This report addresses pollution of aquatic ecosystems that originate from multiple unidentified sources or non point sources. Non point sources of phosphorus and nitrogen are of concern as they cause eutrophication or excessive enrichment of surface waters. Effects and remediation strategies are discussed. Non point sources, such as agricultural, urban and atmospheric ones are discussed. Management techniques to reduce excess nutrient transport across landscapes and into bodies of water are explained. The report discusses the need to establish controversial Thresholds of unacceptable soil contamination. Issues in Ecology is an ongoing series of reports designed to present major ecological issues in an easy-to-read manner. This Issue summarizes the consensus of a panel of scientific experts based on the information that was current and available at the time of its publication in 1998.