NUTRIENT GUIDANCE FRAMEWORK FOR CANADIAN NEARSHORE WATERS
Introduction
Within the last few decades eutrophication of coastal marine ecosystems has become recognized as a serious global problem, particularly along coastlines of the more industrialized nations. Nutrient enrichment is considered by many to be the greatest threat to the integrity of coastal systems (NRC 1994; Pelley 1998). It is also believed that this problem will become more severe as coastal watersheds are subjected to increased urbanization and industrialization. Cultural eutrophication of marine systems dramatically increased around the world beginning in the 1950s and 60s and has been related to an estimated eight-fold increase in consumption of chemical fertilizers, as well as to increases in burning of fossil fuels, land use changes and population growth in coastal areas. During this period, the amount of nitrogen entering many of the coastal ecosystems in the northeastern U.S. has increased from 5 to 14 times above natural background values (Jaworski et al. 1997). In addition, Conley (2000) has estimated that phosphorus loading to estuaries has increased 2-6 fold. Within North America, it has been estimated that 60% of US estuaries are moderately to heavily enriched with nutrients (Bricker et al. 1999; 2003). With some exceptions, coastal marine eutrophication does not currently appear to be as severe a problem in Canada. A notable exception to this is some estuaries located in agricultural areas within Prince Edward Island and New Brunswick.
The consequences of marine eutrophication can be quite severe. In extreme cases it can lead to finfish and shellfish mortality, death of benthic organisms, loss of important nursery habitat and biodiversity, and impairment of recreational value and the resulting subsequent decrease in property values of coastal areas. As a result, the Canadian Council of Ministers of the Environment, in partnership with Environment Canada, has decided that a guidance framework be developed for managing the nutrients responsible for causing nearshore marine eutrophication.
The prevention, control and management of eutrophication require an ability to determine the trophic status and assimilation capacity of aquatic systems. Only with this information can criteria be developed to serve as guidelines for the degree of nutrient enrichment permissible before the harmful effects of eutrophication become evident in coastal environments.
The major objectives of this document are to:
- Develop a draft guidance framework that addresses nearshore marine eutrophication using a science-based approach to establish site-specific guidelines for managing nearshore marine eutrophication, and
- Carry out tow case studies to demonstrate the utility of the guidance framework with respect to the data required and how the framework may be applied to set nutrient criteria.