Offshore wind farm benthic functioning

Jennifer.Dannheim [ at ]


The construction of offshore wind farms (OWF) introduces artificial hard substrate to marine ecosystems, providing a valuable habitat for the establishment of fouling communities. The North Sea is mainly dominated by soft-bottom sediments and natural hard-bottom substrates are rare. Whereas community structures on these introduced structures are well known in terms of taxonomic composition and abundance, knowledge on possible effects on the functionality is scarce. It is therefore unknown if the hard-bottom communities have different functions than the soft-bottom communities and if the establishing of the former leads to a change in functionality of the latter. Therefore both, hard-bottom and soft-bottom data from the OWF alpha ventus and a soft-bottom reference area were sampled from 2008 to 2012 to compare functional differences. For the underlying taxonomic datasets, functional modalities were assigned to each species and examined with a biological trait analysis (BTA). The functionality of hard-bottom communities clearly differed from those of the two soft-bottom communities, but only in the first three years of the study period. In 2012 a convergence of the fouling and the soft-bottom communities could be seen, probably indicating a biological homogenisation. In addition, the introduction of the artificial hard substrate and the subsequent succession of fouling communities seemed to have no effect on the functions of the nearby soft-bottom communities. All communities were subject to slight fluctuations in the occurrence of respective trait modalities, which was probably caused by natural variability. As this study was limited in terms of time and space, only assumptions about the actual differences in functionality can be made. For clear statements the communities on the hard-bottom substrate should be investigated after reaching a more mature or even climax state, also more than one OWF and its surrounding soft-bottom would need to be investigated. Habitat-specific trait modalities for each species are expected to increase discriminatory power in this context. This would help us to understand and evaluate the influence of the forthcoming large-scale introduction of OWFs into marine ecosystems.

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Thesis (Bachelor)
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Gebhardt, A. (2016): Offshore wind farm benthic functioning , Bachelor thesis, Universität Bremen, Alfred-Wegener-Institut, Helmholtz Zentrum für Polar- und Meeresforschung.

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