Wadden Sea Eutrophication: Long-Term Trends and Regional Differences

Long-term nutrient input from major European rivers into the Wadden Sea peaked in the 1980s, with subsequent declines of about 2.5% per year for total nitrogen (TN) and 5% per year for total phosphorus (TP), leading to decreasing nutrient levels but increasing N/P ratios. However, these trends are leveling out for TP. Phytoplankton biomass, measured as chlorophyll a, has also decreased since the 1980s, reaching comparatively low levels. Regional differences in eutrophication were observed, with higher chlorophyll a levels in the southern Wadden Sea and lower levels in the northern region. The study used long-term monitoring data and modeling to link these regional differences to coastward accumulation of organic matter produced in the North Sea.

van Beusekom, J. E. E., Carstensen, J., Dolch, T., Grage, A., Hofmeister, R., Lenhart, H., Kerimoglu, O., Kolbe, K., Pätsch, J., Rick, J., Rönn, L., & Ruiter, H. (2019). Wadden Sea Eutrophication: Long-Term Trends and Regional Differences. Frontiers in Marine Science, 6. https://doi.org/10.3389/fmars.2019.00370