Estimating the amount of mobile phosphorus in Baltic coastal soft sediments of central Sweden

A new dataset based on 102 sediment cores was examined to estimate the amount of phosphorus (P) that will eventually be released to the water column from the Baltic coastal sediments along the Swedish coast between Oregrund and Oxelosund. Total P (P-tot) concentration in the surface sediments varied between 840 and 7100 mu g g(-1) dry weight (dw) with an average of 1650 mu g g(-1) dw. In deep sediments, the P-tot concentration was around 1000 mu g g(-1) with small variation. The difference between surface concentration and the stable, deeper, concentration represents P to be released, i.e. the mobile P. Pools of mobile P varied between 1.5 and 18.2 g m(-2). Correlations between surface P-tot concentrations and amounts of mobile P were strong (r(2) = 0.88). We estimate the amount of mobile P in the coastal sediments of the investigated region to be between 1000 and 4000 tonnes. Assuming a turnover time of the mobile P between three and ten years gives an average annual P release of 100-1300 tonnes yr(-1).