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 2023 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 increasing, decreasing or no trends in dissolved inorganic nitrogen and orthophosphate concentrations for each regional sea for two time periods; Pre 2000 (1980-1999) and Post 2000 (2000-2023)

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 . 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.

Available time series show that nutrient levels (nitrogen and phosphorus) in Europe’s transitional, coastal and marine waters generally declined between 1980 and 2023. The main reason for the decline would be the abatement measures. Most time series (91–94 %) show no significant change, indicating that many areas are stable.

Decreases in dissolved inorganic nitrogen (DIN) are most evident in the Baltic and Greater North Seas, while declines in phosphorus are less widespread, with some areas – especially parts of the Baltic and Black Seas. Increases are likely to be caused by phosphorus release from oxygen-poor sediments. Because data are limited in many regions, clear trends for nitrogen or phosphorus cannot be identified in every regional sea.

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.

The primary data source for this indicator is the OceanCSI_1980 - 2023 dataset (ICES 2023), which compiles information from ICES, EMODnet, and the WISE SoE – Water Quality (WISE-6). The data handling processes—extraction, selection, aggregation, trend analysis and plotting—are performed using the R programming language.

Data flagged as bad quality (bad value, probably bad value), uncertain quality (value in excess, uncertain value, missing value), or duplicates are excluded, and the 99.9% percentile of the highest values are sorted out. The analysis considers only data from depths of less than 10 meters and during the winter months, which include January to March for stations in the Baltic Sea east of 15E and January to February for all other stations.

Average values are calculated using a combination of estimated marginal means (EMM) and arithmetic means, where the EMM were used for time series containing data from both different years and months and the arithmetic means were used for time-series with yearly observations. Initial calculations of average annual concentrations are done by location and by month-year to standardise observations across different depths and time (days, hours or even minutes in some cases). 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 increasing, decreasing or no trends in dissolved inorganic nitrogen and orthophosphate concentrations for each regional sea for two time periods; Pre 2000 (1980-1999) and Post 2000 (2000-2023)

Zero Pollution Action Plan 2030 target or policy objectives

Other relevant indicators and signals

References and footnotes