2013, Centre for Marine and Coastal Studies Ltd, Greater Gabbard Offshore Wind Farm, Year 1 Post-construction Benthic Ecology and Turbine Colonisation Survey

Description

Year one post-construction monitoring of marine benthic organisms and communities in and around the Greater Gabbard Offshore Wind Farm (GGOWF) and export cable route was undertaken in 2013 for comparison with data from a baseline survey completed in 2009 prior to commencement of construction, with further reference to data from 2005 and 2010 EIA surveys. Grab, trawl and drop-down camera surveys are reported here, while an ROV colonisation survey is reported separately.
In 2013, sediments within and around the GGOWF array areas generally consisted of gravelly sand along the sandbanks running parallel to the coastline and sandy gravel elsewhere. The majority were poorly sorted, particularly the coarser areas, which were mixed with a muddy element. Sediments were particularly muddy along inshore sections of the export cable route, generally becoming more coarse further offshore.
Infauna was largely dominated by polychaete worms, followed by crustaceans and molluscs. Echinoderms were less abundant and diverse, but important by weight. Epifauna was, however, hugely dominated by echinoderms, but from just a few taxa, while crustaceans were also reasonably numerous and were the most diverse and molluscs were reasonably diverse but in low numbers. Encrusting and turf species were also important. Communities occurring on more mixed gravelly sediments tended to be reasonably rich and diverse, while those along the sandbanks were comparatively depauperate. Fish were dominated by flatfish and gobies in muddier areas and by lesser weever fish, dragonet, hooknose and catsharks in more coarse areas. Statistical analysis demonstrated no significant differences in infaunal, epifaunal or fish communities between export cable route, near-field, wind farm and reference areas. Investigation with a camera recorded no significant aggregations of the reef-building Ross worm, nor any rocky reef. The benthic communites recorded in 2013 are generally similar to those historically found along this coastline.
The sediment types and distributions and faunal communities within and around the Greater Gabbard Offshore Wind Farm have generally remained reasonably similar throughout the survey programme thus far. While mud content decreased to a certain extent in 2013 compared to 2009, with some apparent effects upon faunal composition, levels were demonstrated as having returned to those recorded in 2005. When considered alongside fluctuations observed at reference stations, it seems natural variability most likely arising from storm events are attributable, rather than any effects of the construction and operation of the wind farm.