Underwater exploration at Alku Reef reveals uncharacteristic deep structures for the Baltic Sea

Author
Nature Conservation Agency

October 23, 2024

During a survey of Alku Reef in the Baltic Sea, where researchers are conducting scientific investigations, it has been concluded that the project LIFE REEF, led by the Nature Conservation Agency, is carrying out research in Latvia's exclusive economic zone in the Baltic Sea. Observations at Alku Reef have revealed that the underwater structures in this area are markedly different from other locations in the Baltic Sea, as typical rocky seabeds give way to features resembling urban infrastructure.

“The underwater structure of Alku Reef resembles a small town. Specifically, the glacially deposited moraine clay exposures, several meters high, and the valleys formed between them resemble city blocks and streets. There are also isolated high-rise structures and large, paved areas overgrown with rich mussel beds. These mussel beds and smaller moraine formations have become favored habitats for urban dwellers—flounders, cod, flatfish, and other living organisms. I have not encountered such underwater landscapes and volumes in any previous studies in the Baltic Sea,” reveals Ingrīda Andersone, a leading researcher at the Latvian Institute of Hydroecology, who has seen the underwater infrastructure firsthand.

Alku Reef is located near Pāvilosta and is a pilot area for the LIFE REEF project, which studies the EU-designated specially protected habitat of Rock Reefs in the sea. This year, multiple video observations and diving work have been conducted at Alku Reef to collect samples of living organisms. The work was carried out by project partner and underwater habitat assessor, the Latvian Institute of Hydroecology.

Underwater video footage is available on the LIFE REEF project’s channel. Fieldwork in the reef area has been completed, and the next steps will involve processing the collected living organism samples and evaluating the habitat's quality and sustainability. The acquired underwater video material and the information visible in it will be used to prepare scientific justification for determining the boundaries of protected marine areas and for developing a conservation plan to justify the need for management actions to preserve natural values.

The Rock Reefs habitat (code 1170) is one of the most significant and ecologically important habitat types in the eastern Baltic Sea, characterized by hard substrate areas (rocks, boulders, pebbles) with sand deposits. This habitat serves as a crucial spawning ground, nursery, and feeding area for fish. Additionally, areas where this habitat is found underwater are notable for their substantial waterfowl feeding and concentration zones.

The Nature Conservation Agency is implementing the LIFE REEF project, titled “Research on Marine Protected Habitats and Determining the Necessary Conservation Status in Latvia's Exclusive Economic Zone,” as the leading partner in collaboration with the Institute of Food Safety, Animal Health and Environment "BIOR" and the Latvian Institute of Hydroecology.

During the LIFE REEF project, it is planned to map and study the EU-designated specially protected marine habitats of Sand Reefs and Rock Reefs in an area of 4,116 square kilometers in the Baltic Sea. More information is available on the website reef.daba.gov.lv.

Photo: Nature Conservation Agency