Fouling fauna on offshore wind turbines and scour protection layers in the Belgian Part of the North Sea

Long term monitoring of the fauna colonising turbines and scour protection layers in Belgian offshore wind farms started in 2008. The monitoring focuses on monopile foundations from the Belwind offshore wind park, and on jacket and gravity based foundations from the C-Power park. During the first two years, the sampling occurred seasonally and across various depths of the selected foundations. Later, the samples were collected once a year in summer or autumn, at approximately 15 m depth on the foundations and from the scour protection layers. In BelWind, four monopile foundations were sampled through the monitoring period, but not simultaneously. In C-Power, the gravity-based turbine D5 was sampled through the entire duration of the monitoring, except in 2016 when samples were taken from D6. The jacket foundation (E1) from C-Power was sampled only once (one year after installation). The sample size was 0.0625 m2 and samples were deposited in a plastic bag. The scour protection layer stones were collected manually by divers. All samples were preserved in buffered 4% formalin. In the laboratory, the samples were extracted using a 1-mm sieve and were identified and where possible, all species counted. For most colonial species we accounted for presence only.