The acidification of lakes in Canada in recent decades, caused mostly by industrial pollution, is pushing freshwater habitat into "an entirely new ecological state," researchers say. As acid levels increase and calcium levels drop, lakes are finding themselves playing host to a proliferation of small jelly-like invertebrates.
The reduction of calcium in acidifying waters is good news for the jellies known as Holopedium, but it's bad news for traditional plankton (like Daphnia water fleas) that serve as the foundation for freshwater ecosystems.
Without enough calcium available, Daphnia aren't able to get enough sustenance or bulk up their calcium-rich exoskeletons, their main defense shield. Holopedium, on the other hand, can subsist on less calcium and are able to use their jelly-like outer coating to protect themselves from predators.
In some lakes in Ontario, researchers are able to scoop up large collections of the jellies in their hands. Swimmers emerge with the caviar-like slime balls clinging to their arms and backs. It's gross -- but its also ecologically disruptive.
"As calcium declines, the increasing concentrations of jelly in the middle of these lakes will reduce energy and nutrient transport right across the food chain, and will likely impede the withdrawal of lake water for residential, municipal and industrial uses," study co-author Andrew Tanentzap, an ecologist at the University of Cambridge, explained in a press release.
The jellies continue to multiply, with some data suggesting the population doubled between the mid-1980s and mid-2000s. Scientists worry the jellies might not just disrupt the food chain but clog filtration systems used to extract fresh drinking water.
"It may take thousands of years to return to historic lake water calcium concentrations solely from natural weathering of surrounding watersheds," Tanentzap said. "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."
The work of Tanentzap and his colleagues was published this week in the Proceedings of the Royal Society B.