Abstract
The introduction of artificial hard substrates in an area dominated by a sandy seabed increases habitat available to epifouling organisms. To investigate this, samples were taken on old offshore oil and gas platforms, and data were compared with data of a young wind farm and a natural reef. Depth, sampling date, abundance of Mytilus edulis, Psammechinus miliaris, Metridium dianthus, and the presence of Tubulariidae and substrate (rock or steel) all correlated with species richness. Multivariate analysis showed a large overlap in communities on steel and rock and between the wind farm and platforms. The community changed over a gradient from deep rocks to shallow steel substrate, but no strong community differentiation was observed. Deep steel was more similar to natural rocks than shallow steel. When an artificial reef is intended to be colonized by communities similar to those on a natural reef, its structure should resemble a natural reef as much as possible.