%0 Journal Article %J Aquatic Living Resources %D 2018 %T Cultured eastern oysters (Crassostrea virginica): retention and assimilation of picophytoplankton using a multi-biomarker approach %A Rémi Sonier %A Réjean Tremblay %A Frédéric Olivier %A Tarik Meziane %A Comeau, Luc Andre %K Aquaculture %K fatty acids %K Picophytoplankton %K Shellfish} %K Stable isotopes %K {Crassostrea virginica %X

{In this study, we investigated the food sources of eastern oysters Crassostrea virginica cultivated in Atlantic Canada. Stable isotopes (C-13 and N-15) and fatty acid biomarkers were used to identify these sources under in situ conditions for suspended (similar to 0.5 m below surface) and bottom(similar to 2 m) culture stocks. It was found that particulate organic matter represented the main food source, with major contributions from live phytoplankton. Higher lipid contents were detected in the digestive glands of suspended oysters compared to bottom oysters (p < 0.05). Bottom oysters did not show significant preference for detrital or bacterial organic matter. Near-surface waters contained an elevated picophytoplankton biomass (PPP, 0.2-2 mu m, 1.93 +/- 0.16mg l(-1), mean +/- SEM) compared to nanophytoplankton biomass (NPP, > 2 mu m, 1.05 +/- 0.15 mu g l(-1), mean +/- SEM). To determine whether the small size PPP was captured and assimilated by C. virginica, feeding trials were conducted in the laboratory using three PPP/NPP diets (20%, 50%, and 80% PPP), consisting of isotopically-labelled (delta C-13) PPP cells (Nannochloropsis oculata) and non-labelled NPP cells (Tisochrysis lutea). An isotopically-labelled fatty acids analysis indicated PPP assimilation in various tissues (digestive gland, gills, mantle, and abductor muscle), including from oysters fed the reduced (20%) PPP diet. Isotopic enrichment (C-13) in the FA 22:2 (non-methylene-interrupted or NMI) showed that precursors of NMIs utilized PPP carbon in its biosynthesis process. In conclusion, C. virginica assimilated primarily particulate organic matter (POM), including PPP, which dominated the phytoplankton community in near surface waters. C. virginica can exploit PPP carbon during fatty acid production and further biosynthesis.}

%B Aquatic Living Resources %V 30 %8 08/2018 %G eng %9 Article %R {10.1051/alr/2017031} %0 Journal Article %J Estuarine, Coastal and Shelf Science %D 2018 %T Dynamics of exopolymeric carbon pools in relation with phytoplankton succession along the salinity gradient of a temperate estuary (France) %A Morelle, Jérôme %A Mathilde Schapira %A Françoise, Sylvaine %A Courtay Gaëlle %A Francis Orvain %A Pascal Claquin %K Exopolymeric substances Species %K Nanophytoplankton %K Picophytoplankton %K richness %X

In parallel to phytoplankton community dynamics, transparent exopolymeric particles (TEP) and exopolymeric
substances (EPS) were investigated along the salinity gradient of a temperate estuary (Seine estuary, Normandy,
France) over the course of a year. The phytoplankton community was mainly dominated by marine diatom
species (especially Skeletonema sp., Nitzschia sp., and Paralia sulcata) associated with a spring bloom of picoeukaryotes
and the development of Cryptophyceae in summer. The decreases in species richness and salinity were
correlated along the estuary and a significant exponential relationship between species richness and primary
production was identified. Concentrations of TEP and EPS (soluble and bound carbohydrates) are highly dynamic
in this estuary and can reach respectively 69 mgC L−1, and 33 mgC L−1. TEP distribution was mainly
related to physical factors (hydrodynamics, maximum turbidity zone formation and sediment resuspension)
probably produced by stressed or dying phytoplankton, while EPS appeared to be excreted during the phytoplankton
spring bloom. Soluble and bound EPS appear to be related to Skeletonema sp. and Cryptophyceae occurrences.
This paper presents the dynamic pattern of these carbon pools, which play an important role in the
trophic network and influence the flocculation processes involved in the fate of both organic and inorganic
matter.

%B Estuarine, Coastal and Shelf Science %V 209 %P 18-29 %G eng