Offshore wind farm artificial reefs affect ecosystem structure and functioning: a synthesis

Offshore wind farms (OWFs) are proliferating globally. The submerged parts of their structures act as artificial reefs, providing new habitats and likely affecting fisheries resources. While acknowledging that the footprints of these structures may result in loss of habitat, usually soft sediment, we focus on how the artificial reefs established by OWFs affect ecosystem structure and functioning. Structurally, the ecological response begins with high diversity and biomass in the flora and fauna that gradually colonize the complex hard substrate habitat. The species may include nonindigenous ones that are extending their spatial distributions and/or strengthening populations, locally rare species (e.g., hard substrate-associated fish), and habitat-forming species that further increase habitat complexity. Functionally, the response begins with dominant suspension feeders that filter organic matter from the water column. Their fecal deposits alter the surrounding seafloor communities by locally increasing food availability, and higher trophic levels (fish, birds, marine mammals) also profit from locally increased food availability and/or shelter. The structural and functional effects extend in space and time, impacting species differently throughout their life cycles. Effects must be assessed at those larger spatiotemporal scales.