Published 11.10.2022

Metsähallitus studies underwater natural values in the planned Korsnäs offshore wind farm area

During the summer, Metsähallitus commissioned surveys of underwater plant life and wildlife off the coast of Korsnäs, in the area designated for an offshore wind farm. The surveys relate to the upcoming environmental impact assessment (EIA).

The survey of underwater natural values covers the area earmarked for an offshore wind farm. The area is around 15 kilometres from the coast and has an average depth of 10–30 metres. At the same time, natural values were studied for alternative submarine cable routes and the cable’s proposed landing points.

The studies examine the plant life and wildlife of the seabed. Alleco Oy, which specialises in underwater nature research and environmental issues in water systems, is responsible for carrying out the studies.

Managing Director of Alleco Jouni Leinikki reports that the work began in early June with surveys of the possible landing points for the submarine cable. The area for the planned offshore wind farm was examined at the beginning of September. The material obtained will be analysed during the autumn.

Diving, video recording and wading

“We have two primary methods which we use: diving and drop cameras. A trained research diver dived down to view the vegetation found on the seabed. Based on visual observations, they also examined the quantities of animals, mussels and bay barnacles found there. At the same time, they also took samples to ensure the correct identification of algae species,” Jouni Leinikki explains.

Jouni Leinikki, who has carried out dives in the offshore wind farm area, is an experienced diver and biologist. He chose his profession at an early age, started diving when he was young, studied biology, and has now been diving for 45 years, mostly on a professional basis.

The observation sites are planned according to the available data, the map, and the shape of the seabed. The samples are examined in the laboratory under a microscope, ensuring that algal species can be accurately identified.

When studying a large area, dives alone are not sufficient. Visual observations can also be made using drop cameras. This means lowering a video camera from the boat and videoing the seabed. Such video recordings can provide a fairly good picture of the seabed plant life and wildlife, although they cannot fully replace a trained diver and physical visits to the location.

Video recording is a faster method than diving. A diver can only work a limited number of hours per day, but a video camera can be recording whenever the weather allows. Drop cameras can also cover larger areas and depths that cannot be safely studied by divers.

Around the potential landing points for the submarine cable, where the water is shallow, the seabed plant life and wildlife has been studied using both diving and wading. Two important tools for wading work are an aquascope for viewing underwater and a rake to collect samples.

The water is usually more turbid near the coastline compared to the open sea, and the vegetation reaches a maximum depth of 10 metres. In the open sea, where the water is clearer, vegetation can be found down to a depth of 15 metres. Brown and red algae typically grow in the open sea. The vegetation found close to the coast includes vascular plants and charophyte algae, which provide a home to fish and micro-organisms.

Results to be analysed during the autumn

Once the dives and video recordings have been completed and the samples collected, the analysis-related work can begin. Once the data has been processed, the results of the studies can be included in the EIA process.

“No part of the seabed is completely ordinary, as nature always varies. The northern Bothnian Sea is very interesting because it is the cleanest of our coastal areas and has the clearest water. These qualities, combined with its high salinity, help marine species to thrive along its coastline. The diving sites featured plenty of Battersia arctica, a commonly found brown algae, and it seemed to be faring well. From the biological perspective, the water area is in good condition,” Jouni Leinikki concludes.

For further information, please contact:

Jaana Mursu, Leading Expert, Metsähallitus Property Development, tel. +358 206 394 015, jaana.mursu(at)