The Säcken reef in the Koster Fjord in Sweden is that country’s last remaining cold-water coral reef and it is under a distinct threat of extinction.
Like the more common warm-water reefs, cold-water reefs are known for their rich biological diversity.
With the Säcken reef in distress, researchers from the University of Gothenburg have started a restoration project extracting healthy corals from reefs on the Norwegian coast placing them into the Säcken reef. Sweden’s sole reef-building coral, called Lophelia pertusa, requires an environment that has a constant high level of salinity in conjunction with low water temperatures all year round.
These conditions in Sweden only exist in the northern part of Bohuslän. This is a deep water region where water from the Atlantic is led in via the Norwegian Trench.
“We’ve known since the mid-1920s that cold-water coral reefs exist here in Sweden,” says marine biologist and researcher Mikael Dahl.
“At that time, corals could be found in three locations in the Koster Fjord. Today, only the Säcken reef remains, and it’s in poor condition.”
The researchers believe the causes of distress for the reef is due to the impact of trawling along with increased sedimentation from eutrophication.
The reef, under continuous observation by remotely operated vehicles, has been observed to be in a slow and continual rate of decline.
“The red list assessment is currently in the ‘under immediate threat’ category.
The Säcken reef has been protected against trawling for more than a decade, but trawling damage has been observed on the reef several times after the legislation was set in place”, says Mikael Dahl.
The legislation referenced above was strengthened three years ago when Sweden declared their first national marine park.
The Kosterhavet National Park was created to help protect this distressed area.
Unfortunately, the Säcken reef remains in exceptionally poor condition.