some of the major pitfalls in determining the phenolic fingerprints. This is the first report to identify and quantify CAF in the Posidoniaceae and to identify CA as the dominant phenolic in Posidonia leaves. The large accumulation of CA in both living (10.12–12.78 mg g-1 dw) and detrital leaves (2.49–12.11 mg g-1 dw) across large geographical scales is noteworthy. The lack of significant concentrations of flavonoids contrasts with other seagrass genera. Importantly, the phenolic signature of P. oceanica shows significant similarities to those of Cymodocea nodosa and Syringodium filiforme, both belonging to the Cymodoceaceae. These results are discussed in terms of metabolic pathways and phylogenetic relationships.
(Botanica Marina. vol. 58, n° 0006-8055, pp. 379-391, 01/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Process-based modeling of cross-shore sandbar behavior
A coupled wave–current–sediment transport beach profile model is used to simulate cross-shore sandbar evolution on the time scale from days to months comprising both rapid offshore and slow onshore migrations. The discrimination of four modes of sediment transport driven by velocity and acceleration skewness, mean currents and slope effects allows addressing the dominant hydrodynamic processes governing cross-shore sandbar behavior. Acceleration–skewness-induced transport systematically results in a slow onshore sandbar migration together with a slow bar growth. Velocity–skewness-induced transport can drive onshore and offshore bar migrations with substantially larger rates. Mean–current-induced sediment transport systematically drives an offshore bar migration with either bar growth or decay. Slope effects essentially act as a damping term. The water level above the sandbar crest mainly influences the sandbar migration direction, while wave obliquity regulates the magnitude of the migration rates and is crucial to accurately simulate offshore sandbar migration during energetic obliquely incident waves. The inclusion of acceleration skewness is a necessary requirement to accurately reproduce the onshore migration of shallow sandbars. Detailed inter-site comparison of best-fit model parameters shows large differences meaning that free parameters attempt to compensate some mispecifications of the physics in the model. Although this also applies to other existing beach profile models, this suggests that this model needs further improvements including, for instance, the contribution of the injection of breaking wave turbulence onto the bed to sand stirring.
(Coastal Engineering. vol. 95, n° 0378-3839, pp. 35-50, 01/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Storm impact on the seasonal shoreline dynamics of a meso- to macrotidal open sandy beach (Biscarrosse, France)
A three-year dataset (2007-2010) of shoreline and sandbar positions derived from video observations of an open sandy beach (Biscarrosse, France) is analyzed, to explore the impact of storms on the seasonal shoreline dynamics. The results indicate that a clear seasonality is observed in the offshore significant wave height and in the occurrence of 'winter storm' events that are defined as periods with significant wave height greater than 4 m lasting at least 12 h. Data indicate that the range of variation of the inner sandbar positions (120 m) is two and a half times larger than the range of variation of the shoreline position. Correlation analyses suggest that the offshore conditions do not conclusively explain the position of the inner bar. Shoreline positions show a clear seasonal pattern, displaying a stable position occurring in February and July, providing evidence of seasonal-recovery although analysis of storm activity indicates that the number and intensity of storms is highly variable over the three years. The Biscarrosse data show that rapid erosion can be observed also under moderate conditions, and that beach recovery after the storm season can be relatively rapid.
(Geomorphology. vol. 228, n° 0169-555X, pp. 448-461, 01/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE
Cockle infection by Himasthla quissetensis – II. The theoretical effects of climate change
Numerous marine populations experience parasite pressure. This is the case of the cockles Cerastoderma edule which are often highly infected by trematode macroparasites. These parasites display a complex life cycle, with a succession of free-living and parasitic stages. Climate, and in particular temperature, is an important modulator of the transmission dynamics of parasites. Consequently, global change is thought to have implications for the epidemiology of infectious diseases. Using Himasthla quissetensis, a dominant parasite of cockles as 2nd intermediate host in Arcachon Bay (France), we used mathematical models of parasite emergence (cercariae) and parasite infection (metacercariae) in cockles as a function of water temperature, in order to study different scenarios of temperature increases. Globally, with a + 0.5 °C to + 6.0 °C simulation, cumulated emergence of cercariae and accumulation of metacercariae tended to decrease or stagnate, respectively. This is the consequence of a trade-off between sooner (spring) and later (autumn) cercariae emergence/infestation on one hand, and a longer inhibition period of cercariae emergence/infestation during the hottest days in summer. Using sea water temperature in Oualidia (Morocco) where mean annual sea temperature is 3 °C higher than in Arcachon Bay, our model predicted infestation all year long (no seasonality). The model gave a correct estimation of the total number of parasites that was expected in cockles. Conversely, observed infestation in Oualidia followed a seasonal pattern like in Arcachon Bay. These results suggest that, if temperature is a strong driver of parasite transmission, extrapolation in the framework of climate change should be performed with caution.
