Eutrophication is the result of excessive enrichment of water with nutrients which may cause an increase in the accelerated growth of algae in the water column and higher forms of plants living on the bottom of the sea. This may result in a range of undesirable disturbances in the marine ecosystem, including a shift in the composition of the flora and fauna which affects habitats and biodiversity, and the depletion of oxygen, causing death of fish and other species.

Human activities resulting in anthropogenic nutrient enrichment encompass inputs from point sources (e.g. sewage plants or industry) and inputs from diffuse sources (e.g. agriculture, households not connected to sewerage, overflows, and atmospheric inputs).

The OSPAR Eutrophication Strategy sets the objective to combat eutrophication in the OSPAR maritime area, in order to achieve and maintain a healthy marine environment where anthropogenic eutrophication does not occur. The Strategy builds on long-standing commitments from Contracting Parties under OSPAR measures to achieve a substantial reduction at source in inputs of phosphorus and nitrogen into areas where these inputs are likely to cause pollution. Progress in reducing nutrient inputs is regularly assessed by OSPAR based on national implementation reporting by Contracting Parties. The eutrophication related work is implemented by OSPAR’s Hazardous Substances and Eutrophication Committee (HASEC).

To assist Contracting Parties in identifying areas in a consistent way where nutrient inputs may cause pollution, and to periodically assess the eutrophication status of the OSPAR maritime area and progress made towards the Strategy’s objective, OSPAR developed a common assessment framework: the Common Procedure for the Identification of the Eutrophication Status of the OSPAR Maritime Area.

OSPAR’s assessment work is supported by monitoring under the Eutrophication Monitoring Programme as part of the OSPAR Co-ordinated Environmental Monitoring Programme (CEMP), and by monitoring to estimate waterborne and atmospheric inputs of nutrients to the OSPAR maritime area under the RID Study and the CAMP monitoring programme. Monitoring is complemented by modelling activities on nutrient reduction scenarios and transboundary nutrient transport to help directing future actions in combating eutrophication.

The implementation of the Eutrophication Strategy takes place within the framework of the obligations and commitments of the various Contracting Parties under other international agreements. This includes the implementation of European Community legislation to reduce nutrient discharges and emissions, including for example the Nitrates Directive (91/676/EEC), Urban Waste Water Treatment Directive (91/271/EEC), the Water Framework Directive (2000/60/EEC) and the Marine Strategy Framework Directive (2008/56/EC).

For each chemical for priority action, OSPAR has developed a monitoring strategy that sets out the best way to collect data and information on sources, pathways, concentrations and effects, in order to track progress towards OSPAR's objectives for hazardous substances in periodic assessments. This includes long-term data collection under the OSPAR monitoring programmes for:

  • atmospheric inputs (Comprehensive Atmospheric Monitoring Programme - CAMP)
  • riverine inputs and direct discharges (Comprehensive Study on Riverine Inputs and Directive Discharges - RID)
  • concentrations and effects in the marine environment (Coordinated Environmental Monitoring programme - CEMP)

IA2017 Eutrophication status in areas assessed in Arctic Waters, the Greater North Sea, Celtic Seas, and the Bay of Biscay, 2006–2014:

Data available here: