Algal growth is accelerating in lakes across Canada, including those far from human development, and a new study shows that climate change is the primary driver. A research team led by scientists at McGill University and Université Laval examined lake sediment cores from 80 lakes across Canada to uncover long-term changes in algae levels. The study, published in Communications Earth & Environment, reveals a dramatic uptick in lake algae production since the 1960s. “Over the past 150 years, we’ve seen algae levels rise in most Canadian lakes, but in the 1960s, algae levels accelerated dramatically, increasing at a rate seven times faster than before,” said Irene Gregory-Eaves, co-author and biology professor at McGill. “What was most surprising is that this happened even in remote lakes, far from any immediate sources of human pollution or development.” To identify the cause of these changes, the team combined the study of natural archives – lake sediment cores that date back to the 1800s – with machine learning techniques to detect long-term trends. They then compared those algae records with historical data on air temperature, solar radiation, and nearby human activity. “Our research points clearly to climate change as the primary driver of the algae dynamics,” said Dermot Antoniades, co-author and limnology professor at Université Laval. “As climates warm, lakes are getting warmer too, which create ideal conditions for algal growth.” Other factors, such as solar radiation and land use, played a role, but warming was the strongest influence. Previous studies looked at few lakes or shorter time spans, often linking algae growth to local pollution such as fertilizer run-off. “Our research shows something larger: climate change, specifically rising temperatures, is the main driver – even in remote lakes with no nearby human activity,” said Hamid Ghanbari, lead author of the study and a postdoctoral researcher at Université Laval, who was co-supervised by Antoniades and Gregory-Eaves. An ‘all-hands-on-deck' issue This is an issue everyone should be aware of, the researchers say. “Lakes are places where we swim, fish, drink water, and run businesses,” said Antoniades. “When algae grow uncontrollably, it can harm our health, kill fish, stink up beaches, and cost money.” The findings point to a need for coordinated action on a global scale. “Our study shows that local fixes alone, such as reducing fertilizer runoff, aren’t enough anymore. Climate action is essential for protecting lakes in the long run,” Ghanbari said. “Healthy lakes mean healthy communities,” Ghanbari said. “Ignoring these issues result in greater risks to our water, wildlife, and wallets. This is an ‘all hands on deck’ issue that requires the participation and commitment of individuals and governments, NGOs and businesses to reduce our carbon footprint.” About the study Widespread 20th-century increases in Canadian lake primary production and the roles of climate warming, solar irradiance and human impacts by Hamid Ghanbari, Irene Gregory-Eaves, Dermot Antoniades and colleagues from UQAM, Université de Sherbrooke, Queen’s University and the NSERC Lake Pulse network was published in Communications Earth & Environment. This research was funded primarily by an FRQNT Team grant and the Natural Sciences and Engineering Research Council of Canada (NSERC), Canadian Lake Pulse Network.