Highlights

  • This report summarizes monitoring and research by the Ministry of the Environment, Conservation and Parks, Ministry of Natural Resources, Lake Simcoe Region Conservation Authority, Public Health Units and academic partners up to 2022.
  • Land use and natural features in the Lake Simcoe watershed have continued to change. Agricultural land has declined and urban land use has increased, while woodlands and wetlands saw gradual losses. Baseline data for high-quality natural cover on the watershed have been established, and, if tracked over time, could help maintain, protect and enhance natural cover.
  • Invasive species continue to be a significant threat to Lake Simcoe and its watershed. All of the species on the 2014 Lake Simcoe watch list (except those regulated federally) are now regulated under Ontario’s Invasive Species Act. Two of these species — oak wilt and water soldier — were recently detected within the watershed. Coordinated efforts have begun to monitor and manage these two invaders. Additionally, previously established aquatic invaders, quagga mussels in particular, have likely changed how the lake functions, altering nutrient cycling and aquatic habitat with changes occurring throughout the food web.
  • Climate change continues to be a key stressor. Annual air temperatures have risen by 1.9°C since 1980, leading to shorter ice cover duration, warmer lake temperatures and shifts in seasonal water temperature patterns. These changes can affect nutrient and dissolved oxygen dynamics, and the seasonal processes of plants and animals, such as delaying spawning of coldwater fish.
  • Water quality of Lake Simcoe and its tributaries has changed over time. There have been improvements in the lake such as increasing deepwater oxygen levels and decreasing phosphorus levels. While emerging contaminants like microplastics and PFAS have been detected, they are below guideline levels. Fish contaminant levels have generally declined. Chloride levels, however, have risen, with some streams exceeding guidelines to protect aquatic life.
  • The aquatic life in Lake Simcoe and its tributaries have been altered due to changes in climate, water quality, urban land use and the addition of invasive species. The abundance of aquatic plants around Lake Simcoe’s shoreline has increased, primarily due to invasive plants. The community on the lake bottom is now dominated by invasive mussels. In open water, the amount of algae and zooplankton has declined. While abundances of many fish populations have remained relatively stable, coldwater fish like wild and stocked lake trout and stocked lake whitefish have declined.
  • Lake Simcoe is a changing lake that is no longer functioning as previously understood. Largely driven by changes in the climate and invasive species, there have been dramatic changes in the delivery to and cycling of phosphorus in the lake. With significant changes in recent decades to Lake Simcoe and its ecosystem, continued monitoring and research, adaptive management, and sustained collaboration are essential to protect the lake for generations to come.