A combination of industrial pollution and climate-change-driven oxygen loss is turning the great Canadian lakes into jelly, according to new research by Cambridge University scientists published in Proceedings of the Royal Society B.
A "battle of the plankton" between two competing species, Holopedium and the planktonic Daphnia, has been taking place in the delicate ecosystem of the lakes; however, calcium depletion in the lakes is making survival difficult for Daphnia, which require the mineral to form a vital component of their exoskeleton defending them from predators, and consequently populations of Holopedium have doubled since the 1980s. Without the presence of Daphnia, algae is multiplying and providing an unlimited food source for its competitor.
The study suggests that poor Daphnia have also been compromised by climate change, which is causing depletion of oxygen in the lakes and leading to increasing populations of “larval midges – the main predator of Daphnia.”
“Lakes across eastern Canada have seen Holopedium populations explode in the last thirty years; particularly in lakes in the province of Ontario that have seen a recent Eurasian invasion of the spiny water flea – which also favours hunting Daphnia, affording Holopedium even more room in these ecosystems to expand,” Cambridge said in a press release.
The" jellification" observed by the researchers is being caused as a result of Holopedium’s outer coat, which is made of a jelly-like substance, and scientists are very worried that the rapidly solidifying lakes could impact on local supplies of drinking water by clogging filters. In Ontario, around twenty per cent of drinking water comes from lakes with depleted calcium concentrations.
As the jelly expands throughout the lakes, it is also choking other essential nutrients out of the food chain, and could potentially reduce the water to an almost lifeless sludge.
“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,” said study co-author Dr Andrew Tanentzap, from the University of Cambridge’s Department of Plant Sciences.
Tanentzap explained that acid rain generated by increased industrialization had depleted calcium from the soils surrounding the lakes.
“Pollution control may have stopped acid deposits in the landscape, but it’s only now that we are discovering the damage wasn’t entirely reversed,” he warned. “It may take thousands of years to return to historic lake water calcium concentrations solely from natural weathering of surrounding watersheds.
“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 many have pushed these lakes into an entirely new ecological state.”