Eutrophication is the enrichment of natural waters with plant nutrients, largely derived from humankind’s activities. This disturbs the balance of aquatic life and results in poor water quality. The review explains the causes of eutrophication, the various impacts, and the legislation and initiatives that are being used to control the problem.

Revised August 2006 (First published April 2000)

This report is the second in a series of FWR Reviews of Current Knowledge (ROCKs). Each review focuses on a topical issue in the water-environment area and provides concise, readable, scientific and technical information on the subject. They are intended to facilitate a wider understanding of the issues involved and to promote informed opinion about them.

The subject of this ROCK is eutrophication, the increasing enrichment of natural waters with plant nutrients largely derived from man’s activities. The effects are the excessive growth of algae and other aquatic plants, poor water quality and serious disturbances to the balance of aquatic life. Such changes can destroy wildlife habitats and interfere with a range of water uses from recreation to the production of drinking water.

The review is largely confined to U.K. freshwater problems and their resolution within the context of European Union legislation. It is also topical. Both the Environment Agency (of England and Wales) and the Environment and Heritage Service (of Northern Ireland) have recently drafted strategies for tackling eutrophication. Recent and forthcoming EC legislation addresses the control of nutrient chemicals entering the aquatic environment, as does the current debate on sustainable agriculture.

The review explains the causes of eutrophication and how the phenomenon is categorised. The potential sources of the nutrients that lead to eutrophication are defined and quantified in general terms. The effects of nutrient sources and how a water body may respond to nutrient control measures are very site-specific. This is exemplified by reference to Lough Neagh in Northern Ireland.

Information is provided on the various impacts of eutrophication. Finally, the review provides information on a range of legislation and initiatives that will affect eutrophication. These include:-

• Strategies being developed by the Environment Agency and by the Environment and Heritage Service
• Remedial and control measures
• EC legislation (current and proposed)
• Agri-environment schemes