|Structural and functional biological assessment of aggregate dredging intensity on the Belgian part of the North Sea|
De Backer, A.; Hillewaert, H.; Van Hoey, G.; Wittoeck, J.; Hostens, K. (2014). Structural and functional biological assessment of aggregate dredging intensity on the Belgian part of the North Sea, in: De Mol, L. et al. (Ed.) 'Which future for the sand extraction in the Belgian part of the North Sea?'. Study day, 20 October 2014, Belgium Pier - Blankenberge. pp. 29-58
In: De Mol, L.; Vandenreyken, H. (Ed.) (2014). 'Which future for the sand extraction in the Belgian part of the North Sea?'. Study day, 20 October 2014, Belgium Pier - Blankenberge. FPS Economy, Continental Shelf Service: Brussel. 117 pp., more
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Marine aggregate dredging in the Belgian part of the North Sea (BPNS) is restricted to four dedicated concession zones. Within these zones, there are areas under different dredging pressure, but with the advantage that these are situated within a similar habitat (cfr. similar sediment characteristics) . As such, this study assessed how different degrees of dredging pressure executed on a similar sandy habitat affect the benthic ecosystem. Possible responses of the macrobenthos on the dredging pressure were evaluated based on both structural (species number, species composition, abundance and biomass) and functional (e.g. bioturbation potential, BTA) characteristics of the benthic ecosystem. The structural changes in benthic characteristics were summarised by the benthic indicator BEQI.The most obvious impact of dredging on the benthic community was observed in the most intensely used area (high dredging intensity and frequency) with significant changes in the structural benthic characteristics, and a moderate to poor score for the benthic indicator BEQI. For the benthic functional characteristics, no impact of dredging was measured in any of the areas. Furthermore, the hearturchin (Echinocardium cordatum) was observed to be the most sensitive species to dredging, because it reduced substantially in numbers or even disappeared in all impacted areas.Our results suggest that the current benthic sandy ecosystem of the BPNS is resilient enough to buffer aggregate dredging when performed at low or at high, but infrequent intensities. However, when dredging focuses on a small surface area, and when it is performed at high and frequent intensities, changes in sediments result in clear biological changes.