A significant reduction of nutrients input has been achieved for the whole Baltic Sea. This assessment shows that the normalized input of nitrogen was reduced by 12% and phosphorus by 25% between the reference period (1997-2003) and 2015 (Results figure 1). The maximum allowable input (MAI) of nitrogen in this period was fulfilled in the Kattegat, Danish Straits, Bothnian Bay and Bothnian Sea (Key message figures 1 and Results tables 1a and 1b). Nitrogen input into the Gulf of Riga is below MAI but cannot be considered as fulfilled due to statistical uncertainty. MAI for phosphorus input is fulfilled in the Kattegat, Danish Straits and Bothnian Sea. The inputs to the Gulf of Finland and Bothnian Bay are below MAI but cannot be considered as fulfilled due to statistical uncertainty.
Key message figure 1. Total input of nitrogen and phosphorus to each sub-basin and the whole Baltic Sea (BAS). Trend-based estimate of total nitrogen and phosphorus inputs in 2015 (tons per year) including statistical uncertainty are compared with the maximum allowable nutrient inputs (MAI t/y, shown as a blue line). Green colour indicates that inputs during 2015 were lower than MAI, red colour when they were higher, while yellow indicates that when taking into account the statistical uncertainty of input data it is not possible to determine whether MAI was fulfilled. Note: the scales on the y-axes differ in the charts.
The input of nutrients is an indicator of eutrophication pressure on the marine ecosystem. In the Baltic Sea, the pressure is mainly driven by anthropogenic inputs of nitrogen and phosphorus to the sea.
The HELCOM nutrient reduction scheme defines maximum allowable inputs of nitrogen and phosphorous to Baltic Sea sub-basins, and inputs should not exceed these environmental targets in order to eventually obtain good status in terms of eutrophication. This core indicator presents progress in the different Baltic Sea sub-basins towards reaching the MAI.
Descriptor 5: Human-induced eutrophication is minimized, especially adverse effects thereof, such as losses in biodiversity, ecosystem degradation, harmful algae blooms and oxygen deficiency in bottom waters.
D5C1 Nutrient concentrations are not at levels that indicate adverse eutrophication effects.
Descriptor 1: Pelagic habitats
D1C6 The condition of the habitat type, including its biotic and abiotic structure and its functions (e.g. its typical species composition and their relative abundance, absence of particularly sensitive or fragile species or species providing key function, size structure of species), is not adversely affected due to anthropogenic pressures.
Descriptor 6: Benthic habitats
D6C5 The extent of adverse effects from anthropogenic pressures on the condition of the habitat type, including alteration to its abiotic and biotic functions (e.g. its typical species composition and their relative abundance, absence of particularly sensitive or fragile species or species providing key function, size structure of species), does not exceed a specified proportion of the natural extent of the habitat type in the assessment area.
HELCOM (2018) Inputs of nutrients to the subbasins. HELCOM core indicator report. Online. [Date Viewed], [Web link].
Inputs of nutrients to the subbasins HELCOM core indicator 2018 (pdf)