Shifts in Microbial Communities and Nutrient Fluxes Induced by Offshore Wind Farm Development in the North Sea

• Applicant: Dr. Chandni Sidhu, Ph.D.
• Subject Area: Oceanography
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 569718716

Offshore wind energy plays an increasingly vital role in the sustainable blue economy on a global scale. For Germany, which has set the target of achieving greenhouse gas neutrality by 2045, offshore wind energy production is of particular importance. The planning and development of large-scale Offshore Wind Farms (OWFs) within Germany’s Exclusive Economic Zone in the North and Baltic Seas have raised concerns about potential effects on the marine environment, necessitating thorough scientific evaluations. Existing impact assessments have primarily focused on higher animals, such as demersal fish, birds, and marine mammals. However, there is a significant gap in understanding the potential impacts on marine plankton, specifically bacteria, phyto-, and zooplankton, which are essential to the functioning of highly productive coastal ecosystems. The North Sea ecosystem is globally important due to its high phytoplankton primary production, which forms the foundation of a complex marine food web. The impact of OWFs on primary production may be multifaceted. The wake effect of OWF turbines can increase water column mixing, bringing benthic nutrients to the surface and promoting phytoplankton growth. Conversely, increased turbidity from resuspended sediment and enhanced grazing by filter feeders colonizing the submerged turbine basal structures may impair phytoplankton productivity. Large-scale OWFs may also impact the bottom shear stress patterns and nutrient distribution. These combined effects could influence the composition, activity, and interactions of plankton communities within the microbial loop, a crucial component of the pelagic North Sea ecosystem. The proposed study aims to address the following key gaps: • Investigate whether marine plankton communities in the Meerwind OWF differ significantly from those at the selected reference sites, and how these differences vary both spatially and temporally. • Assess whether the presence of OWF foundations lead to a net increase or decline in primary productivity, based on observational data. • Examine how changes in primary productivity affect the production of dissolved and particulate organic matter, including dissolved organic carbon and dissolved organic nitrogen. To the best of our knowledge, no fine-scale spatial research has been conducted that specifically examines the potential impact of OWFs on lower trophic levels using real in situ seawater samples. Besides the aforementioned key questions, this research project also aims to: - Analyze plankton composition and identify early indicators of ecosystem stress at OWF sites. - Investigate potential changes in plankton communities in relation to the biogeochemical cycling of carbon, sulfur, and nitrogen. - Establish a link between microbial indicators and the functional activity of the North Sea ecosystem. - Develop predictive models to assess the ecological impacts of OWFs and enable early detection of environmental shifts.

• DFG Programme: Research Grants