Mapping the seabed of the Belgian part of the North Sea to assist in a science-based approach to management

Knowledge of the spatial distribution of sediments, the impact of human activities on the seabed and the natural evolution of the seabed is important to assist in a more sustainable management of the Belgian Part of the North Sea (BPNS). Sediments are an essential part of any aquatic system and are the key for a better understanding of the marine ecosystem; moreover, they are a valuable socio-economic resource for construction material and beach nourishment; therefore, they are extracted increasingly. Research on sediment nature and processes are important also for the optimisation of dredging and dumping activities, the implantation of windmill farms, seabed constructions, cables and pipelines, the designation of marine nature reserves and, generally, any spatial planning initiative.Related to the BPNS research, the Renard Centre of Marine Geology (RCMG) of Ghent University has been/is actively involved in various inter- and multidisciplinary projects. Throughout these projects, a research strategy is followed that balances between process/modelling studies, and the optimization of the use of various acoustical and sampling techniques.Results from three research projects, related to the mapping of the seabed of the BPNS, will be presented. During the Marebasse project (Belspo, SPSDII; http://users.ugent.be/~vvlancke/ Marebasse/), significant new sampling and acoustical data was acquired in typically mud-, sand- and gravel-dominated areas (Van Lancker et al., 2007). On the scale of the BPNS, new thematic maps, related to the bathymetry, sedimentology and morphology, were produced. Automated modelling of these physical data layers, based on advanced geostatistical methods, have resulted in physical habitat maps with ecological relevance. On a smaller scale, impact studies of aggregate extraction and dumping of dredged material were performed on selected sites, integrating results from geo-acoustical surveys and terrain verifications. Results have shown that, on a short- to medium-term, the effects seem relatively localised. All results are integrated into a Geographical Information System GIS@SEA (The physical seabed GIS to support Studies and Environmental Applications).As the Marebasse project focussed on the spatial variability of the seabed nature and the short- to medium-term impact of human activities, knowledge of the natural evolution of the seabed, its response to sea-level rise and the long-term anthropogenic impact remains poor. These issues are investigated now in the QUEST4D project (Belspo, SSD; http://www.vliz.be/projects/Quest4D/). Through quantification of erosion/sedimentation patterns, the natural evolution will be compared against the impact of human activities. Results will be presented of the area north of the Vlakte van de Raan, including the dumping ground Br&W S1. Acoustical maps of the seabed reveal different sedimentation and erosion patterns, originating from natural processes and human-induced activities (Van Lancker et al., 2008). The socio-economic importance of seabed resources is further dealt with in theRESOURCE-3D project (Belspo Targeted Action), in which a 3D reconstruction of the internal structure of sandbanks is aimed at. A case study on the Kwinte Bank will be presented

Translation of biological and sedimentological point data towards habitat suitability maps of biological communities and EUNIS level 5 maps. Part 2: From habitat suitability maps of biological communities towards EUNIS level 5 maps

The full coverage habitat suitability maps of the macrobenthic communities serve as an input to apply the EUNIS classification on the Belgian Continental Shelf and to translate the maps into EUNIS habitat types (EUNIS level 5 maps). The whole analysis was performed within a GIS (Geographic Information System). The habitat suitability maps were classified by means of the natural breaks classification scheme. Two derivative maps were generated, respectively exceeding probabilities of 60% and 70%. Subsequently, the derived habitat suitability maps were translated into EUNIS habitat types. A large proportion of the Belgian shelf is covered and assigned to EUNIS classes. Each defined EUNIS habitat type has a habitat suitability percentage exceeding 60%. So far, only the Macoma balthica community matches within the current EUNIS classification. The other communities do not exactly match classes within the EUNIS classification. As such, only temporary codes are created and those need an expert review. The Habitat model (Degraer et al., in prep.) does not foresee transitional communities; as such they cannot be mapped. Once these are defined, a complete full coverage EUNIS map can be attained

Acoustic habitat modelling for the mapping of biological communities

In the framework of the MAREBASSE project (‘‘Management, Research and Budgeting of Aggregates in Shelf Seas related to End-users’’, EV/02/18, Van Lancker et al. 2005) and the MESH project (“Mapping European Seabed Habitats, Interreg IIIb; www.searchmesh.net), biologically relevant habitat maps are produced, based on multibeam acoustic datasets, ground truthed with physical and biological samples. The habitat map production comprised of the following four key steps: (1) getting the best out of the ground truth data; (2) selecting and deriving the best available input and most appropriate data coverages; (3) using the most appropriate techniques for interpreting the data through integration and modelling, and; (4) designing the map layout to create a map fit for purpose. Results are presented where classes derived from acoustic seabed classification are translated into habitat maps. Cross tabulation is used to correlate biological ground truthing data with the acoustic classes. Finally, habitat maps are produced, representing the likely occurrences of the different macrobenthic communities occurring on the Belgian part of the North Sea (BPNS). For the study areas of Oostende, Hinder Banken, Sierra Ventana, habitat maps of macrobenthic communities have been created. The habitat maps are based on a cross tabulation of acoustic backscatter classification of the multibeam images, overlaid with biological samples worked out on a macrobenthic community level