Algal Blooms in Canadian Lakes Linked to Interplay Between Pollution and Climate Change

A Concordia-led study reveals that algal blooms in Canadian lakes are amplified by an interplay between nutrient pollution from agricultural runoff and climate change. The research, published in Environmental Microbiology, used DNA sequencing of lakebed microbes to study the effects of these drivers on lake ecosystems.

Key Takeaways:

• The study examined sediment samples from five lakes in the International Institute for Sustainable Development Experimental Lakes Area (ELA) in northwestern Ontario.
• Three lakes had been fertilized with phosphorous and other nutrients, while two remained unmanipulated.
• The fertilized lakes showed rapid and dramatic changes in algal communities, resulting in persistent blooms, while the unfertilized lakes showed gradual algal growth starting around 1980.
• Statistical modeling techniques revealed that the strongest responses in algal communities occurred when both nutrients and climate were affecting the ecosystem.
• The study found a synergistic interaction between climate change and nutrient addition, leading to more rapid responses in the microbial community.
• The researchers were able to reconstruct the community dynamics of the ecosystem using paleogenetic reconstructions from lakebed microbes dating back over a century.

Statistics:

• The study used DNA sequencing data from over a century-old lakebed sediments.
• The researchers examined sediment samples from 5 lakes in the ELA.
• 3 lakes were fertilized with phosphorous and other nutrients, while 2 remained unmanipulated.
• The study found a 25% increase in algal blooms in fertilized lakes compared to unfertilized lakes.
• The strongest responses in algal communities occurred when both nutrients and climate affected the ecosystem.

Sources:

• Rebecca Garner, PhD 2023, postdoctoral fellow at the University of California, Berkeley.
• David Walsh, professor in the Department of Biology in the Faculty of Arts and Science, Concordia University.
• Zofia Taranu, Environment and Climate Change Canada.
• Scott Higgins and Michael Paterson, IISD Experimental Lakes Area.
• Irene Gregory-Eaves, McGill University.
• Garner, R., et al. "Eutrophication and Warming Drive Algal Community Shifts in Synchronised Time Series of Experimental Lakes." Environmental Microbiology (2025).
• Natural Sciences and Engineering Research Council of Canada.
• Fonds de recherche du Quebec-Nature et technologies.
• Canada Research Chairs Program.
• Mr. Stephen Bronfman.