Benthic habitat tool: to evaluate management and climate scenarios in the Sea Scheldt estuary

With the expected increase of hydrological pressure caused by sea level rise, the Scheldt estuary is expected to face morphological river modifications that can reduce or amplify expected ecological responses to climate change. Therefore a predictive tool for benthic habitat assessment is developed, allowing inclusion of hydrodynamics as a potentially important driver of benthic community composition and density.
In order to develop such a tool, a sampling campaign and ecological modelling approach were set up to characterise the habitat of the benthic species and communities in subtidal habitats of the freshwater and brackish part of the Scheldt. Along with the benthic communities, data on flow velocities, soil morphology type, water depth, sediment characteristics and organic matter content were collected.
Multiple regression analyses revealed distinct subtidal benthic communities in shallower areas with low flood velocity and deeper areas with higher flood velocities.
A new habitat typology is derived by threshold analysis of the most relevant variables in relation to macrobenthic density. The robustness of the typology is tested on independent macrobenthic long- term monitoring data (the Belgian-Dutch framework of MONEOS). Compared to the previously used ecological typology, water velocity is included to monitor and predict the evolution of subtidal habitats and species in the Sea Scheldt estuary (Belgian part of the Scheldt estuary). This has resulted in an improved, ecologically validated instrument for impact assessment of climate change in 2050 and management measures and infrastructure works, such as sediment dumping or river cut-offs. As such, abiotic data can allow defining mitigation measures to minimise the ecological impact of these measures.