Epifauna dynamics at an offshore foundation e Implications of future wind power farming in the North Sea Roland Krone a, * , Lars Gutow a , Tanja J. Joschko b , Alexander Schröder c a Department of Functional Ecology, Alfred Wegener Institute for Polarand Marine Research, AWI, Am Handelshafen 12, 27570 Bremerhaven, Germany b University of Koblenz-Landau, Fortstrasse 7, 76829 Landau, Germany c Department of River Basin Management, Transitional and Coastal Waters, NLWKN Lower Saxony Water Management Agency, NLWKN, Ratsherr-Schulze-Str.10, 26122 Oldenburg, Germany article info Article history: Received 23 May 2012 Received in revised form 11 December 2012 Accepted 12 December 2012 Keywords: Offshore structures German Bight Habitat creation Artificial habitats Biofouling Benthic ecology ‘Mytilusation’ Environmental impact abstract In the light of the introduction of thousands of large offshore wind power foundations into the North Sea within the next decades, this manuscript focuses on the biofouling processes and likely reef effects. The study explores the macrozoobenthos (biofouling) colonization at an offshore platform which is comparable to offshore wind turbine foundations. A total of 183 single samples were taken and the parameters water depth and time were considered comparing biofouling masses and communities. The blue mussel Mytilus edulis, Anthozoa and the Amphipoda Jassa spp. were the dominant species. The community from the 1 m zone and those from the 5 and 20e28 m zones can clearly be differentiated. The 10 m zone community represents the transition between the M. edulis dominated 1 m and 5 m zones and the Anthozoa dominated 20e28 m zone. In the future offshore wind farms, thousands of wind turbine foundations will provide habitat for a hard bottom fauna which is otherwise restricted to the sparse rocky habitats scattered within extensive sedimentary soft bottoms of the German Bight. However, offshore wind power foundations cannot be considered natural rock equivalents as they selectively increase certain natural hard bottom species. The surface of the construction (1280 m 2 ) was covered by an average of 4300 kg biomass. This foundation concentrates on its footprint area (1024 m 2 ) 35 times more macrozoobenthos biomass than the same area of soft bottom in the German exclusive economic zone (0.12 kg m 2 ), functioning as a biomass hotspot. Concerning the temporal biomass variation, we assume that at least 2700 kg biomass was exported on a yearly basis. 345  10 4 single mussel shells of different sizes were produced during the study period. It is anticipated that the M. edulis abundance will increase in the North Sea due to the expansion of the offshore wind farm development. This will result in the enhanced production of secondary hard substrate (mussel shells) and its associated fauna and will intensify filtration rates of the seawater. This predicted ecological system change is coined the ’Mytilusation’ of the German Bight. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction In the near future the wind energy industry will expand on a large scale into offshore regions of western European shelf seas. Thousands of large steel turbine foundations will function as artificial reefs within areas which are naturally characterised by extensive sedimentary soft bottoms. It is expected that the turbine foundations will affect marine life through noise emission (Wahlberg and Westerberg, 2005; Madsen et al., 2006; Lindeboom et al., 2011), changed seafloor topography and sedi- ment regimes (Wilson et al., 2010), and barrier effects (Masden et al., 2009). Additionally, strong implications for the subtidal ecosystem are expected from the settlement of macrozoobenthos on the artificial solid surface of the turbine foundations (Lindeboom et al., 2011). The macrozoobenthos communities on artificial hard substrata (biofouling or fouling) differ from natural macrozoobenthos communities on natural hard substrata (People, 2006; Wilhelmsson and Malm; 2008; Andersson et al., 2010) and on soft bottoms (Barros et al., 2001 Fabi et al., 2002; Langlois et al., 2006; Langhamer, 2010). In particular, in areas were natural hard substrata are rare, high numbers of artificial constructions favour the establishment of taxa such as cnidarians and mussels whose life histories include temporary or permanent * Corresponding author. Tel.: þ49 0 471 4831 1705; fax: þ49 0 471 4831 2142. E-mail addresses: mail@krone-meereskunde.de, Roland.krone@awi.de (R. Krone), Lars.Gutow@awi.de (L. Gutow), joschko@uni-landau.de (T.J. Joschko), Alexander.Schroeder@NLWKN-OL.Niedersachsen.de (A. Schröder). Contents lists available at SciVerse ScienceDirect Marine Environmental Research journal homepage: www.elsevier.com/locate/marenvrev 0141-1136/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.marenvres.2012.12.004 Marine Environmental Research 85 (2013) 1e12