The management of nutrients and potential eutrophication in estuaries and other restricted water bodies

Conceptual models are derived to indicate the signs and symptoms inherent in nutrient changes to brackish, estuarine and coastal areas of restricted circulation. These give a structured approach to detecting adverse symptoms of hypernutrification and eutrophication at all levels of biological organisation, from effects at cellular levels to the ecosystem approach. The conceptual models illustrate the bottom-up approaches to the detection and control of potential problems and the importance of top-down responses. The bottom-up approaches incorporate mechanisms with regard to inputs, retention of nutrients, biogeochemical cycling and the primary production response. The top-down approaches include the detection of responses in high-profile components of the marine system, such as fisheries, sea mammals and wading birds and seabirds, which are often of paramount socio-economic or conservation importance. The management of the above causes and consequences, and following from the adoption by signatories to proposals given by the Paris Commission (PARCOM), can be accomplished by the derivation of Ecological Quality Objectives (EcoQO) and Ecological Quality Standards (EcoQS). These are given here as a development from the Environmental Quality Objectives and Standards (EQO/EQS) approach. Such EcoQO and EcoQS are regarded as as an aid to monitoring and management of estuaries and coastal waters. That management includes recent proposals within European legislation aimed at monitoring and managing the health and integrity of coasts and estuaries, for example the implementation of the Nitrates, Species & Habitats, and Water Framework Directives. The paper, therefore, discusses both the quality and quantity of data involved in the science required by managers and the way ahead for assessing and managing the fate and effects of nutrients. Using European and U.S. examples, the paper introduces the major challenge of how the concerns highlighted can be addressed by policy action.