Engineering Hard Bottom Substrate Monitoring Horns Rev Offshore Wind Farm Annual Status Report 2004 v 'TW- ELsam Engineering Hard Bottom Substrate Monitoring Horns Rev Offshore Wind Farm Annual Status Report 2004 Published: 2. May 2005 Prepared: Simon B. Leonhard Editing: Gitte Spanggaard John Pedersen Checked: Bjame Moeslund Artwork: Kirsten Nygaard Approved: Simon B. Leonhard Cover photos: Jens Christensen Simon B. Leonhard Photos: Jens Christensen Maks Klaustmp Simon B. Leonhard English review: Matthew Cochran © No part of this publication may be reproduced by any means without clear reference to the source. Homs Rev. Hard Bottom Substrate Monitoring Page 3 Annual Status Report 2004 TABLE OF CONTENTS PAGE Summary.................................................................................................................................... 4 Sammenfatning (in Danish) ....................................................................................................... 7 1. Introduction ......................................................................................................................... 10 2. Methodology....................................................................................................................... 11 2.1. The research area...........................................................................................................11 2.2. Field activities................................................................................................................13 2.3. Test fishing................................................................................................................... 14 2.4. Laboratory activities.................................................................................................... 15 2.5. Statistical analyses.........................................................................................................15 2.5.1. Species composition.............................................................................................. 15 3. Results ...................................................................................................................................17 3.1. Fish observed .................................................................................................................17 3.2. Additional field observations .........................................................................................18 3.3. Vegetation......................................................................................................................18 3.4. Fauna ............................................................................................................................. 20 3.4.1. Mono-piles ............................................................................................................. 24 3.4.2. Scour protection ..................................................................................................... 31 3.5. Comparisons with results from 2003............................................................................ 36 3.5.1. Fish......................................................................................................................... 36 3.5.2. Vegetation.............................................................................................................. 37 3.5.3. Fauna ...................................................................................................................... 39 4. Discussion ............................................................................................................................ 45 5. Conclusion ........................................................................................................................... 50 6. References ............................................................................................................................ 52 Appendixes .............................................................................................................................. 55 Appendix 1. List of Positions ............................................................................................... 55 Appendix 2. Meteorological and Hydrographical Data....................................................... 56 Appendix 3. Species List..................................................................................................... 57 Appendix 3.1. Algae........................................................................................................ 57 Appendix 3.2. Fish........................................................................................................... 57 Appendix 3.3. Benthos ..................................................................................................... 58 Appendix 4. Sampling records. Fish species observed .........................................................60 Appendix 5. Transect description ........................................................................................ 62 Appendix 5.1. Transect description. Scour protection ..................................................... 62 Appendix 5.2. Transect description. Mono-piles ............................................................. 64 Appendix 6. Benthic Fauna abundance................................................................................ 66 Appendix 6.1. Total abundance........................................................................................ 66 Appendix 6.2. Mean abundance mono-piles.................................................................... 68 Appendix 6.3. Mean abundance scour protection ............................................................ 71 Appendix 7. Biomass........................................................................................................... 73 Appendix 7.1. Total biomass........................................................................................... 73 Appendix 7.2. Mean biomass. Mono-piles ...................................................................... 75 Appendix 7.3. Mean biomass. Scour protections ............................................................ 78 Doc. No. 2438-03-005 rev. 3 Homs Rev. Hard Bottom Substrate Monitoring Page 4 Annual Status Report 2004 Summary As part of the monitoring programme concerning the ecological impact from the introduction of hard substrate related to the Horns Rev Wind Farm, the second survey on the fouling communities since the erection of the wind farm in 2002 was performed in March and Sep­ tember 2004. The survey is a continuation of the survey performed in 2003. Horns Rev is situated 14-20 km off Blavands Huk, Denmark ’s most western point. Horns Rev was formed by a huge accumulation of Holocene marine sand deposits up to 20 m in depth. The water depth in the wind farm area varies from 6-14 m. The first of a total of 80 wind tur ­ bine foundations was in place in March 2003 and the last of the foundations was in place in August 2003. Methodology The wind turbine (WTG) foundations are constructed using the “mono-pile ” concept. At the seabed, a "gravel mattress" or scour protection is arranged around the foundation to minimise erosion. The diameter of the mono-pile foundation of the turbines is 4 m. The scour protection with a diameter of approximately 27 m in total consists of a protective stone mattress of stones up to 55 cm in diameter and a subjacent layer of smaller stones 3-20 cm in diameter. Surveys were performed at six turbine sites concerning the horizontal distribution of epifoul- ing assemblages on scour protections whereas the vertical distribution of epifouling assem­ blages was only performed at tree mono-piles. Epifouling communities exposed to different current regimes were studied both on the mono-piles as well as on the scour protection. Sampling was performed by SCUBA diving. Quantitative samples were collected from stone blocks and mono-piles while semi-quantitative (not precisely counted records) observations on flora- and fauna fouling communities were made according to a modified Braun-Blanquet scale along transects on both the scour protections and the mono-piles. Fish species were ob­ served and in addition standard gill nets were used for specific test fishing. For documenta­ tion, under water video recordings were made. In March, samples were taken on populations of the “giant” midge Telmatogeton japonicus inhabiting the splash/wash zone at the mono-piles. Recent observations on Telmatogeton japonicus, recorded for the first time in Denmark at Horns Rev in 2003, have revealed that this species is common and widely distributed on strongly exposed coasts in Denmark. It is especially common on large boulders in breakwaters and seawalls. Results flora A total of 11 taxa of seaweeds were registered on the mono-piles and scour protections showing a distinct variation in spatial and temporal distribution. The vegetation was more fre­ quently found on the mono-piles compared to the scour protections. Only a few species were found on stones at the scour protections and almost exclusively at turbine sites in the shallow­ est areas. Typical vertical zonations were found on the mono-piles with the species of Ulva (Enteromorpha) being the most frequent. Considerable changes in the vegetation community especially in the splash zone and at the upper part of the mono-piles between 2003 and 2004 were observed which might be a result of natural succession. The vegetation cover of fila­ mentous algae was more