(Journal of Sea Research (JSR), n° 1385-1101, 01/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The toxic dinoflagellate Alexandrium minutum disrupts daily rhythmic activities at gene transcription, physiological and behavioral levels in the oyster Crassostrea gigas
The objective of the present work was to study the effect of the harmful alga Alexandrium minutum on the daily rhythm of the oyster Crassostrea gigas. Many metabolic and physiological functions are rhythmic in living animals. Their cycles are modeled in accordance with environmental cycles such as the day/night cycle, which are fundamental to increase the fitness of an organism in its environment. A disruption of rhythmic activities is known to possibly impact the health of an animal. This study focused in C. gigas, on a gene known to be involved in circadian rhythmicity, cryptochrome gene (CgCry), on putative clock-controlled genes involved in metabolic and physiological functions, on the length cycle of the style, a structure involved in digestion, and on the rhythmicity of valve activity involved in behavior. The results indicate that daily activity is synchronized at the gene level by light:dark cycles in C. gigas. A daily rhythm of valve activity and a difference in crystalline style length between scotophase and photophase were also demonstrated. Additionally, A. minutum exposure was shown to alter cyclic activities: in exposed oysters, gene transcription remained at a constant low level throughout a daily cycle, valve opening duration remained maximal and crystalline style length variation disappeared. The results show that a realistic bloom of A. minutum clearly can disrupt numerous and diverse molecular, physiological and behavioral functions via a loss of rhythmicity.
(Aquatic Toxicology. vol. 158, n° 0166-445X, pp. 41-49, 01/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS
The coccolithophores Emiliania huxleyi and Coccolithus pelagicus: Extant populations from the Norwegian–Iceland Seas and Fram Strait
The distributions of the coccolithophore species Emiliania huxleyi and Coccolithus pelagicus (heterococcolith-bearing phase) in the northern North Atlantic were investigated along two zonal transects crossing Fram Strait and the Norwegian–Iceland Sea, respectively, each conducted during both July 2011 and September–October 2007. Remote-sensing images as well as CTD and ARGO profiles were used to constrain the physico-chemical state of the surface water and surface mixed layer at the time of sampling. Strong seasonal differences in bulk coccolithophore standing stocks characterized the northern and southern transects, where the maximum values of 53×103 cells/l (fall) and 70×103 cells/l (summer), respectively, were essentially explained by E. huxleyi. This pattern confirms previous findings of a summer to fall northwestward shift in peak coccolithophore cell densities within the Nordic Seas. While depicting an overall zonal shift in high cell densities between the summer (Norwegian Sea) and fall (northern Iceland Sea) conditions, the southern transects were additionally characterized by local peak coccolithophore concentrations associated with a geographically and temporally restricted convective process (Lofoten Gyre, summer), as well as an island mass effect (in the vicinity of Jan Mayen Island, fall). Maximum coccolithophore abundances within Fram Strait were found during both seasons close to the western frontal zone (Polar and Arctic Fronts) an area of strong density gradients where physical and chemical properties of the surface mixed layer are prone to enhance phytoplankton biomass and productivity. Here, changes in species dominance from E. huxleyi in summer, to C. pelagicus in fall, were related to the strengthened influence during summer, of surface AW, as well as to high July solar irradiance, within an area usually characterized by C. pelagicus-dominated low density populations.
(Deep Sea Research Part I: Oceanographic Research Papers. vol. 98, n° 0967-0637, pp. 1-9, 26/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UiT
The most vagile host as the main determinant of population connectivity in marine macroparasites
Although molecular ecology of macroparasites is still in its infancy, general patterns are beginning to emerge, e.g. that the most vagile host in a complex life cycle is the main determinant of the population genetic structure of their parasites. This insight stems from the observation that populations of parasites with only freshwater hosts are more structured than those with terrestrial or airborne hosts. Until now, the same has not been tested for marine systems, where, in theory, a fully marine life cycle might sustain high dispersal rates because of the absence of obvious physical barriers in the sea. Here, we tested whether a marine trematode parasite that utilises migratory birds exhibited weaker population genetic structure than those whose life cycle utilises marine fish as the vagile host. Part of the mitochondrial cytochrome c oxidase 1 (COI) gene was sequenced from individual sporocysts from populations along the Atlantic coast of Europe and North Africa. Strong population structure (Φst = 0.25, p < 0.0001) was found in the fully marine trematode Bucephalus minimus (hosted by fish), while no significant structure (Φst = 0.015, p = 0.19257) was detected in Gymnophallus choledochus (hosted by birds). However, demographic models indicate recent colonisation rather than high dispersal as an alternative explanation of the low levels of structure observed in G. choledochus. Our study is the first to identify significant genetic population structure in a marine autogenic parasite, suggesting that connectivity between populations of marine parasites can be limited despite the general potential for high dispersal of their hosts in the marine environment.
