These freshwater algae samples were taken by Michigan Technological University students. Shown is algal scum. (Photo by Jason Oyadomari)

MARQUETTE — Rising temperatures and changing environmental conditions in the Great Lakes are contributing to harmful algal blooms, and new research suggests that the nearshore regions of Lake Superior could indicate climate change’s effects on the region’s ecosystem.

The study, in the Journal of Great Lakes Research, collected samples from 10 nearshore stations along the Canadian shoreline throughout spring, summer and fall.

Across all seasons and sampling locations, researchers from York University and the Ontario Ministry of the Environment identified 23 species cyanobacteria at non-bloom levels.

Cyanobacteria, also known as blue-green algae, are a type of bacteria found in freshwater that can grow rapidly and produce toxins that harm wildlife and humans.

Although important to a variety of organisms, excessive growth of this bacteria can lead to blooms that impede recreation and deplete oxygen in the water.

The blooms are often associated with warm, nutrient-rich lakes, but recently have been showing up in cold, low-nutrient lakes such as Superior, said Krill Shchapov, the lead researcher on the study and a freshwater ecologist now at the Cawthron Institute in New Zealand.

“Lake Superior is warming much faster than the other Great Lakes,” said Shchapov. “But it is also in an area far from large human populations.”

The lake’s north shore is a pristine area with a majority of untouched land, which made the discovery of this bacteria all the more interesting, said Shchapov.

However, agricultural runoff, less ice cover in the wintertime and strong storms that deposit nutrients into the lake are all possible reasons for a surge in the blooms.

Because cyanobacterial blooms in warmer lakes such as Erie and Michigan are more common due to a larger human population around nearshore locations, the data on cyanobacteria there is not surprising.

However, because Lake Superior is a cold, low-nutrient lake with less land development, finding blooms in nearshore locations tells scientists how quickly climate change is impacting the lake.

According to Michigan Sea Grant in Ann Arbor, the study did not identify any blooms in Lake Superior but cited reports that confirmed four blooms in bays along the lake between 2019 and 2023. Those bays were not sampled in the new study.

Evidence of climate change in such areas highlights the extent of its impact on the environment, said Sapna Sharma, a professor of biology at York University who supervised the funding and execution of the study.

“I think about climate change a lot in this situation because this is a colder area where there aren’t that many people,” said Sharma. “It speaks to the fact that more nutrients are getting into the lake, but also Lake Superior, in particular is warming.”

Sharma said that increases in blooms, especially in pristine areas in the middle of nowhere, warrant more intense and frequent monitoring in areas with closer human populations.

According to the Environmental Protection Agency, cyanobacterial blooms can deplete the oxygen in water, making it unsustainable for fish populations, but can also produce toxic byproducts known as cyanotoxins.

When people and animals ingest these, they can cause negative health effects ranging from headaches and skin irritation to life-threatening liver and kidney damage and even cancer.

Shchapov said that while the researchers who did the study didn’t test for toxicity, 90% of the cyanobacteria found has the potential to become toxic, although Elizabeth Striano, the communications program lead for Michigan Sea Grant said it is “highly unlikely” that the cyanobacteria is toxic and dangerous.

Frequent monitoring and more research can help combat and prevent them from harming the environment and the people who live around the Great Lakes, according to Shchapov said.

Georgia Hill reports for Great Lakes Echo.