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Acid Rain Has Turned Canadian Lakes into a Kind of Jelly

A legacy of industrial pollution is allowing slimy ooze to thrive.

Yum! A researcher holds slimy plankton taken from a lake in Ontario. (Ron Ingram/MECC)

Swimmers who dive into a number of Canadian lakes might not emerge clean and refreshed, but dripping with globs that resemble slimy fish eggs. A legacy of industrial pollution has caused great changes in the country's water chemistry, creating a boom in tiny organisms that transform lakes into "jelly."

That's the gooey news from scientists behind a new paper in Proceedings of the Royal Society B, who say that populations of this particular organism have doubled since the 1980s in many of Ontario's lakes. The reasons involve a complex dance of species, but here's the short version: Acid rain caused by smelting operations and other human activity removed calcium from the soil in drainage areas. That depleted the calcium levels in many lakes, which has hurt a kind of plankton (Daphnia) that needs the element to build armor. Enter a competing plankton, Holopedium, which requires far less calcium to bulk up and is coated with a gel that's excellent at repelling predators.

Here's one of the pulpy guys under the microscope:

Michael Arts/Canada Centre for Inland Waters

About 20 percent of Ontario's monitored drinking systems take water from places with low-calcium content, says Andrew Tanentzap, a study coauthor at the University of Cambridge. That could become a problem as the numbers of Holopedium become ever more legion and start clogging up filtration systems. The marching masses of jelly might also damage populations of larger animals—including fish that people eatas they diminish the amount of nutrients moving up the food chain.

The transformation of Canada's lakes is repulsive, but it might be something people will have to get used to. According to the researchers:

"It may take thousands of years to return to historic lake water calcium concentrations solely from natural weathering of surrounding watersheds," said Tanentzap.

"In the meanwhile, while we've stopped acid rain and improved the pH of many of these lakes, we cannot claim complete recovery from acidification. Instead, we may have pushed these lakes into an entirely new ecological state."

Ron Ingram/Ontario Ministry of the Environment and Climate Change

About the Author

  • John Metcalfe
    John Metcalfe is CityLab’s Bay Area bureau chief, based in Oakland. His coverage focuses on climate change and the science of cities.