Species in the Spotlight: Biogenic Reefs

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When people think about reefs, colourful coral reefs drenched in tropical sunlight often come to mind. But beneath the waves lies another group of remarkable habitats that are just as important: biogenic reefs.

Biogenic reefs are physical structures formed by living organisms. They are biodiversity hotspots and provide homes, shelter and feeding grounds for countless marine species. Although they may not receive the same attention as their tropical counterparts, they play a vital role in supporting healthy and productive seas.

As offshore wind continues to expand, interest is growing in how these valuable habitats can be protected, restored and, where appropriate, encouraged to recover alongside renewable energy development.

What are biogenic reefs?

A biogenic reef is a reef created by living organisms. These reefs develop over time as animals or plants build structures that become habitats for other marine life.

In Irish, UK and European waters, some of the best-known examples include:

• Native oyster (Ostrea edulis) reefs
• Horse mussel (Modiolus modiolus) beds
• Ross worm (Sabellaria spinulosa) reefs

Healthy biogenic reefs also contribute to wider ecosystem health by filtering water, stabilising sediments and supporting nutrient cycling and fisheries. Unfortunately, many of these habitats have declined significantly over the past century due to trawling, overfishing, pollution and coastal development.

Offshore wind and reef habitats

At first glance, offshore wind farms and sensitive marine habitats might seem unrelated. But as offshore infrastructure becomes a long-term feature of our seas, researchers are increasingly exploring how renewable energy development and nature recovery can work together.

Turbine foundations create hard surfaces in areas that are often dominated by soft sediment. These new structures are quickly colonised by mussels, anemones, barnacles and seaweeds, in what's often called the "artificial reef effect". Over time, these communities can attract fish, crustaceans and larger predators, increasing the local biodiversity around the foundations.

While artificial reefs are not the same as natural biogenic reefs, they demonstrate how offshore structures can provide habitat and influence ecosystem processes. This has prompted scientists, developers and conservation organisations to investigate whether offshore wind farms could also support the recovery of native reef-forming species.

Importantly, this does not mean every wind farm automatically creates ecological benefits. Outcomes depend on site conditions, species present, design, construction methods and long-term management. The goal is not simply to add habitat, but to support functioning ecosystems that complement existing marine environments.

Supporting nature recovery

One of the most exciting areas of research focuses on restoring native oyster reefs within offshore wind farms.

Across the North Sea, researchers are exploring techniques such as introducing suitable reef material, deploying settlement structures for juvenile oysters and designing restoration methods that work alongside offshore infrastructure.

One example is Ørsted's BioReef initiative, run with WWF Denmark and DTU Aqua, which is developing hatchery-based methods to breed European flat oysters and horse mussels for reef restoration, with reef creation in the Danish North Sea targeted for 2027. Pilot projects like this are helping build evidence on what works, what doesn't, and how restoration can be integrated into offshore developments in a practical way.

Building biodiversity into offshore wind

The offshore wind industry is increasingly considering how biodiversity can be incorporated throughout the lifecycle of projects, exploring nature-positive approaches that go beyond avoiding environmental impacts and instead seek opportunities to support ecosystem recovery where appropriate.

These approaches are still evolving, and many require continued research and careful evaluation. However, collaboration between developers, scientists, regulators and conservation organisations is helping improve our understanding of how renewable energy and marine conservation can co-exist.

Looking ahead

The transition to renewable energy presents an opportunity not only to reduce carbon emissions but also to think differently about how we manage our oceans.

Biogenic reefs remind us that even relatively small marine organisms can shape entire ecosystems. By protecting existing reefs and exploring opportunities for carefully planned restoration, offshore wind projects may contribute to healthier, more resilient marine environments.

There is still much to learn, but one thing is clear: understanding these remarkable habitats is becoming an increasingly important part of the conversation around offshore wind. As research continues and restoration projects develop, biogenic reefs are certainly a habitat to keep in the spotlight.