Lessons learned from the benthic monitoring evaluation in alpha ventus
Numerous ecosystem goods and services, such as marine biodiversity, long-term carbon storage and natural resources (e.g. for fish, birds, mammals and finally humans), are intimately linked to the benthic system. Maintenance of the benthic system at a healthy ecological status is thus of particular interest. The mandatory monitoring concept of offshore wind farm effects on the marine environment (StUK) prescribes extensive investigations on soft-bottom benthos and fouling assemblages of the wind turbine foundations. StUK and studies beyond StUK in the test field alpha ventus (North Sea, German Bight) were carried out to evaluate the German monitoring concept. Our investigations show a massive colonization of turbine foundations by fouling organisms and an aggregation of megafauna around constructions, both resulting in a local increase in biomass and species richness of the benthos, but no direct turbine effects on the soft-bottom benthos at the scale investigated. Temporal variations of sediment conditions and benthic communities were similar inside and outside the wind farm area. During the alpha ventus case-study, limits of benthic ecological studies according to StUK became evident and recommendations were elaborated for future improvements. Beyond our field studies, an aggregated database of StUK data from approved wind farms and data from research projects serves as the base for large-scale benthic ecosystem analysis. Current efforts are being made to quantitatively estimate benthic species distributions on a transnational scale, a prerequisite for cross-border spatial planning. Further, we strive to estimate species or group specific “natural corridors of variation” to discriminate anthropogenic effects from natural background variability. Finally, functionally sensible areas and important geographic sites that are of public concern regarding ecosystem services and goods are to be identified. This data will be used to provide evaluation criteria for identifying sensible areas in the context of licensing procedures of offshore wind farms and marine spatial planning. Study outcomes (e.g. in terms of maps) are made public via the internet (GeoSeaPortal) in order to provide stakeholders, e.g. authorities and scientific institutions, with scientific advice.