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

Abstract

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 pico-eukaryotes 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. Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.

Organic Matter Composition of Biomineral Flocs and Its Influence on Suspended Particulate Matter Dynamics Along a Nearshore to Offshore Transect

“…Our seasonal pattern is in line with findings from the turbidity maximum of the Seine estuary (Morelle et al, 2018).…”

“…Measurements of TEP in combination with SPM concentration are scarce. So far published data reveal a seasonal variation, with high SPM concentration in winter, along with increased concentrations of OM, including TEP, displaying maxima within high turbid areas (Horemans et al., 2021; Malpezzi et al., 2013; Morelle et al., 2018). The SPM and TEP concentrations appear to be well correlated.…”

Carbon Dynamics Along the Seine River Network: Insight From a Coupled Estuarine/River Modeling Approach

“…One of the main controls of the biogeochemical dynamics of the Seine river network is the significant anthropic pressure which translates into large nutrients and organic matter point sources, in particular in Achères downstream the WWTP SAV and Rouen as was evidenced by Servais et al (1991), Romero et al (2016), and Marescaux et al (2018). Although the timing of the simulated phytoplankton bloom is late by a few weeks, the amplitude of the nutrient consumption is similar to observation and the decrease in dissolved silica confirms the domination of diatoms within phytoplankton biomass (Morelle et al, 2018;Garnier unpublished).…”

Organic Matter Composition of Biomineral Flocs and its Influence on Suspended Particulate Matter Dynamics along a Nearshore to Offshore Transect

“…Both the fresh and refractory OM can be associated to the mineral surfaces, being protected from microbial respiration (Chen et al, 2021;Hemingway et al, 2019;Kalbitz et al, 2005;Keil et al, 1994). The protected mineral-associated OM explains the high TEP concentrations in winter in high turbid areas such as the Belgian nearshore, Chesapeake Bay (Malpezzi et al, 2013) or the Seine estuary (Morelle et al, 2018).…”

“…Measurements of TEP in combination with SPM concentration are scarce. So far published data reveal a seasonal variation, with high SPM concentration in winter, along with increased concentrations of OM, including TEP, displaying maxima within high turbid areas (Horemans et al, 2021;Malpezzi et al, 2013;Morelle et al, 2018). The SPM and TEP concentrations appear to be well correlated.…”