16.6 You can’t prevent it if you can’t see it coming.

Every time Watson boards her research vessel, she takes numerous water samples from different parts of Lake Erie and Ontario, from both surface and deeper waters. As part of this water monitoring, she analyzes the samples to compare them to what would be expected in healthy systems.

On board the vessel, she performs a chemical analysis to monitor what chemicals are present, and at what levels, and to check for quantities of phosphorus and nitrogen, the nutrients that encourage growth of algae. She also conducts a physical assessment of the sample, in which she measures the pH (most freshwater organisms require near-neutral pH levels), temperature, and cloudiness of the water (turbidity). Usually, the lower the temperature the better, since water can hold more oxygen when it’s cold. Cloudy water limits photosynthesis, can clog the gills of aquatic organisms, and decreases visibility.

When Watson sees wispy filaments and other telltale signs of algae, she tests them to determine which nutrients trigger their growth, and examines their genetic makeup, which reveals if they are toxic species. Unfortunately, since Watson began these trips in Lake Ontario in 2000, and Lake Erie in 2005, she’s found that the blooms are more likely to contain cyanobacteria than in the past, resulting in more cyanobacteria toxins in the water. Algal blooms are also more severe and occur later in the season, in areas that used to be relatively algae free.

The health of an aquatic ecosystem can also be assessed by examining what lives there. This is known as biological assessment. One approach relies on simply netting, identifying, and counting benthic macroinvertebrates such as insects and crayfish that live on the bottom of streams (the benthic zone); if the stream is unhealthy, there won’t be many organisms present that are sensitive to pollutants. The abundance and diversity of pollution-tolerant and pollution-sensitive species in the sample can be used to assess stream quality. [infographic 16.5]

Infographic: 16.5BIOLOGICAL ASSESSMENT
While one can learn about the water quality in a given location by performing physical (i.e. pH, temperature, clarity) or chemical (i.e. salinity, levels of nitrogen or phosphorus) tests, these assessments typically require some expertise and equipment. An easier “first look” at a body of water is often a biological assessment—simply collecting a net sample of aquatic organisms to see what is living in the water. If there is good diversity and abundance of aquatic life, especially of those organisms that are sensitive to pollution, then it is reasonable to conclude the water is clean. A poor sampling suggests there is a problem, prompting one to look more closely at water quality to determine the reason for the problem.

Long-term chemical and biological monitoring of lakes and streams is important if we want to be able to detect and predict changes in water quality and ecosystem health. The Experimental Lakes Area (ELA) is an internationally recognized whole-lake research facility in northwestern Ontario, where long-term monitoring of eutrophication has been done since 1969. This kind of research and monitoring is essential to understanding how lakes respond to key pollutants.