Next Steps

This program is one of the most extensive monitoring efforts completed on a nearshore zone in Lake Ontario.

It has provided some useful information about the water quality and the physical lake characteristics in the Ajax and Pickering area, and how these change over time and space.

While the goals of this program were not research-focused, we hope that scientists studying issues in the Great Lakes will be able to use the monitoring data collected for their studies.

Implications of Water Quality

It is important to recognize that science and theories are constantly changing. What we learn from journals is usually from studies done years prior, as there typically is a lag between the study and publication.

As a result, it is also important to look at interviews with scientists, attend conferences to find out where the interest is, where the knowledge is, and where it is going.

A great example of this is theories on the resurgence of algae in the Great Lakes.

In the past, it was thought that everything was related to the soluble reactive phosphorus concentrations in the Great Lakes, because this is an important form of phosphorus that can be used by algae to grow.

However, if phosphorus contributions to the Great Lakes are decreasing, why do we see a resurgence of algae washing up on the shoreline? Why is there more algae some years than other years? Why are there only water quality guidelines for the open waters and not the shoreside?

These are great questions that many university and government scientists are currently researching, and the results are in different stages of completion.

Theories about why there is a resurgence of algae across the Great Lakes include:

1. The particulate phosphorus (phosphorus bound to particles or sediment) that is entering via streams, rivers, and storm drains (or being resuspended from the lake bottom) is bioavailable.

Mussels can convert this particulate phosphorus into a form that algae can use (see Return of the Slime).

2. The amount of total phosphorus entering the lake is decreasing, but perhaps the proportion of total phosphorus that is available for algae uptake is increasing.

So we might have less phosphorus entering the lake, but there is more phosphorus in the form that algae can use.

U.S. scientists have found that the ratio of soluble reactive phosphorus to total phosphorus in Lake Ontario tributaries is high (more available for uptake or bioavailable) and that the ratio at shoreside sites is lower than in the rivers, similar to embayments and different from the offshore (Mackarewicz et al., 2012).

This suggests that the bioavailable phosphorus entering the lakes is either being consumed by biota and/or being diluted in the nearshore.

3. Nutrients entering the lake during the winter and spring melt are becoming trapped in the nearshore due to the spring thermal bar, a band of water by the nearshore that has a different density than offshore waters, preventing mixing between the two zones.

The thermal bar is responsible for trapping nutrient-rich waters close to the shore. These trapped nutrients increase productivity, and productivity is happening at earlier times in the year allowing a longer growing season for the algae (see Mackarewicz et al., 2012b, Auer et al., 2004).

This means that “good” and “bad” years might be predetermined based on winter/spring loadings and the rate or time that the lake water is warming in the spring.

4. In Lake Ontario, we still see Cladophora blooms even when the average soluble reactive phosphorus concentrations are at or below the range believed to support the algae bloom. It has been suggested that the growth rate of algae is very sensitive to the phosphorus loading from local watersheds (Higgins et al., 2012).

This means that the differences we see between locations along the shores of Lake Ontario is related to an urban gradient and the different amounts of phosphorus entering from the watersheds.

In cases like this, the bioavailability of the total phosphorus (both particulate and dissolved) becomes very important. Higgins et al. (2012) suggest soluble reactive phosphorus may underestimate the availability of phosphorus since the mussels transform particulate phosphorus into forms that algae can consume.

TRCA does not have the information to figure out if any of these theories are correct, but we will continue to work with, support, and provide the data we collect to provincial and federal scientists who are working on the resurgence of algae in the Great Lakes.

Comparison to the United States Side of Lake Ontario

It is obvious from the Ajax and Pickering water quality information collected by TRCA and the work of Howell et al. (2012ab) and Makarewicz et al. (2012) that average water quality on the north shores of Lake Ontario is of better quality than on the southern shores of the Lake.

This is in part due to nutrient sources and circulation patterns in the lake.

The Niagara River is the largest individual nutrient input to Lake Ontario (Makarewicz et al., 2012c), delivering nutrients from Lake Erie. Once the nutrients from Lake Erie enter Lake Ontario, circulation patterns in Lake Ontario become very important.

Generally, the currents follow a counter-clockwise direction in Lake Ontario with a smaller clockwise current direction in the northwest (Beletsky et al., 1999).

Once the nutrients from the Niagara River enter Lake Ontario, they are transported along the southern shores due to the dominating circulation patterns in the lake. These nutrients are mixed in with the waters along the southern shores and do not affect the Canadian shorelines as they do in the U.S.

Other differences between the Canadian and American shores of Lake Ontario include the areas where elevated nutrient concentrations are observed.

On the north shores of Lake Ontario, Howell et al. (2012b) found that phosphorus levels were elevated above 10 µg/L within 1 km of the shoreline, however, Mackarewicz et al. (2012) note that phosphorus concentrations exceeded 10 µg/L as much as 4 km from the shoreline on the American side of Lake Ontario.

The differences observed have been attributed to loading, wind events, and lake physics.

Unlike the southern shores of Lake Ontario, upwellings are prevalent along the Canadian shores of the lake. These events promote the mixing of surface and bottom waters in the lake.

However, on the American side of the lake stream loading, wind events and a prevailing water current along the south shore are thought to transport the nutrients along the nearshore without upwelling events to mix some of the nutrients with the bottom waters.

What’s Next?

In our next steps, TRCA will aim to:

  • Publish in the scientific community where results and methods are peer reviewed.
  • Present findings at scientific conferences.
  • Continue the ongoing collaboration with Environment and Climate Change Canada (lake modeling and nutrient sources and patterns in the lake).
  • Share the data collected from this program with scientists, the York Region, Durham Region, and others.
  • Make water quality information available to decision makers.
  • Create a legacy for future studies and water quality comparisons in the Ajax and Pickering area.
  • Incorporate the recent data into the study.
  • Continue collaborations with academics to work on loading and stormwater contributions to the lake, and drivers of Cladophora growth.

There is a lag time between data collection and data availability for the climatic (e.g. wind, solar, precipitation, discharge, etc) and physical (e.g. temperature and current) data used.

As this data becomes available, along with the updated water quality data, results will be incorporated into the current findings.