Influence of sediment on the chemical properties of water in coastal environment and their potential effect on heterotrophic prokaryotic growth

This work aims to carry out a field diagnosis of the sedimentary column influence on the spatial variability of the surface waters chemical composition in an urbanized bay. The spatial distributions of nutrients, dissolved organic matter, and radium isotopes used as sediment tracers were determined. Additionally, laboratory incubations were performed to evaluate the influence of the sedimentary column on the growth of heterotrophic prokaryotes (HP). To do so, a natural HP community was exposed to dissolved substances collected from the bay. First, radium concentrations were positively correlated with concentrations of some fluorescent compounds in the dissolved organic matter, dissolved inorganic phosphorus and dissolved organic nitrogen, suggesting that sediment inputs caused chemical alterations. Second, HP growth was strongly stimulated by dissolved substances derived from sediments, identified by correlation with radium, leading to an abundance up to 34 times that of the maximum observable with dissolved substances without recent influence from sediments.