Dynamics of exopolymeric carbon pools in relation with phytoplankton succession along the salinity gradient of a temperate estuary (France)

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