title: A doubling of microphytobenthos biomass coincides with a tenfold increase in denitrifier and total bacterial abundances in intertidal sediments of a temperate estuary.
abstract: Surface sediments are important systems for the removal of anthropogenically derived inorganic nitrogen in estuaries. They are often characterized by the presence of a microphytobenthos (MPB) biofilm, which can impact bacterial communities in underlying sediments for example by secretion of extracellular polymeric substances (EPS) and competition for nutrients (including nitrogen). Pyrosequencing and qPCR was performed on two intertidal surface sediments of the Westerschelde estuary characterized by a two-fold difference in MPB biomass but no difference in MPB composition. Doubling of MPB biomass was accompanied by a disproportionately (ten-fold) increase in total bacterial abundances while, unexpectedly, no difference in general community structure was observed, despite significantly lower bacterial richness and distinct community membership, mostly for non-abundant taxa. Denitrifier abundances corresponded likewise while community structure, both for nirS and nirK denitrifiers, remained unchanged, suggesting that competition with diatoms for nitrate is negligible at concentrations in the investigated sediments (appr. 1 mg/l NO3-). This study indicates that MPB biomass increase has a general, significantly positive effect on total bacterial and denitrifier abundances, with stimulation or inhibition of specific bacterial groups that however do not result in a re-structured community.
authors.affiliation: Laboratory of Microbiology (LM-UGent), Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium.
authors.forename: Helen
authors.initials: H
authors.lastname: Decleyre
authors.affiliation: Laboratory of Microbiology (LM-UGent), Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium.
authors.forename: Kim
authors.initials: K
authors.lastname: Heylen
authors.affiliation: Laboratory of Protistology and Aquatic Ecology, Department of Biology, Ghent University, Ghent, Belgium.
authors.forename: Koen
authors.initials: K
authors.lastname: Sabbe
authors.affiliation: Laboratory of Microbiology (LM-UGent), Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium.
authors.forename: Bjorn
authors.initials: B
authors.lastname: Tytgat
authors.affiliation: Laboratory of Pharmaceutical Biotechnology, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
authors.forename: Dieter
authors.initials: D
authors.lastname: Deforce
authors.affiliation: Laboratory of Pharmaceutical Biotechnology, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
authors.forename: Filip
authors.initials: F
authors.lastname: Van Nieuwerburgh
authors.affiliation: Marine Biology Research Group, Department of Biology, Ghent University, Ghent, Belgium.
authors.forename: Carl
authors.initials: C
authors.lastname: Van Colen
authors.affiliation: Laboratory of Microbiology (LM-UGent), Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium.
authors.forename: Anne
authors.initials: A
authors.lastname: Willems
mesh_terms: D018533:Biomass; D017753:Ecosystem; D063366:Estuaries; D019015:Geologic Sediments / Q000032:analysis*