A ship in the North Sea had an impressive group of passengers on board last week: 5 million tiny clams. One by one, baskets of oysters, linked by a chain, fell from the back deck to the sea floor. The procedure is an initiative by ARK Reconstruction and wind farm builder Oersted, with the goal of these oyster larvae eventually developing into living corals.
“A real experience,” Marijke van de Stack, head of the Oyster Bank Project at ARK, calls the day at sea. She and her crew were donning lifejackets and anxiously watching the baskets slide off the deck. We’ve been experimenting for years, but this is the first time we’ve been able to do it on such a scale.
Oysters are deposited in the Voordelta, a shallow marine area off the coasts of South Holland and Zeeland. Oyster larvae attached to old oyster shells, which were bound together in baskets of biodegradable material. Wooden platforms keep beehives together and away from predators. At some point, the clams will be so large that they will burst from this protective structure, hopefully forming a mature coral reef.
European flat oysters were used in this pilot project. At the beginning of the last century the bottom of the North Sea was still covered with coral reefs full of these native species, but due to intensive fishing and the use of trawl nets, only a fraction of this remains. “The soil now looks more like a field that is constantly being plowed, so the corals don’t have a chance to develop,” says Van de Stack. While they form the basis of all marine life: coral reefs provide shelter, food, protection and act as a nursery.
Pauline Kamermans is a research marine ecologist at Wageningen Marine Research and a “shellfish specialist”. She is not involved in this project, but is excited about the initiative. “Recovery of flat-topped oysters in the North Sea has developed strongly in recent years,” says Kammermans. It is exactly the technique used now, in which the shell is filled with larvae, which has already shown good results in previous small-scale experiments. Since it has never been applied to such a large scale before, it is exciting to see what the outcome will be.
Promote biodiversity
Ørsted, which builds and develops offshore wind farms, is financially supporting the project. The company has already installed artificial reefs at its Borssele 1 & 2 wind farms, with the aim of developing cod and crabs, says a spokesperson. That sounds promising. By supporting these initiatives, we hope to enhance biodiversity and develop more projects like this on future wind farms.
It remains exciting whether the young oysters will survive. A major storm or a visit from hostile crabs can partially destroy a growing coral reef. It takes about two years for oysters to reproduce, says van de Stack. Then we will know if they reproduce. Nature must now take care of it herself.
