TenneT, the Dutch electricity transmission system operator, has taken a significant step in promoting nature-inclusive construction by installing artificial reefs near the offshore transformer platform, Hollandse Kust West Alpha. This platform will serve as a vital link between the Ecowende consortium's (comprising Shell and Eneco) wind farm and the high-voltage grid. In partnership with contractor Equans/Smulders, TenneT's goal is to develop the site while minimizing its impact on the environment. The deployment of artificial reefs is part of a broader ecological initiative by TenneT aimed at monitoring and enhancing underwater ecosystems around offshore wind farms.
Saskia Jaarsma, the Head of Offshore Development at TenneT, acknowledges the potential environmental impact in the North Sea. Jaarsma states, “We are aware of the potential impact on the North Sea. That's why we pay a lot of attention to researching what happens underwater. The installation of artificial reefs is another step in researching, monitoring, and stimulating marine life.”
The installation consists of two types of artificial reefs situated near the Hollandse Kust West Alpha jacket, located approximately 50 kilometers off the coast of Egmond aan Zee. In the case of one structure, six reef cubes are attached to a frame. These cubes are hollow square blocks crafted from nature-friendly recycled materials, featuring round holes in the walls. The other structure comprises six reef balls, designed in the shape of a ball, providing similar opportunities for marine life to thrive.
Marine biologist and TenneT advisor Annemiek Hermans explains the purpose of these artificial reef structures, stating, “These artificial reef structures are meant to stimulate marine life. With these, you create potential spots where coral and algae settle. Earlier research shows that fish, crabs, and lobsters like to visit these spots for shelter and to look for food.”
The trial aims to investigate which shape, either the ball or cube, proves more effective. The hollow design of the cubes offers protection for young fish while also increasing the structure's bonding surface, ultimately providing a suitable habitat for various animal and plant species in addition to juvenile fish, crabs, and lobsters.
According to Jaarsma, “Only in this way can you gain the necessary knowledge and experience to build nature-inclusively. Otherwise, you never find out what the success rate of a measure is. These pilots are relatively intensive to realize but of great value for ecology. For example, the first effects of the ecological cable crossings at wind farm Hollandse Kust Zuid are already surprisingly good; we see a lot of life developing there.”
Hermans expects that it may take up to three years before the visible differences resulting from this initiative become apparent. “Until then, we monitor annually whether the diversity of life forms around the artificial reefs and fish hotels increases,” she stated. “Fish lose scales and cells, for example, and feces also end up in the water. By reading DNA in water samples, you can find out pretty quickly which guests have checked in.”