Sediments on the bottom of the Baltic Sea have for centuries stored massive amounts of nutrients, especially phosphorus, originating from land. In poor oxygen conditions phosphorus leaks from the sediments and fuels eutrophication, which in turn makes the oxygen conditions worse. The Finnish marine strategy aims to achieve a good environmental status of the Baltic Sea by 2020, and to reach this goal, eutrophication must be mitigated. External loads from land still need to be reduced, but it is time to address the nutrient loads located on the bottom of the sea.
The Baltic Sea Action Group participated in a report on internal nutrient storages commissioned by Finland’s Ministry of the Environment, as part of an international consortium lead by Vahanen Environment Oy. Centrum Balticum/BALEX also took part in the report. The extensive report studied internal nutrient storages’ role in eutrophication, possible sea-based measures to fix the problem, and costs and legal aspects of adopting these measures. Sea-based measures were evaluated based on their risks and benefits, cost-efficiency, and applicability. The studied measures were oxygenation of anoxic bottoms, chemical treatment of the sediment, and dredging. The most cost-efficient method turned out to be oxygenation, which has previously been tested in lakes.
Sea is a challenging environment for rehabilitating procedures. Additionally, anoxic areas on the Baltic Sea’s bottom are large. High-quality research is needed before attempting any sea-based measures on a larger scale, as there are still risks and uncertainties. The report suggests establishing a ”Baltic Sea Scientific Centre of Excellence”, which would focus on this type of research, and could combine expertise from existing research facilities. Furthermore, the report recommends charting closed bays in the coastal area as possible test grounds for small scale pilot projects. This way potential rehabilitating measures could be examined in a controlled environment, where long-term effects would be monitored closely. The importance of international cooperation is also highlighted.
”It is very important that this report has been made. It’s an essential step as we begin to solve problems caused by internal nutrient storages, so that eventually concrete action can be taken. One of the priorities is finding new financing models for future work, both for research and actual projects”, states BSAG’s Mathias Bergman.
You can read the report here.