Phosphorus in Georgian Bay. Out of whack?

Phosphorus is a necessary nutrient for aquatic life. The natural balance in Georgian Bay can get harmfully thrown out of whack on the high and low side with human interference.

We add risk to our near-shore water by contributing too much phosphorus in wastewater and fertilizer run off among other sources, that is further exacerbated by intense rainfall from climate change. Too much phosphorus under the right conditions can lead to the formation of algal blooms, some of which can be toxic. Conversely, there is a threat of too little phosphorus in the deep open waters threatening the food web. For example, there has been a collapse of diporeia, a miniscule freshwater shrimp that was once the most abundant benthic organism in the offshore deep parts of Lake Huron and Georgian Bay that coincided with the timing of active filter feeding by invasive mussels. The lack of phosphorus in the outer waters is possibly linked to these invasive mussels (zebra and quagga), which we brought to the Great Lakes in the ballasts of ships and through other human pathways.

Testing water Georgian Bay

A report called the "State of the Bay 2018" looks at total phosphorus in eastern and northern Georgian Bay as an important water quality measurement, and it is the first issue to be addressed among key issues confronting the Bay. The report was compiled by the Georgian Bay Biosphere Reserve (GBBR) with support from a steering team that included Georgian Bay Forever. It indicates that the trend for total phosphorus is deteriorating, meaning it is showing change away from acceptable conditions.

Below are links to more information on total phosphorus and how it is impacting the Eastern and Northern Georgian Bay. Hover and click on these topic links to learn more:

Phosphorus Levels in Outer Georgian Bay are Going Down

By David Bywater. David Bywater is the State of the Bay Project Manager for the Georgian Bay Biosphere Reserve, a not-for-profit dedicated to environmental and community well-being. He can be reached at To find the full State of the Bay Report, please visit

Think about what makes life possible underwater. Phosphorus is the “food” that microscopic plants and animals need to survive. As the foundation of our food web in Georgian Bay, phosphorus is an important nutrient for us to measure when we study the health of our ecosystem. You can imagine that there wouldn’t be many fish or loons without healthy nutrient levels supporting the rest of the food web!

Phosphorus levels affect algae growth and water clarity, in turn affecting swimming, boating, fishing and aesthetic enjoyment. Without clean and safe water, many of our favourite summer activities are at risk. Too much phosphorus is not a good thing – but neither is having too little.

Georgian Bay receives nutrients that are brought through the watershed from many rivers. Organic materials and nutrients from land travel into lakes with spring runoff, raising the phosphorus levels early in the year. In shallower, protected bays or near wetlands, phosphorus levels can be much higher, which is good for fish habitat. This type of nutrient-rich habitat is considered more productive, supporting more species of algae and phytoplankton, as well as a more diverse food web.

When nutrients are trapped or concentrated in warmer, shallow waters (such as in late summer) an algal bloom may result. These algal blooms make water less attractive for boating and swimming, and if you draw lake water for drinking, it will taste and smell foul. Algal blooms can also produce cyanobacteria, or blue-green algae, which can create toxins dangerous to both wildlife and humans.

Since the 1970s, people in Ontario have made efforts to reduce phosphorus loads to surface water. Nutrients from sewage-treatment plants have been greatly reduced, and there is less phosphorus pollution, from agriculture and stormwater. They still remain but are much lower than they were in the past.

In the offshore, deep waters of Georgian Bay, phosphorus levels have been naturally low, but for the first time in recorded history, concentrations are now as low as those of Lake Superior. The low level of phosphorus represents an unprecedented low level of nutrients—critical in the open-water system for a healthy food web and stable fish community.

Why has this occurred? The answer is probably very complex. The invasion and rapid spread of zebra and quagga mussels has resulted in the loss of phytoplankton and zooplankton from the lake due to the mussels’ immense capacity to filter lake water. Their feeding seems to have used up most of the nutrients in Georgian Bay, and this is having a destabilizing effect on the aquatic ecosystem. Most likely, several factors are interacting, and more research will be required to understand this phenomenon.

We still need people to reduce their phosphorus pollution. The slow movement in nearshore waters means that an increase in nutrients along the shore will not benefit the offshore deep water but will accumulate, creating nuisance algal blooms—sometimes toxic ones. So be sure to:

  • Keep a buffer of vegetation along shorelines, which reduces nearshore nutrients.
  • Lower your household phosphorus pollution by avoiding detergents and soaps.
  • Maintain your septic system properly to avoid leaks and nutrient spills into water.
  • Volunteer to monitor water quality by visiting

Water esting collage Georgian Bay

To find the full State of the Bay Report, please visit

Georgian Bay Forever, Water Quality and Phosphorus

Georgian Bay Forever has a history of supporting novel research and finding contemporary solutions to help improve water quality monitoring by working with academic institutions, like-minded-partners, and municipalities. Building on our previous water quality work and collaborations in standardizing protocols, GBF is focused to improving the efficiency of water quality monitoring and evaluating the impacts of net pen aquaculture to ensure sustainable policy.

To learn more about these projects and how you can support them, please review these summaries and links to more information:

AUV tool for water quality testing

  • Revolutionizing water quality measurement with Canada's first autonomous underwater vehicle. Georgian Bay Forever is excited at the prospect of purchasing the first Canadian Autonomous Underwater Vehicle (AUV) which would drastically improve water quality data measurement. We need your help to get it! Through this machine, we are hoping to create high resolution data maps of the watersheds and a number of chemical and physical parameters. This would include measuring the amount of chlorophyll, turbidity and biomass of plants. Increases in these factors can be indicators of excess loads of phosphorus. Additionally, this device will allow the creation of Digital Elevation Models (DEM) for Canadian waters; a digital representation of the watershed…allowing predictions to be made to model the impacts of climate change, water levels, development, spills, sewage outflows, septic failures, bacterial contamination or conservation measures. Learn more here.

