High loads but happy fish
Latest Phosphorus Loads Report indicates more work needs to be done, but it’s not all bad news!
Lake Simcoe watershed, ON, January 20, 2020 - While the latest phosphorus loads report shows higher phosphorus loads than expected, the news isn’t all bad. Dissolved oxygen levels continue to trend upward, which is good for a healthy coldwater fishery.
“Targets set out in the Lake Simcoe Protection Plan identified an annual phosphorus load target of 44 tonnes, but that number was aspirational,” said Mike Walters, CAO of the Lake Simcoe Region Conservation Authority.
“Forty-four tonnes was chosen because it was understood to be the phosphorus load necessary to achieve another, more critical target of 7 mg/L dissolved oxygen levels. What we’ve learned is that despite higher phosphorus loads measured, we’ve actually surpassed the dissolved oxygen target. Oxygen is the more important measure because we know how dependent fish are on cold, clean, oxygen-rich water.”
In the early 1980s, end of summer dissolved oxygen concentrations averaged 3.3 mg/L. We’ve been seeing encouraging improvements, with concentrations averaging 6.2 mg/L between 2013 – 2017, and two years (2005 and 2014) above the 7 mg/L target.
- Phosphorus loads will be higher in wetter years. More rain and snow means more flow into the rivers and ultimately the Lake. We believe the high loads in 2017* are partially a result of the wetter than average year. In fact, we know that 20% of the phosphorus loads into Lake Simcoe were the result of just two extreme weather events that year.
- Dissolved oxygen levels show a positive trend upward toward 7 mg/L, which is good for our fishery. This is despite years that had higher than anticipated phosphorus loads.
- The Lake is a complex ecosystem. We don’t quite understand how the oxygen levels are remaining positive, but this is just further proof that we need to continue our research to understand all of the factors that work together to impact the Lake’s health.
- Climate change, road salt and invasive species are other important factors that also play a role in the Lake’s health. Focusing on just one issue (or one number, like forty-four tonnes) without considering other factors and how they interact is too simplistic an approach. Ecosystems don’t work that way.
“We applaud the Province for their commitment and support for our stringent Lake Simcoe policies and guidelines designed to help reduce phosphorus,” said Wayne Emmerson, LSRCA Chair and Chairman and CEO of the Regional Municipality of York.
“With the Province’s ongoing support through the Lake Simcoe Protection Act and Plan and renewed commitment to meeting Ontario’s climate change goals, we know that we’re continuing down the right path. We also look forward to hearing more from the federal government about its commitment to dedicate another $40 million to clean up Lake Simcoe. Access to that level of financial support will enable organizations like ours to continue the much needed research and on-the-ground projects to address phosphorus and the host of other impacts to the Lake.”
* Phosphorus loads are calculated on a hydrologic year (June 1 to May 31). As an example, the 2017 hydrologic year is June 1, 2017 to May 31, 2018.
It is the mission of the Lake Simcoe Region Conservation Authority to collaborate, protect and restore the Lake Simcoe watershed with innovative research, policy and action.
Lake Simcoe Region Conservation Authority
Phone: 905-895-1281, ext. 116
Toll Free: 1-800-465-0437
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