Report: "Nutrients in the German Wadden Sea and German Bight"

The nutrient inputs across the rivers show a decreasing tendency despite major interannual differences. Flow-standardised entries have been steadily decreasing since the mid-1980s at a rate of 2 to 3 % per year. For trend studies, nutrient concentrations in winter are best suited due to low biological activity. For phosphate and dissolved inorganic nitrogen (DIN), there is a significant decrease in winter both for the open German bay and for the Wadden Sea. The winter nutrient concentrations in the German Bay and in the Wadden Sea, standardised to the salinity 30, are significantly correlated with the flow-normalised river freight. The concentrations of phosphate in the Wadden Sea and coastal waters, which were standardised to the salinity 30, were 1.06 ± 0.05 ¿mol/L (32.8 ± 1.5 g/L P) in 2006. above the guide value of 0.6 ¿mol/L (18.6 g/L P) as defined by the BLMP for coastal waters and the Wadden Sea. The concentrations of dissolved inorganic nitrogen, which were standardised to the salinity 30, were well three times higher in 2006 at 44.7 ± 3.2 mol/L (0.63 ± 0.05 mg/L N) than the orientation values of 11 to 14 mol/L (0.15 to 0.20 mg/L N). Riverine nutrient inputs have shown a declining trend, despite large interannual differences. Since the mid-1980s, flow-normalised inputs have decreased steady at a rate of 2-3 % per year. Winter is suited for trend analyses of nutrient concentrations because biological activity in this season is low. Levels of phosphate and dissolved inorganic nitrogen (DIN) decrease significantly in winter, both in the open German Bight and in the Wadden Sea. Nutrient concentrations in the German Bight and Wadden Sea in winter, normalised to salinity 30, correlate significantly with flow-normalised riverine loads. In 2006, phosphate levels normalised to salinity 30 reached 1.06 ± 0.05 ¿mol/L (32.8 ± 1.5 g/L P) in the Wadden Sea and coastal waters, exceeding the elevated level of 0.6 ¿mol/L (18.6 ¿g/L P) set by BLMP for these waters. Concentrations of dissolved inorganic nitrogen normalised to salinity 30, at 44.7 ± 3.2 ¿mol/L (0.63 ± 0.05 mg/L N), in 2006 still were three times higher than the elevated levels of 11.14 ¿mol/L (0.15 to 0.20 mg/L N).