By Stephen Beech via SWNS
Oyster reefs once thrived along hundreds of miles of Britain and Europe’s coastline – covering an area larger than Northern Ireland, reveals a new study.
Researchers have discovered evidence of reefs almost everywhere – from Norway to the Mediterranean – covering at least 1.7 million hectares (4.2 million acres).
Based on documents from the 18th and 19th Centuries, the study reveals that European flat oysters formed large reefs of both living and dead shells, providing a habitat supporting rich biodiversity.
But the “complex” ecosystems were destroyed over a century ago, and today oysters in the same waters are mostly found as scattered individuals.
The new study, led by researchers at Exeter and Edinburgh Universities and published in the journal Nature Sustainability, reveals that native oyster reefs created their own ecosystems, full of a diverse range of underwater life – supporting a greater number of species than surrounding areas.
As well as creating homes for almost 200 recorded fish and crustacean species, scientists say the oysters also played a “vital” role in stabilizing shorelines, nutrient cycling and water filtration – with a single adult oyster filtering up to 200 liters of water a day.
Restoration projects are now underway around Britain and Europe.
Conservationists say small-scale habitat restoration, such as The Wild Oyster Project in the UK, are key stepping stones to the return of the ecosystems on an international scale.
But they warned restoration efforts need to be scaled up with support from governments and other decision makers across the continent.
Dr. Ruth Thurstan, of the University of Exeter, is part of the Convex Seascape Survey, an ambitious five-year project examining ocean carbon storage.
She said: “Human activities have affected the ocean for centuries.
“This makes it difficult to discover what our marine ecosystems used to look like, which in turn hampers conservation and recovery.
“Few people in the UK today will have seen a flat oyster, which is our native species.
“Oysters still exist in these waters but they’re scattered, and the reefs they built are gone.
“We tend to think of our seafloor as a flat, muddy expanse, but in the past many locations were a three-dimensional landscape of complex living reefs – now completely lost from our collective memory.”
Dr. Thurstan says that, due to their economic and cultural significance, oysters feature in historical records including newspapers, books, travel writing, landing records, nautical charts, early scientific investigations and interviews with fishermen.
She said: “By combining descriptive accounts from a range of historical sources, we can build a picture of our past seas.
“The greatest concentration of oyster reefs we found was in the North Sea.”
Records show extensive reefs existed along the coasts of the UK, Ireland, France, Denmark, Germany and the Netherlands.
Dr. Philine zu Ermgassen, an honorary researcher at the University of Edinburgh, said: “Oyster reefs are slow to develop, with layers of new oysters building up on the dead shells of their predecessors, but their destruction through overfishing was relatively rapid.
“This has caused a fundamental restructuring and ‘flattening’ of our seafloors – removing thriving ecosystems and leaving an expanse of soft sediment behind.”
She added: “Thanks to this historical ecology research, we are now able to quantitatively describe what oyster reefs looked like before they were impacted, and the spatial extent of the ecosystems they formed.
“These were huge areas that were thickly crusted with oysters and crawling with other marine life.”
