4 minute read
Wind Farm Oyster Reefs
Borssele, Zeeland, the Netherlands
Analyzing oyster growth in an offshore environment. The European flat oyster (Ostrea edulis) used to cover about 20% of the Dutch part of the North Sea; but overharvesting, habitat destruction from bottom-trawling fisheries, and disease drove the species nearly to extinction. As bottom-trawling activities are not allowed at wind farms to protect subsea cables, the innovation wind farm Borssele V, located 20 kilometers off the coast of the Netherlands in the North Sea, provided an excellent setting for an oyster reef rehabilitation project. In 2018, the research team, led by Van Oord DMC, began by analyzing the settlement rates of oyster spat on different types of substrate. They then identified the potential logistical obstacles in obtaining the required number of oysters to stock the area, and finally they developed their own brood stock structure to induce reef development via natural spawning and larvae settlement in the offshore wind farm. By designing effective methods for initiating sustainable oyster reefs at the rock material scour protection placed around the base of each offshore wind turbine, the team has added yet another benefit to renewable energy.
Article cover: Installing the scour protection at the base of each wind turbine. (Photo by Van Oord)
Producing Efficiencies
The main purpose of the Borssele V wind farm is to test technical innovations at real scale. Therefore, the knowledge gained of the various procedures, materials, and conditions that encourage oyster reef development will more easily translate to other offshore wind farms. This eliminates the need for further follow-up studies in the laboratory or at other turbines to ensure broad applicability. The most effective substrates and supply chains at Borssele V will also be effective at other offshore wind farms, allowing large-scale deployment of oyster reefs for scour protection and ecosystem recovery.
Using Natural Processes
The wind farm provides a place, undisturbed by trawling, for oyster establishment, growth, and recovery. Determining the most effective life stage, placement method, and substrate to kick-start reef development now allows the oyster reef to be induced, grow, and become self-sustaining. And as the oysters cover the base of the monopiles, they naturally protect the turbines of the wind farm from the scouring that occurs as sediment moving in the current scrapes past the surface of the monopiles. Eventually the oysters may also form a reef between the turbines, stabilizing the sandy seabed.
Broadening Benefits
Offshore wind farms reduce a country’s dependence on fossil fuels and reduce their resulting pollutants, benefiting all sectors of society. In the Netherlands, there is an additional regulatory as well as an ethical duty to ensure the designs also include nature-friendly elements. A new wind farm provides an opportunity to benefit the local habitat, aiding the conservation of endangered and threatened species. These efforts to restore the marine environment further contribute to positive public perception of the large-scale roll out of offshore wind.
Promoting Collaboration
Developing an offshore oyster population for the scour protection of wind turbines required fundamental knowledge of the environmental forces an oyster feature can tolerate in offshore conditions; before the project began it was unknown whether oysters could create self-sustaining reefs in an offshore environment. The project also required an industrial approach to the logistics of procuring and installing the oysters. Only by putting together a team of industry and academic partners under the auspices of the Dutch government and working with energy companies and nongovernmental organizations was the Borssele V project able to innovate at real scale.
