‘Jellification’ in Muskoka, Haliburton may affect fish

jbailey · November 19, 2014

Interesting article from the star.

http://www.thestar.com/news/world/2014/11/18/jellification_in_muskoka_halliburton_may_affect_fish.html

Acid rain has left Ontario with a slimy legacy: the “jellification” of lakes in Muskoka, Haliburton and probably beyond as aquatic ecosystems become increasingly dominated by a tapioca-like critter impervious to changing water chemistry.

More than a decade ago, scientists discovered a troubling trend. Calcium levels in Canadian Shield lakes were declining. All organisms need a certain amount of the element to survive, but some, like crustaceans, need more.

Freshwater biologists dubbed the phenomenon “aquatic osteoporosis” and grew increasingly worried about a type of crustacean, Daphnia, known commonly as water fleas. Daphnia are a crucial component of the freshwater food web and their calcium requirements sit well above the concentrations found in many lakes.

“Now we’re asking question: if they’re losing, who’s winning?” said John Smol, who holds the Canada Research Chair in Environmental Change at Queen’s University. “I wish we had some good news here.”

A jelly-clad, calcium-poor competitor called Holopedium is increasing in abundance in temperate Canadian lakes, a team of researchers from five Ontario universities and the Ministry of the Environment have discovered. Their research is published in Proceedings of the Royal Society B this week.

This “jellification” isn’t just ugly, the scientists say. It also has long-term consequences for fish stocks and could wreak havoc on municipal water supplies.

Many of the emissions that cause acid rain have been curbed in recent years. Since 1980, sulphur dioxide pollution in the U.S. has fallen by 75 per cent. Ph levels in lakes are responding in positive ways.

But calcium depletion “is a new kind of problem — it’s a legacy of acid rain,” said Smol, a co-author of the study.

Calcium had previously leached into lakes slowly through soil and fallen trees. But acid rain stripped out most of the readily available calcium in a few short decades, leaving little for future years. Timber harvesting also removes a source of calcium.

To compare the pre- and post-acidification eras, the scientists extracted sediment cores from the bottom of 36 south-central Ontario lakes that dot the landscape between Georgian Bay and Algonquin Park. The research team, led by Adam Jeziorski at Queen’s, Norman Yan at York University and Andrew Tanentzap at the University of Cambridge, then compared preserved exoskeletons from the bottom layer of the sediment cores, which date to before 1850, to the most recent layer.

Holopedium — whose jelly doesn’t preserve well but whose thin interior carapace does — had increased in 25 of the lakes. In 31 of them, the researchers also compared water samples collected in 1980 and in 2004-2005. Holopedium abundance increased almost in lockstep with declining calcium. The researchers examined 48 Nova Scotia lakes and found similar trends, suggesting that the problem may be consistent across all geologically similar lake regions, from New England to Scandinavia.

As Holopedium muscle out Daphnia, various fish species and other organisms may suffer, says Ryerson University’s Michael Arts, another co-author: the fat, squidgy Holopedium bounce right off fish and other predators’ mouths, and even when digested are a nutritionally poor substitute because they have low calcium and phosphorous content. Once an ecosystem tips over into being Holopedium-dominant, Arts says, the problem simply grows.

Scientists in Scandinavia have experimented with adding lime to lakes and forest to fix their chemistry, but the process is incredibly expensive and only moderately successful, said David Schindler, an aquatic ecologist at the University of Alberta who was not involved in the study but praised its design.

“Right now we don’t know how to fix it, except to turn off emissions and wait.”