Floating Reefs: the surprising ways in which offshore solar can support the surrounding marine ecosystem

Much of the North Sea, having been trawled for fish for centuries, nowadays consists of a barren seafloor with soft sediment. The oyster reefs that once covered the seafloor are gone.  

When a hard substrate is introduced to the marine ecosystem, mussel and other invertebrate larvae attach onto it and begin to form a community quickly. This also happens beneath our floating solar platforms: a floating reef is created! This upside-down reef is a suitable habitat for biofouling organisms, or marine growth as it is also called.  

Since first installing our pilot project in the North Sea back in 2019, we have observed extensive mussel and invertebrate communities forming on the floater undersides. Blue mussel (Mytilus edulis), polychaete worms (Platynereis dumerilii) and modest barnacle (Austrominius modestus) are some of the species recorded by our scientific partner Wageningen Marine Research (Mavraki et al. 2023). Eventually, invertebrate growth attracts grazing fish that use the floating community as a source of food and shelter. The figure (left) shows the marine growth on one of our North Sea installations.  

Eventually, these smaller fish attract predators, until a thriving fish community forms beneath the floating solar platforms in addition to the attached invertebrate populations. Through first tests with eDNA, we even found horse mackerel present, a fish species not commonly found so close to the surface, 12 km from the coast.  With each new generation of mussels, individuals that have died or fallen off during storms sink to the seabed beneath the floating infrastructure. More hard substrate is introduced in the soft sediment seabed environment. This has the potential to evolve into mussel beds, similar to the oyster beds that existed before.  

To make sure we are right in our assumptions on the ways offshore solar can support local ecosystems and cultivate hope for a healthier North Sea ecological state, we continue to monitor and carry out research with our partners. 

Sustainable Development Goal 14 | Life Below Water 

Nature-inclusivity is becoming increasingly important, both for conservation efforts and in the sustainability requirements for offshore energy projects. Research and monitoring efforts are in place to support the United Nations’ Sustainable Development Goal 14: Life Below Water. The preservation of ecosystems is key in sustainable development of marine infrastructure, and Oceans of Energy aims to support Goal 14 through targets 14.1 (Reduce marine pollution), 14.2 (Protect and restore ecosystems), 14.5 (Conserve coastal and marine areas) and 14.8 (Increase scientific knowledge, research and technology for ocean health).