European coastlines were once home to massive oyster reefs, which enhanced biodiversity and stabilized the coastline. Oyster populations have declined for centuries due to overfishing, and restoration initiatives are now critical to restoring these important habitats.
New research shows that oysters once formed extensive reefs along much of Europe's coastline, but these complex ecosystems were destroyed more than a century ago.
The study, based on documents from the 18th and 19th centuries, reveals that European flat oysters form large coral reefs composed of live and dead shells, providing habitat for rich biodiversity.
Today, these oysters exist mostly as scattered individuals, but researchers have found evidence of oyster reefs almost everywhere from Norway to the Mediterranean, covering an area of at least 1.7 million hectares, an area larger than Northern Ireland.
The research was led by the Universities of Exeter and Edinburgh.
Native oyster reefs create their own ecosystems filled with diverse underwater life - they support more species than the surrounding areas. In addition to creating homes for nearly 200 recorded species of fish and crustaceans, oysters play an important role in shoreline stabilization, nutrient recycling and water filtration, with a single adult oyster filtering 200 liters of water per day.
Restoration projects are taking place across Europe – small-scale habitat restoration projects such as the Wild Oyster Project, led by ZSL and its partners, are important building blocks for the return of these important ecosystems on an international scale.
However, recovery efforts need to be scaled up with the support of governments and other policymakers across the continent.
Dr Ruth Thurstan from the University of Exeter said: "Human activity has impacted the oceans for centuries, making it difficult to discover what our marine ecosystems looked like in the past, which in turn hinders conservation and restoration. Today, few people in the UK have seen the flat oyster, which is native to us. species. The oysters are still present in these waters, but they are scattered and the reefs they built are no longer there. We tend to think of the seafloor as a flat, muddy expanse, but in the past many places were three-dimensional landscapes of complex living coral reefs that are now completely lost from our collective memory," she said.
Due to their economic and cultural significance, oysters feature prominently in historical records, including newspapers, books, travel notes, landing records, nautical charts, early scientific surveys, and interviews with fishermen.
Dr Thurstan is mapping past ocean changes as part of the Convex Seascape Survey.
"We found that the greatest concentration of oyster reefs is in the North Sea. Records show that large numbers of oyster reefs exist along the coastlines of modern France, Denmark, Germany, the Netherlands, the Republic of Ireland and the United Kingdom." Dr. Philinezu Ermgassen, Honorary Research Fellow at the University of Edinburgh, said: " Oyster reefs grow slowly, with new oysters piling up on top of the dead shells of their predecessors, but overfishing destroys them relatively quickly, causing a fundamental reorganization and 'flattening' of our seafloor - removing thriving ecosystems and leaving behind vast expanses of soft sediment."
"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 are large areas with thick oyster crusts and crawling with other marine life."
Compiled from/SciTechDaily