The SEABASED Project aims at finding solutions to the problem of internal nutrient load and eutrophication in coastal areas of the Baltic Sea

The EU-funded SEABASED Project, which studies and pilots measures for reducing the internal nutrient load in coastal bays, is now more than halfway through. Let’s dive deeper to find out how the work is progressing.

New results and inputs from stakeholder workshops will help to develop guidelines for possible future use

Along the way, we have organised workshops to consult with different stakeholders and scientists concerning the acceptability, risks, feasibility and monitoring of different seabased measures, and the potential that private companies may have for participating in the protection of the Baltic Sea through innovations. The outcomes from the workshops will help us develop guidelines for the potential practical applications of different seabased measures.

The results from the practical pilots will also be used for guideline development. For example, in Åland, nutrients have been recycled from the seabed to fields via irrigation water with good results, and no harmful effects from the slight salinity of the water have been noted so far.  The irrigation experiments and effect assessment will be continued this summer.

The nutrient-rich water that had been removed from the sea had a clear effect on grass growth. The grass in the right-hand picture was irrigated four times last summer. Picture: Annica Brink

Measures on the seabed are in permitting phase

The laboratory results for Gotland limestone in binding eutrophying phosphorus permanently into the bottom sediment have proven promising. The method is also being tested in anoxic sea bays suffering from high nutrient concentrations, and the first application was implemented in Linköping last autumn. Monitoring is ongoing, and the results from the pilot will be available later this year. The pilots in Stockholm and Turku Archipelago are in permitting phase. The potential effect of removing the sediment’s active, oxygen-consuming surface layer is planned to be tested in experimental scale during this year. The pilot measures have already been welcomed by the local community and we are hoping to be able to start the practical implementation of rest of the pilots during the summer.

Pre-treated limestone was applied to an area of 10 hectares in total in Linköping, Sweden, last autumn. Picture: County Administrative Board of Östergötland

Predatory fish have a role in controlling algae growth

The project also involves piloting measures to increase the stocks of predatory fish. Predatory fish eat smaller fish that often feed on zooplankton. When the populations of small fish are kept in check, the amount of tiny aquatic animals, i.e., zooplankton, remains large enough to consume and control the levels of microscopic algae, i.e., phytoplankton. In Åland and in the area of Östergötland in Sweden harvesting of three-spined stickleback, which preys effectively on juvenile predatory fish and spawn, is being tested, and the breeding of predatory fish is supported with artificial reefs and by creating a so-called pike factory, i.e., a coastal wetland suitable for spawning. The fish have shown interest in the reefs that were introduced last May, and the construction of the pike factory will be started this summer. The stickleback catches have been small so far, but the fishing experiments have yielded valuable information on related challenges and possible solutions for developing more efficient harvesting methods.

The SEABASED project is led by the John Nurminen Foundation, and the project partners are the Centre for Economic Development, Transport and the Environment for Southwest Finland, Government of Åland, the Åland Fishfarmers’ Association, Stockholm University and County Administrative Board of Östergötland. The project is financed by the EU Interreg Central Baltic programme. To learn more about the pilot experiments and subscribe to the project newsletter, which will keep you informed of the project’s progress, please visit the project’s website: seabasedmeasures.eu