Benthic-pelagic coupling in a changing estuary

Master Thesis subject (30 ECTS)
Estuaries and shallow coastal habitats are ranked among the most productive marine ecosystems, and provide essential ecosystem services such as the filtering of pollutants and nutrient recycling. In addition to nutrient supply from land run-off and from the atmosphere, the internal recycling of nutrients within these systems substantially contributes to their nutrient load. This recycling largely results from remineralization of organic matter in sediments and the subsequent release of (part of these) nutrients to the water column (i.e. benthic-pelagic coupling). These nutrients support primary production that, together with imported organic matter, is at the basis of the pelagic and benthic foodwebs. A high benthic faunal biomass is a prominent feature of many healthy estuaries. It forms an important food source for many birds, fish and mammals. Larger sediment animals (macrobenthos), like worms, shellfish and crustaceans, also play important roles in benthic-pelagic coupling. For example, suspension feeders capture suspended organic matter from the water column (SPM) and incorporate part of it in the sediment. Furthermore, many macrobenthic species mediate benthic-pelagic coupling through bio-irrigation and bioturbation activities. Sediment mixing activities, for instance, enhance the reoxidation of reduced substances and facilitate removal of fixed nitrogen, thereby counteracting eutrophication. Nevertheless, current coastal zone and estuarine water quality models do not include formulations for macrobenthos-mediated benthic-pelagic coupling and are therefore not capable of projecting the impact of on ecosystem functioning due to change in morphology and hydrodynamics related to dredging activities and sea level rise. The aim of this thesis research is to gain insight into spatio-temporal variability of benthic-pelagic coupling in the Schelde estuary, in particular the role of macrobenthos. Therefore you will quantify benthic-pelagic fluxes for all the major sediment habitats along the whole estuarine gradient. This will allow for the first time to investigate the relative importance of different habitat types and macrobenthos on the exchange of dissolved nutrients between the sediment and water column on the scale of a whole estuary. This will enhance the prediction of the potential impact of hydro-morphological changes on estuarine ecosystem functioning and water quality.
Number of students: 
academic year: 
Reference Number: RP-36222