This finding is in line with previous research done on trends in N AZD6244 mouse and P in Estonian rivers (Iital et al., 2005). Iital et al. (2005) found a downward trend in the amount of N in 91% of the studied sites while a downward

trend in the amount of P was observed in only 9% of the studied sites while also some upward trends were observed (9% of the studied sites). Table 2 and Fig. 3 show that there is a lot of variability between the catchments in both east and west. The regional variation in trends can prove interesting for management strategies that aim to reduce nutrient loads into the Baltic Sea. The focus should be more on catchments experiencing an increasing trend or no trend at all. Previous modelling studies projecting future changes of nutrient loads into the Baltic Sea focused on the entire basin-scale (Arheimer et al., 2014, Donnelly et al., 2014, Meier et al., 2012 and Meier et al., PTC124 2014). These modelling studies and their findings are often considered by policy makers to implement management strategies. Since our study demonstrates that large variation exists among the catchments, it can be suggested to look more at catchment-scale interactions when developing management strategies. This might reveal additional information which can lead to more focused and effective approaches to reach targeted reductions. The results

in Table 2 show the potential for nutrient reductions in the BSDB. Upscaling the 0.13 kg km−2 yr−2 reduction in TP observed in 13% of the total BSDB area (east + west) results in a potential reduction of 223 tonnes per year. Considering a similar upscaling for TN, there is a potential reduction of 10,980 tonnes per year. Target reductions GNA12 set by the Baltic Sea Action Plan (BSAP) correspond to a reduction of 135,000 tonnes TN and 15,250 tonnes TP by 2021 (HELCOM, 2007). If we assume these potential reduction rates for TN and TP, then the target reduction of TP would be reached in 68 years while the target reduction of TN would be reached in 12 years. Although it is unlikely that change rates calculated for the year 1970–2000 will be the same for 2000–2021, these

estimates suggest it is possible to reduce TP in the BSDB but that it will be difficult to reach the target reductions by 2021 without significant shifts in land management. Table 2 and Fig. 3 also show that the focus for management strategies should be more on P reduction rather than on N reduction as more catchments show an increasing trend rather than a negative trend for TP. This suggestion is further reinforced when the N:P ratio is taken into account. The N:P ratio steadily declined in eastern catchments from 30 to 16, which will ultimately affect the N:P ratio for the whole Baltic Sea. The results presented in this study suggest that a declining trend in N:P ratio is largely caused by an increase of TP from eastern catchments.