Phosphorus and deepwater oxygen relationships in Lake Simcoe
Ann Arbor, MI — To help restore coldwater fish populations, a new oxygen target of 7 mg/L in the deepwaters of Lake Simcoe has been identified in the Ontario government’s Lake Simcoe Protection Plan.
Lake Simcoe is the largest inland lake in Southern Ontario, Canada, next to the Great Lakes. It is a popular fishing destination, but important game fish like lake trout started declining in the 1960s because of poor deepwater oxygen conditions caused by high phosphorus loadings to the lake. This study revisited the relationships linking phosphorus loading to oxygen concentrations since the invasion of zebra mussels in the 1990s.
"Despite dreissenid invasion, there still appears to be a strong link between phosphorus loads and deepwater oxygen," says Dr. Joelle Young, the Lake Simcoe Scientist with the Ontario Ministry of the Environment. "So reductions in phosphorus loads should lead to better conditions for coldwater fish and we can use these relationships to set goals for the lake."
To reach the oxygen target of 7 mg/L, phosphorus loads need to be reduced to 44 tonnes/yr. This is a substantial reduction from the current average load of 72 tonnes/yr. A Lake Simcoe phosphorus reduction strategy has been developed by the Ontario government to meet the loading goal. The strategy is a long-term, phased approach for identifying and reducing the major sources of phosphorus entering Lake Simcoe and its watershed.
Original Publication Information
Results of this study, "A re-evaluation of the empirical relationships connecting dissolved oxygen and phosphorus loading after dreissenid mussel invasion in Lake Simcoe," are reported by Joelle D. Young, Jennifer G. Winter and Lewis Molot in the latest issue (Volume 37, Suppl. 3, pp. 7-14) of the Journal of Great Lakes Research, published by Elsevier, 2011.
Contacts
For more information about the study, contact Jennifer Winter, Ontario Ministry of the Environment, Environmental Monitoring and Reporting Branch, 125 Resources Road, Toronto, ON M9P 3V6, Canada; Jennifer.Winter@ontario.ca, (416) 327-3715.
For information on the Lake Simcoe Protection Plan go to www.ontario.ca/lakesimcoe.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, Environment Canada, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; jglr@ec.gc.ca; (306) 975-5310.
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