Phosphorus in aquatic ecosystems: chapter 4

Conclusion

Overall, there are areas in Canada where total phosphorus concentrations were found to be high - nearly one-third of sites assessed were classified as eutrophic or hyper-eutrophic. Of these 21 sites, 10 had TDP levels of less than 25% of the TP, indicating that the majority of phosphorus at these sites was in suspended sediment. However, 5 sites categorized within these upper trophic categories had a high amount of bioavailable P. Four of these sites were in the Prairies, and one in southern BC.

For TP, 16 of 75 sites (21%) had increases between 1990 and 2006, while 14 of 39 (36%) had increases in TDP, the form that is readily available for take up by plants. Only 2 out of 39 sites, with both TP and TDP showed opposite trends - the remaining sites had consistent results between the phosphorus fractions.

For some sites the magnitude of the change measured may be of concern as it was great enough to increase the trophic status of the aquatic ecosystem.

It is important to note that the monitoring sites included in this assessment do not cover all areas where excess nutrients are a problem (e.g. Lake Winnipeg) but only those for which sufficient data were available from Environment Canada’s water quality networks.

Further work to better understand what is driving the trends and the levels of phosphorus across Canada is underway including the potential impacts to aquatic ecosystems, particularly for those watersheds which exhibit the highest magnitude of change.

Documentation

Bricker S., B. Longstaff, W. Dennison, A. Jones, K. Boicourt, C. Wicks, and J. Woerner, 2007. Effects of Nutrient Enrichment in the Nation's Estuaries: A Decade of Change. NOAA Coastal Ocean Program Decision Analysis Series, No. 26. National Centers for Coastal Ocean Science, Silver Spring, MD. 322 pp.

Environnement Canada. 2009. Canadian Environmental Sustainability Indicators - Annual Report. Ottawa. ON. Accessed on June 21, 2010. www.ec.gc.ca/indicateurs-indicators.