Benthic Communities at Horns Rev Before, During and After Con- struction of Horns Rev Offshore Wind Farm Final Report Annual Report 2005 Published: 31. May 2006 Prepared: Simon B. Leonhard Editing: Gitte Spanggaard John Pedersen Checked: Bjarne Moeslund Artwork: Kirsten Nygaard Approved: Simon B. Leonhard Cover photos: Jens Christensen Simon B. Leonhard Photos: Jens Christensen Maks Klaustrup Christian B. Hvidt Simon B. Leonhard English review: Matthew Cochran © No part of this publication may be reproduced by any means without clear reference to the source. Horns Rev. Benthic communities Page 3 Table of contents Page 1. Introduction.................................................................................................................16 1.1. Background .........................................................................................................16 1.2. Horns Rev...........................................................................................................17 1.2.1. Geology and geomorphology......................................................................18 1.2.2. Hydrography ...............................................................................................19 1.3. Horns Rev Offshore Wind Farm.........................................................................20 1.3.1. Construction and layout ..............................................................................20 1.3.2. Designated areas..........................................................................................22 1.4. Benthic communities at Horns Rev ....................................................................23 1.4.1. Benthic vegetation.......................................................................................23 1.4.2. Benthic fauna ..............................................................................................23 1.4.3. Population ecology and distribution at Horns Rev .....................................23 1.5. Scope of investigations .......................................................................................26 1.5.1. Possible and expected effects on benthic communities ..............................26 1.5.2. Criterion ......................................................................................................29 1.5.3. Hypotheses regarding effects ......................................................................30 2. Methods.......................................................................................................................31 2.1. Infauna.................................................................................................................31 2.1.1. Field surveys ...............................................................................................32 2.2. Hard bottom substrate .........................................................................................32 2.2.1. Field surveys ...............................................................................................33 2.3. Sample handling..................................................................................................35 2.3.1. Sediment......................................................................................................35 2.3.2. Benthos........................................................................................................35 2.4. Test fishing..........................................................................................................35 2.4.1. Objective .....................................................................................................36 2.5. Data analyses.......................................................................................................36 2.5.1. Sediment characteristics..............................................................................37 2.5.2. Species composition....................................................................................37 3. Results.........................................................................................................................40 3.1. Sediment..............................................................................................................40 3.2. Infauna.................................................................................................................42 3.2.1. Structure of the community.........................................................................47 3.3. Hard bottom substrate .........................................................................................50 3.3.1. Vegetation ...................................................................................................50 3.3.2. Epifauna ......................................................................................................52 3.3.3. Fish..............................................................................................................69 4. Discussion ...................................................................................................................71 4.1. Natural patterns in distribution and abundance...................................................71 4.2. Effects from the wind farm .................................................................................71 4.2.1. Construction ................................................................................................71 4.2.2. Operation.....................................................................................................80 4.2.3. Cumulative effects......................................................................................80 4.3. Methodological considerations for future studies (lessons learned)...................80 5. Conclusion ..................................................................................................................81 Doc. No. 2572-03-005 rev. 4 Horns Rev. Benthic communities Page 4 6. Acknowledgements.....................................................................................................83 7. References...................................................................................................................84 8. Appendixes..................................................................................................................90 8.1. Appendix 1. Coordinates of the wind farm and list of Positions ........................90 8.2. Appendix 2. Species Lists...................................................................................92 8.2.1. Appendix 2.1. Infauna 1999-2005 ..............................................................93 8.2.2. Appendix2.2. Algae ....................................................................................94 8.2.3. Appendix 2.3. Fish ......................................................................................94 8.2.4. Appendix 2.4. Hard bottom substrate. Benthos ..........................................95 8.3. Appendix 3. Infauna............................................................................................98 8.3.1. Appendix 3.1. Infauna mean abundance 1999-2004...................................98 8.3.2. Appendix 3.2. Infauna mean abundance 1999-2005 (spring).....................99 8.3.3. Appendix 3.3. Infauna mean biomass WW. 1999-2004 ...........................100 8.3.4. Appendix 3.4. Infauna mean biomass WW 1999-2005 (Spring)..............101 8.3.5. Appendix 3.4. Infauna mean biomass DW 1999-2005 (Spring)...............102 8.4. Appendix 4. Hard bottom substrate ..................................................................103 8.4.1. Appendix 4.1. Relative coverage. Monopiles ...........................................103 8.4.2. Appendix 4.3. Mean abundance. Monopiles 2003-2005 ..........................107 8.4.3. Appendix 4.4. Mean abundance. Scour protections 2003-2005 ...............113 8.4.4. Appendix 4.5. Mean biomass WW. Monopiles 2003-2005......................116 8.4.5. Appendix 4.6. Mean biomass WW. Scour protections 2003-2005...........122 8.4.6. Appendix 4.7. Mean biomass DW. Monopiles 2003-2005.......................125 8.4.7. Appendix 4.8. mean biomass DW. Scour protections 2003-2005 ............131 Doc. No. 2572-03-005 rev. 4 Horns Rev. Benthic communities Page 5 Summary In 1997, the Horns Rev area was designated as one of five areas suitable for future off- shore wind farm development pursuant to the Danish Action Plan for Offshore Wind Farms. In 2002, the Horns Rev Offshore Wind Farm was established with a production capacity of 160 MW. As part of the demonstration project, a monitoring programme was initiated to investigate the effects on the environment before, during and after the completion of the wind farm. The objective of the programme was to ensure that offshore wind power does not have damaging effects on natural ecosystems and to provide a solid basis for decisions for fur- ther offshore wind power development. The present study describes the effects on the ben- thic fauna and flora communities in the area designated for and later developed into the Horns Rev Offshore Wind Farm. Horns Rev – the site of location Horns Rev is an extension of Blåvands Huk, which extends more than 40 km to the west into the North Sea. The width of the reef varies between 1 km and 5 km and forms the northern extremity of the European Wadden Sea. Horns Rev was formed by sediment de- posited during earlier geological periods. Today these deposits are covered by huge ac- cumulations of marine sand and are subject