A range of policies, strategies and management measures have been applied to mitigate nutrient loads and combat eutrophication in the Baltic Sea region. Yet, mitigation results remain unsatisfactory due to the well-recognized but still unmanaged contribution of nutrient legacies in addition to the active sources to inland, coastal and marine waters in this region. Stockholm University, the lead partner for the Swedish MAL3 case in COASTAL, has outlined a quantitative typology approach to nutrient source attribution across the whole Swedish Baltic coast, that is capable of differentiating between active and legacy nutrient sources. Analysis has indicated dominant legacy source contributions to the monitored nitrogen and phosphorus loads in the Swedish coastal catchments with higher concentrations than the active sources. Legacy concentrations also change more slowly than nutrient concentrations from active or mixed sources over time, and are found to be well-correlated with key indicators of human activity at catchment scale, such as agricultural land share and population density. Such nutrient source distinction can support the selection of effective mitigation measures and their implementation location to reduce waterborne nutrient loads, associated eutrophication and their adverse impacts on aquatic ecosystem status on local/national level of the Swedish Baltic coast and on regional/international level of the whole Baltic Sea region.
Read the full open-access published article here: https://doi.org/10.1002/hyp.14284