1 out of 6Photo: Adam Ihse/TT
In the laboratory’s aquariums, lush corals glow ghostly white in the dark. But out in the sea, below the surface, there is almost only gravel and dead skeletons left.
Here are the scientists who will save Sweden’s last coral reef.
A brilliant spring sun glistens in the waters of Kosterhavet and casts sun cats against piers and boathouses. But inside the lab at Tjärnö marine laboratory outside Strömstad, it is dark.
In large aquariums, eye corals glow white in the dark. What looks like thin, light dust grains slowly swirl around in the water. It’s eggs.
– We are doing a test here to see if they develop even better in motion, says Susanna Strömberg and shows another aquarium where a kind of paddle whips around the coral embryos.
The corals in the lab are taken from the Norwegian Tisler reef. There are almost none left in Swedish waters.
– It has been in a total of six locations that we know of. On most there is only coral gravel left, says Ann Larsson, research leader for the Life Lophelia project.
For just over three years, she and her colleagues have been working on raising eye coral larvae to study the conditions under which they thrive. The goal is to re-establish them in Swedish waters – and to save the coral reefs in the Koster Sea.
Over a thousand species
Among the white underwater forests in the aquarium can be seen paper-thin barnacles, swaying sea brush worms and pale pink spiny lobsters, as big as fingernails. In the sea outside, at a depth of just over 80 meters, there are even more spectacular ecosystems adjacent to the reefs.
– There are species of all kinds. Animals of various sizes live there and find food and shelter, and they attract several species of fish that find their food there. That is why in the past fishing has been done close to the reefs, says Anita Tullrot, project manager at the county administrative board.
More than 1,300 species have been observed on eye coral reefs, a species richness fully comparable to that of tropical coral reefs.
– It is quite common that people do not know that we have Swedish coral reefs. Spreading the knowledge is part of the project, if people know they exist, they might want to preserve them, says Ann Larsson.
Two live reefs
Exactly when they disappeared is not known. There are many theories as to why. Trawling for shrimp has probably broken up the sensitive reefs, while eutrophication and sedimentation may have affected the environment in the area.
Still, hope lives on. After trawling and anchoring bans were introduced, the corals have recovered naturally in one of the locations: at the Väderöarna, which is off Fjällbacka. It is currently around 300 square meters in size.
– The corals grow about 25 millimeters per year and about ten years ago there was nothing there. So there must have been many larvae that settled, otherwise the reef would not have been able to grow so quickly, says Anita Tullrot.
Even at Säcken, north of Strömstad, there are today a few living coral colonies.
It is known that the larvae, only 0.2 millimeters in size, are found in Swedish waters. They drift with the currents from the Tisler Reef or even as far as foundations to oil platforms in the North Sea. The problem is they don’t stop.
At the two coral reefs that are alive today, there are old, dead coral skeletons left on which the larvae can attach. At the four other locations, everything is gone.
– If there is no three-dimensional skeleton left to sit on, there will be no recovery. In the other places there is coral gravel on the bottom, but nothing grows there, says Susanna Strömberg.
3D-printer rev
The plan is therefore to manufacture artificial reefs and place them in the sea, so that the larvae have something to attach to. In the lab at Tjärnö marine laboratory, which belongs to the University of Gothenburg, small plastic constructions with different cavities and structures are lined up. A 3D printer slowly prints out the latest prototype.
– We look at what materials they like, surface structures and under which conditions they can get stuck, says Ann Larsson.
In April, a final construction will be completed, and this autumn the artificial reefs will be placed in the sea – and hopefully become home to new larvae and new reefs.
The project is the only one of its kind, say the researchers.
– Attempts have been made to transplant eye corals on a small scale in some places, but this setting out reef structures that are adapted to the larvae is unique, says Ann Larsson and adds:
– It has not been done anywhere before as far as I know.
