- This document reports on an investigation by divers into the marine colonisation of structures at the North Hoyle offshore wind farm, north Wales. The study took place between August 11th and 14th 2004 after the wind turbines had been in place for approximately 1 year and a meteorological mast for 3 months. In all cases the turbines were turning at the time of the visits, although not necessarily generating. At the time windspeeds were generally low and power generation was intermittent.
- Detailed descriptive information was obtained from two turbines and a recently installed meteorological mast using standard Phase 2 methodology. A further 4 turbines were surveyed briefly for comparison and to determine the zonation of communities. Digital underwater video was taken of all structures studied. A table of species identified together with abundances is presented.
- Although there was some variation between the turbines, a characteristic vertical zonation of communities was found to occur up and down these artificial structures. The dominant species included the barnacle Balanus crenatus, the amphipod Jassa falcata and the mussel Mytilus edulis. The common starfish Asterias rubens and the sea anemones Metridium senile, Sagartia elegans and Sagartia troglodytes were also conspicuous.
- A series of 0.01 m2 quadrats were scrapped clear of attached organisms in each zone (where practicable) on two turbines and the met mast. The samples were then weighed in order to obtain a rough estimate of biomass (wet weight). Based on the data obtained, it was calculated that the turbines would each have born around 1000 - 1300kg of attached marine life. The met mast having been in place for only six months bore just under 300 kg.
- Small invertebrate worms and crustaceans were picked out from the cleared quadrat samples and preserved for later laboratory determination. A list of the species obtained from the samples is enclosed with this report.
- The methodology together with the major findings of the survey is discussed. In summary, the species colonising the wind farm structure were all common species found on nearby hard substrata.
- Commercially fished species encountered during the survey included the whiting Merlangius merlangus and the edible crab Cancer pagurus as well as mussels. Very large shoals of juvenile whiting were observed around each of the underwater structures studied. At the base of turbine support no 30 a single specimen of the cod Gadus morhua was found swimming amongst the whiting, and the plaice Pleuronectes platessa was recorded at low abundance from the adjacent seabed, this record probably representing a single specimen. The significance of the wind farm to these species is unknown and warrants further investigation.
- Although the divers were aware of noise from the operation of the turbines, there was no obvious indiation that any of the fish were affected.