World's Lakes At Risk Of Continued Algal Blooms Triggered By Warm Waters

The Earth's lakes may take a devastating hit from climate change, researchers report in a new study. Rapidly warming waters in freshwater bodies, including several Great Lakes and many reservoirs, trigger harmful algae blooms that ultimately threaten freshwater supplies for local ecosystems.

A team of researchers led by Catherine O'Reilly from Illinois State University analyzed satellite temperature data and long-term ground measurements taken from a total of 235 lakes, which store half of our planet's fresh surface water supply. In doing so, researchers found these particular bodies of water experienced an average rise in temperatures amounting to 0.61 degrees Fahrenheit each decade, according to a news release. This, researchers say, is greater than the warming rate of Earth's oceans and atmosphere.

"Society depends on surface water for the vast majority of human uses," Stephanie Hampton, co-author and director of Washington State University's Center for Environmental Research, Education and Outreach in Pullman, explained in the release. "Not just for drinking water, but manufacturing, for energy production, for irrigation of our crops. Protein from freshwater fish is especially important in the developing world."

While 0.61 degrees Fahrenheit may seem like a nearly undetectable change, it's actually a very significant temperature rise that could have drastic impacts. Algal blooms, for instance, ultimately rob water of oxygen and create hypoxic zones that threaten the survival of local fish. Researchers estimate a 20 percent increase in lake algae over the next century, including a five percent increase in blooms that are toxic to fish and animals.

"'These results suggest that large changes in our lakes are not only unavoidable, but are probably already happening," O'Reilly, an associate professor of geology at Illinois State University, explained in Washington State University's news release.

What's worse is bodies of water with greater depths, situated in colder regions, have experienced the most significant rates of warming. This includes four of the five U.S, Great Lakes: Superior, Ontario, Huron and Michigan. Only Lake Erie, the shallowest and warmest of the Great Lakes, was below average, while Superior, the deepest and coldest, warmed three times faster than the global average.

"Combining the ground and satellite measurements provides the most comprehensive view of how lake temperatures are changing around the world," Simon Hook, co-author and science division manager at NASA's Jet Propulsion Laboratory in California, added in the release.

In addition to air temperature, various climate factors have contributed to this warming trend, such as northern lakes losing their ice cover earlier and less cloud cover exposing waters to more sunlight, which triggers algae growth. Such an increased rate of warming could be devastating for these lakes because fish is such an important source of food.

Researchers suggest that there is an urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes in order to mitigate the impacts of global warming. Their study was published in the journal Geophysical Research Letters and was recently presented at this year's American Geophysical Union fall meeting.

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