Algae blooms in the Great Lakes are becoming increasingly common. Although a significant portion of this can be linked to climate change, the factors contributing to the growth of cyanobacterial harmful algal blooms (cyanoHABs) are much more intricate and often influenced by the rivers that supply them.

This is why Emily Varga (BSc 2018, PhD 2024) chose to focus her research on how the Thames River affects downstream cyanoHABs. While a doctoral student at the Great Lakes Institute for Environmental Research, Dr. Varga conducted microcosm experiments in the Thames River examining differences in water quality, nutrient levels, and phytoplankton communities across seasons and light availability. While in-depth ecosystem studies completed in the Thames River are limited, they inform ecosystems beyond the Great Lakes and impact policy development for freshwater management in Ontario and beyond.

Varga found that the Thames serves as a significant source of nutrients to Lake Erie, which can contribute to the deterioration of the ecosystem and lead to algal blooms. In response to reduced light availability, she observed a decline in the diversity of phytoplankton and shifts in phytoplankton community composition.

In sites along the river, higher nutrient concentrations and lower temperatures were seen, contrasting with Lake Erie sites where lower nutrient levels and higher temperatures were found. At the river mouth on Lake St. Clair, these two bodies of water mix and create a unique environment where the higher lake temperatures meet the river’s higher nutrient levels.

While certain algae were seen to dominate at specific times of the year, the composition of harmful algal blooms was more varied than previously thought: diatoms primarily dominated in winter and spring and cyanobacteria were more prevalent in summer and fall. She found algae communities to be more diverse than expected, often made up of several different species.

Similar research to Varga’s was conducted in the Sondu River and Lake Victoria continuum in Kenya where similar cyanoHABs blooms can be found. Continued research into Lake Erie and the Thames could not only help inform policy development in the Great Lakes but also freshwater management in Africa.

The similar water quality characteristics in lakes Erie and Victoria underscores the necessity for continued study and investment in both Canadian and African-led research projects.