Estuarine biodiversity and ecosystem functioning under benthic and pelagic sediment change

Progress not set: October 2014 -

In the Schelde estuary, it is yet unknown how resilient macrobenthic populations are to sediment change. This PhD project studies relationships between biodiversity and ecosystem functioning and their responses to changes in sediment properties. Benthic-pelagic fluxes of solutes for the major benthic habitats will be quantified along the estuarine gradient. Nutrient exchange, organic matter remineralization, bio-irrigation and bioturbation will be measured in different benthic communities and periods of the year. The governing mechanisms of benthic-pelagic coupling should depend on the environmental context, and thus vary along both the spatial gradients in salinity, grain size and depth; and the seasonal changes in sediment and water column properties.
In addition, the influence of suspended sediments on macrobenthos-mediated biogeochemical cycling will be investigated by documenting species behaviour under experimental conditions. This will be done by using bio-irrigation and luminophore reworking rates in mesocosm experiments that contain communities from the different benthic habitats along the estuary. Experimental variation in suspended sediment concentrations is hypothesized to alter benthos-mediated change in benthic-pelagic coupling through changes in benthos condition and behaviour. Resilience to sediment change will also be tested in a deposition experiment. Because added deposits will change the sediment surface cohesiveness and nutritional characteristics, and ability of the macrobenthos to maintain contact with the sediment-water interface, we hypothesize that deposition events will inhibit transport of material and solutes across the sediment-water interface, altering benthic-pelagic coupling.
Eventually, insights into benthic-pelagic coupling obtained from measurements along the estuary and from experiments will be integrated to understand the consequences of benthic and pelagic sediment change for estuarine biodiversity and ecosystem functioning.