Port of Rotterdam marks a step towards restoring oyster reefs in the North Sea

On 2 September, at least half a million European flat oysters will be released in the port of Rotterdam as part of a new pilot project.

This is the first trial of an innovative new method that combines nature restoration with the installation of maritime infrastructure, such as wind turbines, breakwaters and subsea cables. Young oysters are seeded onto foundations and other infrastructure components on land before these are installed at sea.

A consortium of companies, research institutes and nature organisations aims to use this approach to restore oyster reefs in the North Sea on a large scale. Oyster reefs have become rare, even though oysters are keystone species that support biodiversity. They build reefs, filter the water and provide habitat and food for countless other animals.

Under the remote-setting method being trialled, millions of oyster larvae are reared in a specialised hatchery and then transferred to a location near the sea, such as a port. There, they are placed in shipping containers filled with seawater and stones.

Within days, the larvae attach themselves to the stones and begin developing into young oysters. The consortium is also investigating how reef sounds affect this process. Do European flat oysters use these sounds to locate a suitable place to settle? If so, the sounds could be used to increase the likelihood of successful settlement.

After several weeks, the containers are loaded aboard vessels. The stones carrying the young oysters are then deposited at sea, where the oysters establish their new habitat. If this modular and flexible approach proves successful, the process could be carried out cost-effectively anywhere and at any scale. By incorporating oyster-stones directly into the design, construction and maintenance of infrastructure such as wind farms, subsea cables, breakwaters and platforms, the project partners are combining maritime infrastructure with large-scale nature restoration.

Over the coming months, researchers will monitor the survival and growth of the released oysters. Next year, the project partners will also test the remote-setting method at a TenneT cable crossing offshore.

The development of the new technique is closely connected with the pressure facing marine life in the North Sea. As oysters grow together over time, they form large reef structures underwater. These reefs provide a solid foundation full of nooks and crannies, creating an ideal habitat for numerous species of animals and plants. Oysters also filter the water, release nutrients and remove waste materials from the water column. In doing so, they can give marine life in the North Sea a significant boost. Overfishing, pollution and disease have caused oyster reefs to disappear almost entirely from the North Sea. The remote-setting method could make an important contribution to their recovery.

The project builds on the expertise of nine partners: Wageningen Marine Research, Wageningen University, ARK Rewilding Netherlands, Stichting Zeeschelp, Waardenburg Ecology, Van Oord’s Ocean Health initiative, TenneT, Port of Rotterdam Authority and De Rijke Noordzee. De Rijke Noordzee is a collaboration between Stichting De Noordzee and Natuur & Milieu. Over the next three years, this consortium of companies, research institutes and nature organisations will work together to develop the remote-setting method further.

Pauline Kamermans, project lead for the remote-setting project at Wageningen University & Research, explains: ‘This method means that we do not have to remove adult oysters from the wild. We work with larvae that attach themselves to stones, enabling us to release large numbers of oysters in a short period. This makes transportation much easier and creates an opportunity to restore oyster reefs on a large scale.’

‘The port of Rotterdam is a place where industry and nature coexist,’ says Eric van der Schans, Director Environmental Management at Port of Rotterdam Authority. ‘The Port Authority cares for nature and is actively committed to preserving and further developing nature and biodiversity in and around the port area. The trial involving the remote settlement and monitoring of oysters temporarily released in the port fits seamlessly with this approach.’

There is a surprising amount of nature in the port of Rotterdam, from oysters and unusual orchids to seals and pipistrelle bats. These remarkable port residents can be found on the Rozenburg Landtong, in the Bird Valley and Geuzenbos, at Groene Poort tidal park, and in unexpected places right in the midst of industry.

When developing the port, Port of Rotterdam Authority carefully considers protected plant and animal species, ecological values and biodiversity. This requires expert management and carefully considered decision-making, ensuring that the Port Authority takes full account of the quality of the living environment.