New Stone Reefs in Odense Fjord Aim to Boost Biodiversity
Stone reefs are important habitats for aquatic animals. Now, two new reefs are being created in Odense Fjord, and the partners behind the project hope for improved biodiversity.
The partners in the Odense Fjord Collaboration are in the process of constructing two new stone reefs in Odense Fjord.
The reefs are built of 4,500 tons of stones, forming two reefs approximately 200 meters long, six meters wide, and 1–1.5 meters high.
"The stones have many positive qualities. They create holes and crevices that attract crustaceans, juvenile fish, and other marine life. Larger algae can also grow on the stones. Additionally, the stone reef will protect eelgrass from stress caused by waves and currents, giving it better conditions to grow. It will be exciting to follow the results," says Timi Løvholdt Banke, a Ph.D. student at the Department of Biology.
No natural stone reefs left
The stones are large quarry stones (more than 40 cm in diameter), and when stacked, they form holes and crevices where the fjord’s animals can hide. The holes in stone reefs are also attractive spawning grounds, and the stones provide a surface for seaweed to attach itself on, allowing vegetation to develop on the seabed as well.
Like many other areas in Denmark’s inner waters, the seabed in Odense Fjord today lacks natural stone reefs. Over the years, stones have been fished up for construction purposes.
This, combined with other factors—especially the discharge of nutrients—has contributed to Odense Fjord being classified as not having what biologists call "good ecological water quality."
”The fjord is our shared responsibility.
Among the partners in the Odense Fjord Collaboration who have been involved in this construction project are Odense Municipality and Nordfyn Municipality, both of which have contributed funding.
"The fjord is our shared responsibility. Stone reefs are essential for making a positive difference for the fjord, and there’s a great need for more projects like this in the future," says Tim Vermund, Odense Municipality.
In Nordfyn Municipality, Anders Thingholm, agrees.
Odense Port also contributes
"Odense Fjord is part of our identity and an important resource for Nordfyn Municipality. With this responsibility comes an obligation to contribute to the fjord's future. I strongly believe that we create the best solutions by including the local community and have all sectors work closely together," he says.
The large construction project also requires additional services, facilitation, and logistics, which another partner in the collaboration, Odense Port, provides.
"For us as a port, the fjord is a central part of our daily life. We are a partner in the Odense Fjord Collaboration because we want to contribute to positive projects like this one to improve the condition of the fjord," says Carsten Aa, Director of Odense Port.
Eelgrass seedlings
The stone reefs are just one part of the solution within the Odense Fjord Collaboration. The next step in the broader restoration plan is to establish more measures that will work in conjunction with the stone reefs and reduced nutrient discharge.
For instance, sand capping is being considered, where a several-centimeter-thick layer of sand is placed on the seabed where it is too muddy for eelgrass to grow (eelgrass naturally grows in sand). There are also plans to plant eelgrass cuttings in locations where they have a chance to survive and reproduce, leading to the formation of lush eelgrass beds. Like stone reefs, eelgrass beds are excellent habitats for juvenile fish that need places to hide.
However, funding is still needed to realize these plans.
Who are the partners?
The establishing and scientific monitoring of the stone reefs is financed by Aage V. Jensen Naturfond, Odense Municipality, Nordfyns Municipality, and Department of Biology. Odense Port supports the project. SDU manages the project with support from the Odense Fjord Collaboration.