Tons per year, reported separately for N and P, for a given watershed area, and when possible aggregated on a national basis. Nutrient enrichment of coastal waters may have consequences to important economic and environmental goods and services, for example, tourism and recreation, maintenance of the fishery potential, and decline or preservation of estuarine and marine biodiversity. The importance of normal to lightly enriched freshwater discharge, if free of associated chemical contaminants, to fisheries production, is however only now being fully recognized. Such impacts are likely to be negative if uncontrolled, and if close to the point of discharge. Low to moderate releases may enhance fishery production, given that natural levels of discharges from rivers sustain marine production at moderate to high levels in estuarine and coastal waters.
Concepts are available.
Further chemical specification of the nutrients is needed. The methodology is not yet ready for immediate application in many areas. The indicator needs to be measured using the mass balance principle through a technique called Regional Mass Flux Budgeting. First, system boundaries need to be established using the watershed, or drainage basin, as its horizontal extension. Vertical boundaries in the atmosphere and ground need to be selected.