Indicator: Eutrophication of the North Sea/Baltic Sea by nitrogen

A graph shows the change in concentration of total nitrogen in all the main rivers which enter the North Sea and Baltic Sea in Germany. For the North Sea and Baltic Sea a flow-weighted mean over all rivers is shown. Click to enlarge
Concentration of total nitrogen in main tributaries of the North Sea and Baltic Sea ...
Source: German Environment Agency according to the Federal States and River Basin Communities Figure as PDF

Table of Contents

 

At a glance

  • To achieve the objectives for the protection of the marine environment, Germany has committed to comply with maximum concentrations of nitrogen at river mouths.
  • Averaged over all rivers, the target concentrations in the North Sea as well as in the Baltic Sea are exceeded.
  • In order to achieve further reductions in nitrogen concentrations in the rivers, measures need to be taken, particularly in agriculture.
 

Environmental importance

Coastal and transitional waters of the German North Sea and Baltic Sea fail to achieve good environmental status. The main cause of this are the excessive nutrient loads of nitrogen and phosphorous (eutrophication). The negative effects of eutrophication are described by the indicator ‘Ecological status of transitional and coastal waters’.

Nutrients are carried into the sea mainly via rivers. This indicator looks at the concentration of nitrogen in rivers which flow into the North Sea and Baltic Sea in Germany (the Rhine and Odra are therefore excluded). These concentrations can fluctuate significantly depending on the weather, because in years with plentiful precipitation more nitrogen is leached out of the soils. In terms of the nutrient phosphorous, it can be assumed that the achievement of the guideline values that have been set for rivers is sufficient for the achievement of good status of the coastal and marine waters (cf. ‘River eutrophication by phosphorus’).

 

Assessing the development

Under the EU Water Framework Directive (WFD) and the EU Marine Strategy Framework Directive (MSFD), Germany is obliged to avoid excessive eutrophication of the German North Sea and Baltic Sea. In addition, under the Baltic Sea Action Plan (HELCOM 2007), Germany is obliged to reduce the input of nitrogen into this sensitive inland sea.

In order to achieve these objectives, the German Surface Waters Ordinance (cf. water protection policy in Germany) sets what are known as management target values for the rivers running into the North Sea and Baltic Sea (OGewV 2016, in German only): 2.6 milligrammes of total nitrogen per litre (mg/l) for rivers flowing into the Baltic Sea and 2.8 mg/l for those flowing into the North Sea. These target values were also used for the German Sustainable Development Strategy (Federal Government 2016).

However, the average concentrations have dropped significantly since. This is mainly a result of the improvement in waste water purification in sewage treatment plants. The main responsibility for achieving these target values lies with the Federal States. Measures to reduce the input of nutrients are being taken as part of the implementation of the WFD. Currently most pollution comes from agriculture. The amendment to the German Fertiliser Application Ordinance will lead to a reduction in this pollution in the medium term (cf. ‘Agricultural nitrogen surplus‘ indicator). It is likely that additional measures will be needed in agriculture in order to achieve the target values.

 

Methodology

The Federal States where the rivers flow into the North and Baltic Seas maintain measuring stations at the estuaries. The nitrogen concentration of each of the flowing waters is measured at these stations at least once a month. These values, recorded over the period of a year, are used as the basis for the indicator. In order to compensate for annual weather-related fluctuations, the indicator is calculated as the moving average of the last 5 years.

More detailed information: 'Flusseinträge und direkte Einträge in die Nordsee' and 'Flusseinträge und direkte Einträge in die Ostsee' (in German only).