Nutrients in Europe's transitional, coastal and marine waters (Indicator)

Key messages: Eutrophication is still a large-scale problem in the Baltic, Black and Greater North Seas and some coastal areas of the Mediterranean. Nutrient levels declined significantly between 1980 and 2021 but eutrophication remains an important problem. Although progress has been made in reducing inputs of some nutrients, particularly nitrogen, further efforts are necessary, especially for phosphorus reduction.

Number of time series available showing trends in dissolved inorganic nitrogen and orthophosphate concentrations for each regional sea during the period 1980-2021

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Eutrophication in marine waters occurs when excessive nutrients, primarily nitrogen and phosphorus, enter the ecosystem. Many nutrient sources, such as agriculture runoff and wastewater discharge, result from human activities (EEA, 2019). This excessive availability of nitrogen and phosphorus accelerates the growth of microalgae. Algal blooms associated with eutrophication can produce toxins that harm or kill marine organisms and consume oxygen that is necessary for marine life.

Nitrogen concentrations in the Greater North and Baltic Seas have decreased during the last 4 decades, reflecting the effect of EU policy implementation on reducing nutrient inputs. The increasing trends in phosphorus concentrations observed in some parts of the Baltic Sea are likely to be related to the release of phosphorus from sediment under anoxic conditions. Decreasing trends are observed in the Greater North Sea.

For both nitrogen and phosphorus, no clear trends can be identified in some regional seas because of limited time series data.

Please consult the relevant indicators and signals below for a more comprehensive overview on the topic.

Unlikely: Nutrients show a mixed trend. The EU is currently not on track to meet the zero-pollution target and MSFD good environmental status target (EU, 2008) in terms of nutrients. Besides, achieving the zero-pollution target of reducing nutrient losses by 50% depends mainly on curbing the sources of pollution from soil and rivers. Seas are sinks for nutrient pollution and the positive impacts of curbing pollution at the source can be observed later within them.

This indicator looks at trends in concentrations of dissolved inorganic nitrogen (DIN: the sum of ammonium, nitrite and nitrate) and orthophosphate in the upper 10m of the water column in Europe's seas during the season of low phytoplankton growth (SLPG) for the period 1980-2019. Data were aggregated into squares of 0.01 degree latitude × 0.01 degree longitute for coastal stations (within 20km of the coastline) and 0.05 degree latitude × 0.05 degree longitute for open water stations. The SLPG was considered to be August to October in the Mediterranean and Black seas, January to March in the Baltic Sea and January to February in the other regional seas. Temporal trends were estimated using the non-parametric Mann-Kendall test. Only stations with data for at least 5 years and over the 2015-2019 period were considered. A p-value of <0.05 was considered to indicate a statistically significant trend. For more information please visit the EEA indicator page.

References and footnotes

EEA, 2019, ‘Nutrient enrichment and eutrophication in Europe’s seas’, EEA Report No 14/2019, European Environment Agency (https://www.eea.europa.eu/publications/nutrient-enrichment-and-eutrophication-in) accessed 13 May 2024.
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EU, 2008, Directive 2008/56/EC of the European Parliament and of the Council of 17 June 2008 establishing a framework for community action in the field of marine environmental policy (Marine Strategy Framework Directive, MSFD) (OJ L 164, 25.6.2008).
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Nutrients in Europe's transitional, coastal and marine waters (Indicator)

Number of time series available showing trends in dissolved inorganic nitrogen and orthophosphate concentrations for each regional sea during the period 1980-2021

Zero Pollution Action Plan 2030 target or policy objectives

Other relevant indicators and signals

References and footnotes