Limnologists are scientists who study the physical, chemical, and biological properties of lakes, rivers, and streams. They study abiotic characteristics, such as stratification and water chemistry, as well as biotic elements, such as aquatic vegetation, algae, microbes, and invertebrates. Limnologists and their work play a vital role in protecting freshwater resources, and Canadian researchers are global leaders in the field.

At a Glance

Imagine you are at the helm of a small boat, bobbing on the waves of a large lake, about 50 metres from shore. You are a limnologist and you have spent the last few hours gathering water samples from different spots in the lake as part of an environmental assessment. You are here because a large petrochemical company wants to build a refinery on the lakeshore, but before construction can be approved, an environmental assessment must be carried out to determine the potential effects of the refinery on the surrounding environment. As an expert in aquatic ecosystems, you have joined the assessment team to investigate the impact the refinery could have on the lake's health.


As a limnologist, you have been part of many environmental assessments that looked at the impact of industry on lakes and streams. Aquatic biota are sensitive to changes in their environment, making your assessment a critical component of the environmental review.

You begin by gathering baseline data to give you a better picture of the current status of the lake’s biotic and abiotic characteristics. You use a temperature probe to measure water temperature at different depths. Temperature changes with depth in lakes, which produces stratified layers that affect the amount of oxygen and nutrients available, influencing where biota can live. You then link physical characteristics to water chemistry, which will be determined from laboratory analysis of the water samples you’ve collected. You also gather data on the aquatic communities, including fish, algae, plants, and zooplankton. You can use this information on species richness and abundance to construct a food web to predict the potential impact of an industrial development, spill, or climate change scenario.

All the baseline data you gather will be used to provide a picture of the water quality of the lake before the establishment of the refinery and will be included in the environmental assessment. From the environmental assessment it will be decided if the refinery project should go ahead and what the petrochemical company needs to do to ensure that the refinery's impacts are minimized.