Sweden’s Säcken Reef Facing Death
October 23, 2012

Säcken, Sweden’s Only Cold-Water Coral Reef, May Die

Alan McStravick for redOrbit.com — Your Universe Online

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.

Coral reefs typically are entirely dependent upon larvae from other reefs in order to recover naturally after they have been damaged. For some time, the researchers have set their hopes on larvae from the nearby coral reefs in Norwegian waters. However, a study recently published in the research journal Coral Reefs shows that the Säcken reef is too isolated from the other reefs in the northeast Skagerrak.

Through the use of genetic markers, the researchers were able to estimate the degree of gene flow between the reefs in Skagerrak. Their results show the genetic distance between the Säcken reef and four other reefs in the northeast Skagerrak is one of the largest on both sides of the Atlantic. But to be certain, the genetic diversity on the Säcken reef is also much lower than has been observed in any other reef of this type.

"This means that it is highly unlikely that the Säcken reef will recover naturally," says Mikael Dahl, who led the study. "Instead, interventions are needed in order to ensure the survival of the reef."

It was on the basis of the results of this research the team from the University of Gothenburg has started a restoration project where they are obtaining healthier corals from the nearby reefs in Norway and, after genetically characterizing them, placing them on the Säcken reef. The Gothenburg team hopes that these new corals will survive the process of being transferred, and that they will be able to help with the re-establishment of the reef, through both asexual and sexual reproduction.

The Säcken reef, at its healthiest, spread across an area of 5,000 square meters. While the skeleton of the reef still inhabits that area, today the only living coral in the area covers approximately 300-500 square meters. Another part of the study also shows that individual specimens of Lophelia pertusa corals may actually be several thousands of years old. Individual specimens in the neighboring Norwegian coral reef have been estimated to be somewhere near 6,200 years old. Many may be even older.

"In other words, it's not only the reefs themselves that are extremely old, but it's also actually the same individuals that have been situated there since soon after the withdrawal of the inland ice. These individual corals have been living there in the deep darkness since long before the Pharaohs built the pyramids", says Mikael Dahl.