Oyster reefs installed in offshore wind farms

The structures, pictured, are easily transportable and can be manually placed on the seabed from the deck of a small vessel, unlike former methods, which involved large, heavy structures that had to be installed with a large, expensive crane.

This new concept is much cheaper, and underwater cameras will monitor how successful they are in terms of improving oyster numbers.

Several of the structures have now been placed within the Borssele 1&2 wind farm, which was Ørsted’s first offshore wind farm in the Netherlands with a capacity of 752MW. The oysters have a large space to inhabit – the site is 112km₂, with 94 turbines dotted throughout it, 23km off the coast of Zeeland.

Van Oord says that 150 years ago, at least 20% of the Dutch North Sea seabed was home to large oyster reefs, but today they have virtually disappeared, ‘along with the valuable ecosystem services that they once provided’.

These ‘services’ include things like filtration, habitat provision and shelter to fish and other shellfish species.

European flat oysters, conservation groups believe, are vital in restoring marine ecosystems by producing larvae, which then colonises the rocks and eventually grows into oyster reefs.

Offshore wind farms are ideal because they provide hard substrate and undisturbed seabed for this growth.

“This is how renewable energy and nature conservation can go hand in hand,” says Van Oord.

“The oysters were placed on the scour protection around the turbines during maintenance at the wind farm today,” said Karin Bilo, Senior Marine Ecologist at Ørsted. “In the years ahead, we expect we’ll see the oysters slowly growing into reefs in the wind farm. This new method moves us significantly closer to meeting our goal of restoring the oyster reefs.”

“With this innovative pilot in offshore wind farm Borssele 1&2, we are gathering valuable insights into the effectiveness of this recovery method and its scaling-up potential,” said Van Oord Product Owner Ocean Health Nienke Oostenbrink.