Water turbidity is caused by suspended particulate matter (SPM) and/or dissolved matter. Turbidity is related to light availability and controls primary production, while SPM concentrations are directly associated with benthic habitats, biodiversity, sediment transport and hence the fate of pollutant. In coastal waters, SPM occurs as flocs of highly variable sizes, which can settle to the sea floor. Flocculation combines biomass and sediments together into larger aggregates and has critical impact on sediment transport in marine and estuarine environments through the modification of settling velocities. SPM mediates many hydrodynamics and bio-physico-chemical processes that are of particular interest in relation to ecosystem functions, eutrophication and to the fate and burial of pollutants. As a consequence of the high SPM variability, both in time and space, measuring turbidity and SPM mass concentration is a challenging issue, mainly because all state of the art methods are based on indirect measurements. This project aims to:
i) observe and understand mechanisms controlling the SPM dynamics in coastal waters, and particularly focusing on the bio-sediment interactions
ii) update flocculation concepts including the role of biological material
iii) Evaluate and improve SPM measurement methodologies, in relation with SPM variability, and estimate their uncertainties.
This PhD position will be co-supervised between Ifremer and RBINS, and will consist in i) analysing a unique 10-year discontinuous time series of hydrodynamics, physico-chemical and SPM features; ii) collecting new measurements (SPM composition, size and organic matter content) dedicated to the understanding of bio-sediment interactions, both in the Seine Bay and the Belgian Shelf.