Biology Oysters used to form reefs from the Mediterranean to Norway
Oysters once formed extensive reefs off the coasts of Europe. The oyster reefs stretched from Norway to the Mediterranean. According to a new study, the reefs covered at least 1.7 million hectares in total - ten times the size of the canton of Zurich.
03.10.2024, 11:00
SDA
The complex ecosystems of living and already dead oysters provided habitats for numerous other animals, as a research team reports in the journal "Nature Sustainability".
The oyster reefs were destroyed more than a hundred years ago, mainly due to overfishing, report 30 researchers from Europe. Reduced water quality, sediment deposits and the introduction of pathogens have also led to the species becoming virtually extinct in a large part of its original range.
Only a few oysters remain
Although some European oysters can still be found, they are mostly isolated in the oceans, as the study states, and hardly ever live together in clumps, banks and reefs. There are reintroduction projects in several places, for example in the North Sea off Borkum. The researchers believe that these projects should be stepped up.
According to the Alfred Wegener Institute (AWI) in Bremerhaven, which was involved in the study, oyster reefs are of similar ecological importance to coral reefs. The current study states that more species live in the limestone structures than in the surrounding areas in the sea. In addition, the oysters stabilized the coastlines and filtered water - a single oyster can pass up to 200 liters a day.
Old newspapers, nautical charts and interviews
Oyster reefs are said to have existed almost everywhere along the European coasts in the past. To find out details about their extent, the researchers looked at historical records such as newspapers, books, travelogues, nautical charts, early scientific studies, customs accounts and records of oyster licenses. The researchers found the largest concentration of oyster reefs in the southern part of the North Sea, including in Germany.
Philine zu Ermgassen from the British University of Edinburgh, one of the lead authors, explained: "Oyster reefs develop slowly, with layers of new oysters forming on the dead shells of their predecessors, but their destruction by overfishing occurred relatively quickly." This has led to a flattening of the seabed.
"We tend to think of our seafloor as a flat, muddy expanse," adds co-lead author Ruth Thurstan from the University of Exeter, "but in the past many places were a three-dimensional landscape with complex living reefs - which have now completely disappeared from our collective memory."
