Nutrient Levels in Canadian Coastal Waters
and
Development of Nutrient Standards for Coastal Waters Receiving
Agricultural Inputs
SUMMARY
The National Marine Nutrient Database recently developed by Environment Canada was analyzed to examine regional trends in the extent of nutrient over-enrichment in Canadian nearshore coastal waters, and to provide a reference basis for nutrient levels that may be used to establish initial regional guidelines and/or reference conditions for dealing with coastal systems exhibiting symptoms of nutrient over-enrichment. In addition, a case study using nearshore systems in Prince Edward Island was carried out in an attempt to establish nutrient standards based on a coastal system’s susceptibility to nutrient over-enrichment.
The analyses of the National Marine Database consisted of mapping the levels of four parameters typically used to assess nutrient over-enrichment (nitrogen, phosphorus, chlorophyll a and dissolved oxygen concentration), and basic statistical analyses to determine the degree of regional differences between these parameters. The results suggest that, although some regions of Canada exhibit evidence of nutrient over-enrichment, especially Prince Edward Island where costal watersheds are characterized by porous soils and high levels of agricultural activity, most Canadian nearshore waters do not appear to be exhibit symptoms of nutrient over-enrichment as a result of anthropogenic activities. In addition, there is some evidence that West coast nearshore waters have higher nutrient concentrations than East coast nearshore waters, but the reasons for this are not readily evident based on information currently available.
The results of the case study carried out for PEI nearshore systems illustrated that, although coastal systems having a high level of agricultural activity within their watershed are more susceptible to nutrient over-enrichment, the response to nutrient over-enrichment depends on physical characteristics of the system that determine its ability to either dilute or export nutrients entering the system. An approach was developed to establish nutrient standards for coastal systems based on their potential susceptibility to nutrient over-enrichment.