Balticsea 2020

What controls sediment phosphorus burial in the Baltic Sea?

In the Baltic Sea large amounts of phosphorus are removed from the water column through burial in the sea bottom – a natural process that counteracts eutrophication. However, no one knows how much phosphorus is buried in the sediments in the Baltic Sea and the mechanisms controlling the burial are poorly known. In the project “What controls sediment phosphorus burial in the Baltic Sea?” these issues were looked into.

Conclusion
If the oxygen-poor areas in the Baltic Sea is increasing, it is likely that less phosphorus will be bound in the sediments, which means that more phosphorus will be available in the water layer. Where the temporary hypoxic zones are oxygenated, the accumulation of phosphorus in the sediment improves. Oxygenation of the deeper parts of the Baltic Sea would probably increase the phosphorus accumulation in sediments in the long run. However, oxygenation of the deep basins could also lead to large accumulations of bound phosphorus in bottom sediments, which would be released to the water column if oxygen conditions again deteriorated. If the deep basins is oxygenated, it is essential to maintain the good level of oxygen, otherwise the consequences for the Baltic Sea would be disastrous.

The project was financed also by the University of Utrecht (Netherlands) and Gothenborg University and by The Netherlands Organization for Scientific Research.