Biogenic reefs – reefs made up of live organisms – are important habitats for many Danish marine animals. Unfortunately, both the number and quality of our native biogenic reefs have decreased significantly over the past century, in particular in the North Sea. Banks of European flat oysters and horse mussels have been hit hard in particularly. Therefore, WWF-Denmark and Ørsted initiated a large-scale project in 2022 with DTU Aqua as the scientific partner, the aim of which is to produce oysters and horse mussels with a view to restoring biogenic reefs in the Danish part of the North Sea region, including the northern part of the Kattegat Sea.
Several locations in the Danish seas, including Anholt Offshore Wind Farm and Thyborøn Stenvolde, have been considered as the site for the project. The site selected is Hirsholmene archipelago near Frederikshavn in the northern part of Denmark, which is ideal as European flat oysters have previously inhabited the area immediately to the north, and some scattered occurrences of horse mussels can still be found in the area – an important criterion for maximising the chances of survival of the reef.
Ingrid Reumert, Senior Vice President and Head of Global Stakeholder Relations at Ørsted, says:
"This is an important project that will benefit the marine environment, increase biodiversity and improve the water quality locally in the Danish part of the North Sea – which is why we're delighted to have reached an important milestone by selecting a location for the project, allowing us to move it forward. Together with WWF, we're dedicated to setting new standards for biodiversity-promoting work related to offshore wind development, and therefore innovative projects like BioReef are necessary to enlighten us on the possibilities."
Mikkel Aarø-Hansen, Secretary General of WWF Denmark, says:
"We're in the middle of a biodiversity crisis, which we can only solve through strong partnerships and new innovative solutions. The project with biogenic reefs is a good example of that. The reefs provide food and shelter for small fish and other marine animals. Our aim is that experience from the BioReef project in the North Sea region can be applied internationally, so that we'll scale up efforts and share knowledge from our joint nature restoration project with the rest of the world."
Pernille Nielsen, Project Manager and Senior Researcher at the Section for Coastal Ecology at DTU Aqua, says:
"This is the first time an attempt has been made to create large-scale banks of horse mussels and restore oyster banks in Danish waters. Viable fry of oysters and horse mussels of a certain size must be produced in order to reach the critical mass needed to realise the project. DTU Aqua has in-depth knowledge and experience of both hatchery and distribution of e.g. mussels and oysters in Danish inland waters, which is crucial for creating the biogenic reef for the BioReef project."
However, as the creation of a biogenic reef at Hirsholmene is subject to a regulatory approval, the concrete deployment of oysters and horse mussels cannot begin until 2027 at the earliest. But experiments are already being planned with stocking in the Limfjord strait (connecting the North Sea and the Kattegat Sea) close to DTU Aqua's facilities at the Dansk Shellfish Centre, where the experiments can be monitored on a continuous basis. Initially, the experiments will be performed with the species with which we made the most progress, namely European flat oysters, and the purpose of the experiments is to test materials and various designs to ensure good growth and protect the young oysters against predators such as crabs and starfish.
The creation of the biogenic reefs at Hirsholmene is intended to contribute to developing new innovative methods for the creation of similar reefs to be used for restoration projects in many other places in the world.
About biogenic reefs
In Danish waters, biogenic reefs are created by i.a. mussels and oysters, forming a substrate and hiding places for other animals, and fulfil many ecosystem functions. These species can produce biogenic reefs, consisting of live organisms and empty shells from these organisms. Therefore, oyster and mussel fry for the biogenic reef have been collected and grown since the onset of the project.
Once created, biogenic reefs serve as a food base and hiding place from other marine animals as well as a basis for macroalgae and organisms such as corals and sea sponges that anchor to the hard surfaces of the reef. All biogenic reefs constitute a crucial part of the marine ecosystems.
About selecting the location for the BioReef project
- The location of the biogenic reef is important, and that is why WWF-Denmark and Ørsted, together with a team of researchers from DTU Aqua, have investigated where banks of oysters and horse mussels were located previously in the Danish seas. One of the biggest challenges of the project is to find an area which historically has been home to a bank, is still suitable for a biogenic reef, and is also protected from activities that could threaten the very existence of the new banks.
- The selected area at Hirsholmene near Frederikshavn has been designated a marine protected area, also known as a Natura 2000 site. Plans and projects in the area have to fulfil very strict requirements, and bottom trawling fishing only takes place on a limited scale.
- However, as the creation of a biogenic reef at Hirsholmene is subject to a regulatory approval, the concrete deployment of oysters and horse mussels cannot begin until 2027 at the earliest.
Project milestones
2023: Collecting broodstock oysters/mussels and screening historical locations with biogenic reefs in Danish waters.
2024: Selecting the location of the biogenic reef(s) in the Danish part of the North Sea region. Developing protocols for farming European flat oysters and horse mussels and testing the viability of minor reefs in coastal areas.
2025-2026: Additional testing in the hatchery and at coastal locations.
2027: Commencing creation of reefs in the Danish part of the North Sea.
Ørsted and WWF-Denmark
The marine recovery project BioReef builds on collaborations dating back to 2018, under which WWF-Denmark and Ørsted together installed 3D printed reefs at the Danish Anholt Offshore Wind Farm. The marine restoration projects support both Ørsted's ambition for net-positive biodiversity impact from new projects commissioned from 2030 and WWF's call to halt and reverse the loss of biodiversity before 2030.
You can read more at www.orsted.com/WWF and www.wwf.dk/Orsted.
For further information, please contact:
Ørsted Global Media Relations
Kathrine Ejlskov
+45 99 55 10 23
katej@orsted.com
About Ørsted
The Ørsted vision is a world that runs entirely on green energy. Ørsted develops, constructs, and operates offshore and onshore wind farms, solar farms, energy storage facilities, renewable hydrogen and green fuels facilities, and bioenergy plants. Ørsted is recognised on the CDP Climate Change A List as a global leader on climate action and was the first energy company in the world to have its science-based net-zero emissions target validated by the Science Based Targets initiative (SBTi). Headquartered in Denmark, Ørsted employs approx. 8,400 people. Ørsted's shares are listed on Nasdaq Copenhagen (Orsted). In 2023, the group's revenue was DKK 79.3 billion (EUR 10.6 billion). Visit orsted.com or follow us on Facebook, LinkedIn, Instagram, and X.
