To boost marine life in the North Sea, 3D-printed reef structures, among others, were recently placed on the bottom. The intention is for shell banks to form on these reef structures, as they are essential for plants and animals in the sea.
A unique nature restoration project has started in the North Sea, north of Schiermonnikoog, at a depth of about 20 metres. 6,000 kilos of Norwegian flat oysters have been placed in the Borkum Stones area, including on 3D-printed reef structures. It is the first time that oyster beds are being restored in deeper parts of the North Sea. According to the initiators WWF and ARK Natuurontwikkeling, restoring oyster beds is a huge boost for life in the North Sea.
Shell banks located at the bottom of the sea are incredibly important for everything that lives underwater. Among other things, the banks that shellfish form serve as nurseries for many aquatic animals. Until the early 20th century, about 20% of the bottom of the North Sea was covered with oyster banks. These shellfish banks have largely disappeared due to overfishing, diseases and cold winters.
"Oyster beds are hotspots of biodiversity. Species diversity there is as much as 60% higher compared to adjacent sandy areas," said WWF project leader Emilie Reuchlin-Hugenholtz in a press release. "Sharks and rays deposit eggs on an oyster bank and small fish and shrimps can shelter and grow up there. The banks are an important feeding ground for predatory fish, seabirds and marine mammals."
The 3D-printed reefs that have been placed (nine in total) are composed mainly of sand. "We wanted to use something with a lower footprint than concrete and with a natural shape so that many other species can also live there, from the small shrimp to the large cod," said WWF.
'Kickstart'
Worldwide, coral and oyster beds are being restored and protected for their increased fish production, water quality, bottom stability and contribution to coastal protection. Unless a source population is present, experience shows that shellfish beds do not return on their own. Therefore, WWF and ARK, in collaboration with Wageningen Marine Research, Bureau Waardenburg and Sas Consultancy, are now bringing back oysters at several locations; to learn what the success factors of active recovery are and, in addition, to 'kickstart' wild flat oyster beds.
On the Wageningen University website, we read that the oysters were glued to the reef with a kind of epoxy clay -which is also used for coral restoration. Indeed, experience shows that shellfish beds do not return on their own unless there is an existing population to give them a kickstart. Pauline Kamermans, researcher at Wageningen Marine Research, says: "Male and female oysters actually need to be near each other to reproduce. If the current is too strong, the larvae are spread too far apart. And if there are too few oysters, the chances of successful reproduction are very low, which is why the oysters are actively returned. They can grow up on and around the 3D reef, which also protects them from currents." It is not known by whom and with what printer the reef structures were made.
Fishermen and wind farms
According to Reuchlin-Hugenholtz, the hard substrate of the Borkum Stones is very suitable for flat oysters, which also used to occur naturally here. A special feature of the pilot is that the one-hectare test site was chosen in cooperation with fishermen. There will soon be no voluntary fishing in the area. Barbara Holierhoek, Chairman of the Fishermen's Association Hulp in Nood: "Now that we, as fishermen, are involved in this project, we can observe whether, despite or thanks to all the changing conditions such as water temperature and food richness in the seawater, this experiment with the flat oysters will succeed. We can also learn from that."
A second test site in the deep part of the North Sea is the Gemini Wind Farm, near the Borkum Stones, where 1,000 kilograms of oysters and test cages are being placed. This is also the first attempt in the North Sea to start an oyster bank in a wind farm.
National Plan
Reuchlin-Hugenholtz hopes the exemplary projects will prompt the Dutch government to scale up nature restoration in the North Sea. "It would be nice if the government takes the initiative for a National Plan for Oyster Bank Restoration. This is not just about space because bottom protection in the North Sea is crucial to give shellfish beds a sustainable future. In addition, the government can play an important facilitating role in the development of revenue models in close cooperation with the shellfish sector and, for instance, the wind energy industry. In this way, opportunities for construction and sustainable management of oyster beds at sea can be cleverly exploited. A win-win situation!"
Source: WWF/WUR
Photo: Video WWF
