A. Norro

Epifaunal inventory of two shipwrecks from the Belgian Continental Shelf

Shipwrecks are almost the only subtidal substrata available for epifaunal colonization along the Belgian coastal waters and have never been scientifically prospected up to now. Two shipwrecks have been investigated during the summers of 2001 and 2002. De-visu observations and examination of 14 scraped surfaces of 0.0625 m2 allowed the identification of a total of 121 macrofauna species. Species richness cumulative curves provide an estimated number of 150–280 species. Both shipwrecks are dominated by Cnidarians. The tube-dwelling amphipod Jassa herdmani was also particularly abundant. Striking differences were observed between shipwrecks. Different faunal assemblages were observed on vertical and horizontal surfaces. Species richness could not been correlated with diversity indices. Samples with high species diversity were observed when the Hydrozoan Tubularia indivisa was dominant. On the contrary, when the Anthozoan Metridium senile was dominant, samples showed a very low species richness. Finally, the Poriferan Dysidea fragilis has to be considered as a new species for the Belgian fauna.

Differentiating between Underwater Construction Noise of Monopile and Jacket Foundations for Offshore Windmills: A Case Study from the Belgian Part of the North Sea

Steel monopiles, jackets requiring four steel pinpiles, and gravity-based foundations were applied in offshore wind farms in the Belgian part of the North Sea. This paper compares the underwater noise generated during the piling activities of steel monopiles at the Belwind wind farm (Blighbank) with that of jacket pinpiles at the C-Power project (Thorntonbank). Underwater noise was measured at various distances from the pile driving location. The underwater noise was quantified by its zero to peak sound pressure level (L z−p), unweighted sound exposure level (SEL), cumulative SEL, and 1/3 octave spectra. No significant differences in L z−p could be demonstrated (monopile L z−p: 179–194 dB re 1 μPa, jacket L z−p: 172–189 dB re 1 μPa). SEL showed no statistical difference between monopile and jacket and varied between 145 and 168 dB re 1 μPa2s. Furthermore, near identical spectra were measured for both types of piling. Piling of the jacket pinpiles took, however, about 2.5 times the time of the monopile. When standardised to megawatt installed per foundation both types of piling scored near equally. As an illustration, the radius of major behavioural disturbance (L p−p = 155 dB re 1 μPa) in the harbour porpoise Phocoena phocoena was estimated by a model at 16 km for monopiles and at 8 km for jacket.