The start of the oyster project
In 2018, a unique nature restoration project started in the North Sea. For the first time, oyster beds were being repaired in deeper parts of the North Sea. This effort was undertaken in order to learn the success factors for active recovery and also to 'kickstart' wild flat oyster beds. World Wildlife Fund (WWF) and ARK Nature Development initiated this project, and Gemini Wind Park also made a contribution. At the park, some 1,000 kg of oysters and test cages were placed as part of a broader programme of oyster bed repair at several locations in the North Sea. This also represented the first attempt in the North Sea of starting an oyster bank within a wind park.
Flat oyster beds used to occur on a large scale in the North Sea; until the beginning of the 20th century, about 20% of the North Sea floor was covered with oyster beds. These shellfish banks have largely disappeared due to overfishing, disease and cold winters. The banks offer a breeding ground for marine animals, support the growth of plants and animals, filter the sea water, increase fish production and contribute to coastal protection.
The richness of the species found on shellfish banks is 60% higher near sandy soils. Sharks and skates lay their eggs on the bank and small fish and shrimps can shelter and grow there. The shellfish bank is also an important breeding ground for predatory fish, seabirds and marine mammals. Shellfish banks therefore represent a fundamental, resilient and healthy North Sea ecosystem.
Cooperation The Rich North Sea
In the beginning of 2022, the project was continued when researchers from De Rijke Noordzee and Gemini Windpark joined forces to restore one of the largest oyster reefs that the North Sea had ever had.
Due to fishing, a changing seabed and diseases, the oyster reefs were lost in the last century. Oyster beds occupy an important place in underwater ecosystems. But development and restoration of oyster beds is complex, which is why research is being conducted at various locations into the conditions in which oysters and other shellfish thrive best. Wind farms seem to be a suitable location for this, because there is no fishing and the bottom is not damaged, and because there are enough hard materials for oysters to attach to.
This research in Gemini Windpark is special for three reasons: a reef of this scale has never been constructed in the Netherlands before, it is the first time that researchers from the Rich North Sea have focused on a former oyster ground and the first time that the organization has focused on the northern North Sea, above the Wadden Islands. Previous studies took place along the west coast of our country.
Preliminary research has shown that the conditions in Gemini Windpark are favorable for oyster bed recovery. The waves are lower than on the west coast of our country and the seabed is less dynamic. This means that the 'sand waves' and 'mega ripples' are lower in height and follow each other less quickly than elsewhere on the North Sea bed.
The researchers lowered more than 1,500 oysters and 18 tons of shells to the bottom of the wind farm over a total area of five hectares, about the size of eight football fields. in the summer of 2022, another 3,000 oysters, hundreds of thousands of baby oysters and 48 tons of shell material were added.
The researchers will return to the reef-in-progress several times. It is then checked whether the oysters reproduce, whether they grow, and whether they are moved or buried by waves and currents.
The second load of oysters consisted of young oysters and 'baby oysters', the so-called 'splash-on-shell', to see whether the young animals also survive. The shell material and oysters will hopefully form a reef in the coming years and attract other animals such as crabs, squid, anemones and sharks.