(Marine Ecology Progress Series. vol. 520, n° 0171-8630, pp. 85-99, 26/10/2026)
NIOZ, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UM5, UCC
Atlas des diatomées des eaux douces de la Réunion
L’ile de la Réunion, de par son caractère insulaire et son isolement, présente de grandes particularités des assemblages biologiques, doublée d’un fort taux d’endémisme. Les diatomées des cours d’eau ne font pas exception à ce constat, et étaient fortement méconnues jusqu’à un passé récent. Or la connaissance des espèces présentes et de leur écologie est le premier pas pour leur protection face aux pollutions et aux pressions qui s’exercent sur leurs habitats. Un programme de recherche-développement financé par l’Office de l’Eau de la Réunion, la DEAL Réunion, le FEDER et l’ONEMA a été lancé à partir de 2008 et a duré jusqu’à fin 2013. Il a été conduit par le consortium Asconit-Cemagref (devenu depuis Irstea). Le but était d’identifier les espèces diatomiques locales, de les nommer, de leur affecter une écologie et une écologie de l’altération, de fonder un nouvel indice diatomique adapté à l’évaluation des cours d’eau de la Réunion (l’IDR) et de transférer cette nouvelle méthode avec la production des documents et outils d’accompagnement (guide méthodologique, guide taxonomique, outil de calcul sous R et sa notice d’utilisation etc. Au cours de ce programme, 343 taxons ont pu être identifiés ou reconnus à l’espèce, certains non trouvés dans la littérature taxonomique mondiale se voyant affecter un code de genre et un numéro d’espèce. Le présent Atlas taxonomique édité par l’Office de l’Eau de la Réunion contient un grand nombre de fiches-taxons décrivant la plupart de ces espèces locales, avec des indications morphologiques et des supports iconographiques au microscope optique et électronique permettant de les reconnaître et de les déterminer : des cartes chorologiques permettant de résumer à quels sites ou dans quels cours d’eau on les trouve, de façon différenciée aux deux saisons ; et enfin, des figurations permettant de situer et de résumer leurs caractéristiques autoécologiques par rapport à des variables abiotiques naturelles et à d’autres sous forte influence des altérations anthropiques.
(pp. 230, 26/10/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEFE, INEE-CNRS, CNRS, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse
Glacial ice and atmospheric forcing on the Mertz Glacier Polynya over the past 250 years
The Mertz Glacier Polynya off George V Land, East Antarctica, is a source of Adélie Land Bottom Water, which contributes up to B25% of the Antarctic Bottom Water. This major polynya is closely linked to the presence of the Mertz Glacier Tongue that traps pack ice upstream. In 2010, the Mertz Glacier calved a massive iceberg, deeply impacting local sea ice conditions and dense shelf water formation. Here we provide the first detailed 250-year long reconstruction of local sea ice and bottom water conditions. Spectral analysis of the data sets reveals large and abrupt changes in sea surface and bottom water conditions with a B70-year cyclicity, associated with the Mertz Glacier Tongue calving and regrowth dynamics. Geological data and atmospheric reanalysis, however, suggest that sea ice conditions in the polynya were also very sensitive to changes in surface winds in relation to the recent intensification of the Southern Annular Mode.
(Nature Communications. vol. 6, n° 2041-1723, pp. 6642, 26/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ULaval, INSU - CNRS, CNRS, LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, VOG, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, BTP, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS
Phytoplankton versus macrophyte contribution to primary production and biogeochemical cycles of a coastal mesotidal system. A modelling approach
This study presents an assessment of the contributions of various primary producers to the global annual production and N/P cycles of a coastal system, namely the Arcachon Bay, by means of a numerical model. This 3D model fully couples hydrodynamic with ecological processes and simulates nitrogen, silicon and phosphorus cycles as well as phytoplankton, macroalgae and seagrasses. Total annual production rates for the different components were calculated for different years (2005, 2007 and 2009) during a time period of drastic reduction in seagrass beds since 2005. The total demand of nitrogen and phosphorus was also calculated and discussed with regards to the riverine inputs. Moreover, this study presents the first estimation of particulate organic carbon export to the adjacent open ocean.
The calculated annual net production for the Arcachon Bay (except microphytobenthos, not included in the model) ranges between 22,850 and 35,300 tons of carbon. The main producers are seagrasses in all the years considered with a contribution ranging from 56% to 81% of global production. According to our model, the -30% reduction in seagrass bed surface between 2005 and 2007, led to an approximate 55% reduction in seagrass production, while during the same period of time, macroalgae and phytoplankton enhanced their productions by about +83% and +46% respectively. Nonetheless, the phytoplankton production remains about eightfold higher than the macroalgae production. Our results also highlight the importance of remineralisation inside the Bay, since riverine inputs only fulfill at maximum 73% nitrogen and 13% phosphorus demands during the years 2005, 2007 and 2009. Calculated advection allowed a rough estimate of the organic matter export: about 10% of the total production in the bay was exported, originating mainly from the seagrass compartment, since most of the labile organic matter was remineralised inside the bay.(Estuarine, Coastal and Shelf Science. vol. 165, n° 0272-7714, pp. 52-60, 26/10/2026)
IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS