Oyster reefs once thrived along European coasts, study reveals. Today they are gone

Oysters once formed vast reefs along much of Europe’s coastline, but these complex ecosystems were destroyed more than a century ago, new research shows. The article, published in the journal Sustainability of natureis titled “Archives reveal the vast historical extent of European oyster reef ecosystems”.

Based on documents from the 18th and 19th centuries, the study reveals that European flat oysters formed large reefs of living and dead shells, providing a habitat supporting rich biodiversity.

Today, these oysters are found mostly as scattered individuals, but researchers have found reefs almost everywhere, from Norway to the Mediterranean, covering at least 1.7 million hectares, an area larger than Northern Ireland.

The research was led by the University of Exeter and the University of Edinburgh.

Native oyster reefs have created their own ecosystems, filled with diverse underwater life, supporting greater numbers of species than surrounding areas.

In addition to creating habitats for nearly 200 recorded species of fish and shellfish, oysters have also played a vital role in shoreline stabilization, nutrient cycling and water filtration, with a single adult oyster filtering up to ‘to 200 liters of water per day.

Restoration projects are underway across Europe and small-scale habitat restoration, such as the Wild Oyster project, led by ZSL and partners, is a key step towards returning these vital ecosystems to scale. international.

However, restoration efforts must be scaled up with the support of governments and other decision-makers across the continent.

“Human activities have affected the ocean for centuries,” said Dr Ruth Thurstan, from the University of Exeter and a member of the Convex Seascape Survey, an ambitious five-year project examining carbon storage in the oceans.

“This makes it difficult to discover what our marine ecosystems look like, hindering conservation and recovery.

“Today, few people in the UK will have seen a flat oyster, which is our native species. Oysters still exist in these waters, but they are scattered and the reefs they built have disappeared.

“We tend to think of our seabed as a flat, muddy expanse, but in the past many places were a three-dimensional landscape of complex living reefs, now completely lost from our collective memory.”

Because of their economic and cultural importance, oysters feature in historical records, including newspapers, books, travel writings, landing records, nautical charts, early scientific surveys, and interviews with fishermen.

“By combining descriptive accounts from a range of historical sources, we can build a picture of our past seas,” said Dr Thurstan, who maps past ocean changes as part of the Convex Seascape Survey.

“The largest concentration of oyster reefs we found was in the North Sea.”

Records show that extensive reefs existed along the coasts of France, Denmark, Germany, the Netherlands, the Republic of Ireland and the United Kingdom.

“Oyster reefs grow slowly, with layers of new oysters accumulating on the dead shells of their predecessors, but their destruction by overfishing has been relatively rapid,” said Dr Philine zu Ermgassen, honorary researcher at the University of Edinburgh.

“This has caused a fundamental restructuring and ‘flattening’ of our seabed, removing thriving ecosystems and leaving behind an expanse of soft sediment.

“Thanks to this research in historical ecology, we are now able to quantitatively describe what oyster reefs looked like before they were impacted, as well as the spatial extent of the ecosystems they formed.

“These were large areas covered in a thick crust of oysters and teeming with other marine life.”

The research team consisted of more than 30 European researchers from the Native Oyster Restoration Alliance.