  • Assessing the impact of net pen aquaculture in Georgian Bay. Past research that was compiled for GBF has shown that among other risks, nutrient loading from phosphorus either in the form of food or waste from this type of fish farming could deteriorate water quality (and has done so in sites like Lake Wolsey as revealed by the Georgian Bay Association in their Spring 2018 newsletter). Industry has taken steps to alleviate some of these concerns, but no evaluations have occurred since the changes and rules are shortly to be set for expansion of this industry. GBF is engaged in providing scientific information about what kind of sites and practices do not harm water quality and aquatic ecosystems. To learn more about the research in Georgian Bay by the University of Guelph that Georgian Bay Forever is funding, please visit this link.
  • Our past work related to phosphorus and water quality includes:

    • Standardizing Protocols. Georgian Bay Forever (GBF) worked from 2011 to about 2016 to standardize water quality measurements with partners in Eastern Georgian Bay including the Georgian Bay Biosphere Reserve and Severn Sound Environmental Association. For the Township of Georgian Bay, GBF prepared a report that analyzed water quality monitoring in the area and recommended plans for going forward. Within the report is a discussion an Assessment of cyanobacteria dominance in embayments along the Georgian Bay Coastline. Summarized findings showed that “favourable conditions for cyanobacterial growth already exist in these oligotrophic [low nutrient] embayments and mean [average] epilimnetic [above the thermocline and metalimnetic [transition zone in the themocline] total phosphorus concentrations need only rise, say 50% to mesotrophic [moderate nutrient] levels of 12 - 15 μg/L (similar to Sturgeon Bay) from current levels of 8-9 μg/L to generate blooms of nuisance proportions." Given rising Great Lakes water temperatures and increased precipitation (run-off) from climate change, and the presence of iron and anoxia (favourable conditions for bloom formation), the process and responsibilities for monitoring were solidified.
    • Supporting research by the University of Toronto's Associate Professor Maria Dittrich in Honey Harbour to help her research measuring the make-up of the sediment, and its capacity to release phosphorous into the water.
    • Supporting research that challenges the focus of looking at phosphorus in isolation as a cause in cyanobacteria bloom formation, and reveals the critical role of anoxia and ferrous iron. See the report by Molot and others, York University.

    Severn Sound Environmental Association and Phosphorus Monitoring

    Phosphorous has been monitored in Severn Sound since 1969. The sound was formerly listed as a Great Lakes Area of Concern, as the 1970s and 1980s marked a period of high nutrient loading from sources including wastewater-treatment plants, private septic systems and agricultural and stormwater runoff. Severn Sound was considered eutrophic (nutrient-rich) at that time and experienced excessive algae growth, particularly in Penetanguishene Harbour.

    Severn Phosphorus concentrations

    A combination of remedial actions, such as controlling runoff from farms, as well as stewardship activities, septic upgrades and water-treatment upgrades, combined with ecological changes (such as the introduction of zebra/quagga mussels) have led to significant reductions in total phosphorus and algae growth. The Remedial Action Plan (RAP) targets for total phosphorus of 20 µg/L for Penetanguishene Harbour and 15 µg/L for the rest of Severn Sound continue to be met.

    There have been no significant trends in total phosphorus since the mid-1990s, except for a decrease in the inner Penetanguishene Harbour. Although Severn Sound is now considered lower in nutrients, it is important to continue with remedial actions and monitoring, as climate change and invasive species continue to affect water quality in often-unpredictable ways.

    Severn Phosphorus concentrations

    What you can do, from the LAMP

    The LAMP is the Lake Huron Lakewide Action and Management Plan, 2017-2021. Its purpose is " In keeping with the Great Lakes Water Quality Agreement (the Agreement), the governments of Canada and the United States have committed to restore and maintain the chemical, physical, and biological integrity of the waters of the Great Lakes. This 2017-2021 Lake Huron Lakewide Action and Management Plan (LAMP) fulfills a United States and Canadian commitment of the Agreement to assess ecosystem condition, identify environmental threats, set priorities for research and monitoring, and identify further actions to be taken by governments and the public that address the key threats to the waters of Lake Huron and the St. Marys River"--Executive summary, p. viii.

    For the full report, please go to this link, and download the report. Below is a list of of what you can do taken from page 52 of the report:

    Landowners and the public are encouraged to do their part to prevent nutrient and bacterial pollutants from entering groundwater, streams, lakes, wetlands, and Lake Huron by undertaking the following actions:
    • Choose phosphate-free detergents, soaps, and cleaners - use appropriate amounts;
    • Avoid using lawn fertilizers;
    • Always pick up pet waste;
    • Use natural processes to manage stormwater runoff and reduce the amount of impervious surfaces;
    • Install a rain barrel and plant a rain garden with native plants, shrubs, and trees so that water soaks into the ground;
    • Inspect and pump out your septic system regularly;
    • Implement improved septic technologies, including conversion of septic systems to municipal or communal sewage systems;
    • Incorporate agricultural best management practices, such as grassed swales, filter and/or buffer strips to control and reduce store stormwater runoff; and
    • Keep cattle out of streams; leave a buffer strip to trap nutrient and sediment runoff; and plant a shelter belt.