Coupling between sediment biogeochemistry and phytoplankton development in a temperate freshwater marsh (Charente-Maritime, France): Evidence of temporal pattern

Raphaël Moncelon; Marie Gouazé; Philippe Pineau; Eric Bénéteau; Martine Bréret; Olivier Philippine; François-Xavier Robin; Christine Dupuy; Edouard Metzger

doi:10.1016/j.watres.2020.116567

Coupling between sediment biogeochemistry and phytoplankton development in a temperate freshwater marsh (Charente-Maritime, France): Evidence of temporal pattern

Water Res. 2021 Feb 1:189:116567. doi: 10.1016/j.watres.2020.116567. Epub 2020 Oct 25.

Authors

Raphaël Moncelon¹, Marie Gouazé², Philippe Pineau², Eric Bénéteau³, Martine Bréret², Olivier Philippine⁴, François-Xavier Robin⁴, Christine Dupuy², Edouard Metzger³

Affiliations

¹ Laboratoire LIENSs, UMR 6250, La Rochelle Université, Bâtiment ILE, 2 Rue Olympe de Gouges, La Rochelle, France. Electronic address: raphael.moncelon1@univ-lr.fr.
² Laboratoire LIENSs, UMR 6250, La Rochelle Université, Bâtiment ILE, 2 Rue Olympe de Gouges, La Rochelle, France.
³ LPG-BIAF, Bio-Indicateurs Actuels et Fossiles, UMR CNRS 6112, Université d'Angers, 2 Boulevard Lavoisier, 49045 Angers Cedex, France.
⁴ UNIMA, 28 rue Jacques de Vaucanso, ZI de Périgny, 17180 Périgny, France.

PMID: 33161327
DOI: 10.1016/j.watres.2020.116567

Abstract

In freshwater systems, sediment can be an important source for the internal loading of PO₄. The limiting character of this element in such system leads to consider this phenomenon in terms of eutrophication risks and water quality stakes. A four-months follow-up (January, March, April and May 2019) was carried out in a strong phosphate (PO₄) limited secondary channel from an artificial irrigation system of Charente Maritime (France) to link the mobilization of remineralization products in the upper 6 cm layer of sediment (conventional core slicing/centrifugation and DET probes) and the phytoplankton biomass dynamics in the water column. Results showed congruent patterns between the temporal succession of the organic matter mineralization processes in the sediment and the primary biomass dynamics in the water column. In January and March (considered in winter), PO₄ proved to be retained by adsorption onto iron oxides in anoxic sediment since pore water nitrate inhibited for about a month the respiration of metal oxides in the first cm of sediment, thus limiting PO₄ availability and the phytoplankton growth. In April and May (early spring), after exhaustion of pore water nitrate, the dissolutive reduction of iron oxides released PO₄ into pore water generated a significant diffusive outgoing flux from the sediment to the water column with a maximum in April (-1.10E-04±2.81E-05 nmol cm^-2 s^-1). This release coincided with the nanophytoplankton bloom (5.50 µg Chla L^-1) and a potential increase of PO₄ concentration in the water column. This work provides some insight on the importance of benthic-pelagic coupling in anthropogenic systems. This conceptual model has to be deployed on other sites of interest where internal loading of P takes precedence over external inputs and nitrate mitigation drives its benthic recycling and ultimately its bioavailability. This is to be essential to characterize the aquatic environment quality in order to limit eutrophication risks.

Keywords: Early diagenesis; Freshwater marsh; Iron; Nitrogen; Nutrient fluxes; Phosphorus; Phytoplankton.

MeSH terms

Eutrophication
France
Fresh Water
Geologic Sediments
Nitrogen / analysis
Phosphorus / analysis
Phytoplankton*
Wetlands*

Substances

Phosphorus
Nitrogen