'Jellified' lakes coming to Canada

Lakes in the Canadian Shield are slowly becoming “jellified,” a legacy of acid rain that changed the water chemistry and has made life easier for a tiny crustacean with a big jelly blob on its back.

In the granite hills of Algonquin Park and the Gatineaus, lakes are low in calcium to start with.

The acid rain years washed away much of the calcium in the lakes and surrounding soil, says biologist John Smol of Queen’s University.

And this tips the balance away from a little crustacean that normally lives in this lakes, called Daphnia, and lets another one called Holopedium take its place.

Holopedium needs less calcium. Both animals are sometimes called water fleas.

“This we think is quite major,” Smol said. “It’s a legacy of acid rain. This was a very slow problem, really under the radar.”

Holopedium carries a bulbous coating of jelly, possibly a defence against predators.

The ecological problem is that Daphnia is an important part of the food web in lakes. But a lot of water species can’t eat the bigger jelly-coated flea.

It’s also unpleasant for some people who just want to enjoy the lakes: Clusters of fleas can wash up on shore (Smol calls them “goo balls”), and then there’s the way they feel.

“People say when they swim through it  feels like little bath beads,” he said.

Another problem is that they can clog water intakes.

Lakes in the Rideau system have fairly high levels of calcium and are so far safe from the change. The lakes being threatened are the ones on granite, which were most harmed by acid rain.

The study is published Wednesday in a science journal called Proceedings of the Royal Society B.

“These are Precambrian Shield lakes, so large parts of Ontario, large parts of Quebec, Nova Scotia,” as well as the Adirondacks and Washington State are involved, he said.

The increase comes partly from looking at government records of lakes, but also by looking at the “little bits and pieces of the exoskeletons,” the hard outer material from the water fleas’ bodies that can be traced back to sediments from the 1800s.

There isn’t much we can do, Smol said.

“The good news is that we are able to identify one of the effects of reduced lakewater calcium levels. The bad news is that many lakes have passed critical thresholds, and we have been reduced to the role of a spectator as these changes continue to unfold. Once again we see that there are many unexpected consequences of our actions — and they are mostly negative.”

Funding came from the Natural Sciences and Engineering Research Council and Ontario’s Environment Ministry.

Original Article
Source: ottawacitizen.com/
Author: Tom Spears