It’s not ugly or a parasite, responded Muskoka limnologist* Dr. Norman Yan when asked for his reaction to The Toronto Star story this week about the impact of jellification by jelly-clad zooplankton on our lakes in Muskoka and Haliburton.
Dr. Norman Yan is Chair of the Friends of the Muskoka Watershed and he says he was taken back as to how alarming jellification was made to sound when it made headlines this week (You can read “Jellification in Muskoka, Haliburton may affect fish” by clicking here).
Beauty in the eye of the scientific beholder
“I was surprised that some bloggers and journalists have called the jelly-clad Holopedium “Ugly”, and one commentator actually called it a fish “parasite”. I don’t believe any of the paper’s co-authors used these words. It is true we called the paper “Jellification…” to highlight a fairly fundamental shift from crusty to jelly-clad species as dominants in the plankton, as we move from a higher calcium (Ca), phosphorus world in our lakes to a lower calcium, lower phosphorus world, but Holopedium is quite lovely to me,” says Yan. “It was the study animal in my PhD, and given it needs 20 times less calcium, and 2 times less phosphorus than Daphnia, and survives attacks from invertebrate predators better, it was already widespread in our lakes. Arguably it is a dominant zooplankton species on the Shield. The point of the paper was that it has become more dominant over the last 20-30 years at the expense of its more Ca-needy competitors.”
Featured photo: MNR’s Laurie Wesson holds a bunch of Holopedium in hand. *What’s a limnologist? Limnology is the scientific study of the life and phenomena of fresh water, especially lakes and ponds. Yan is one of Canada’s leading limnologists.
Jellification signals biodiversity loss
There are indeed a few possible ecological concerns of the change. Yan explains:
“1) We are losing biodiversity here, as several species of Daphnia are losing out to only one Holopedium species;
2) the nutritional value of the large animal plankton is reduced, as Holopedium has a much lower mineral content than Daphnia. The implications of this should be explored, but are not yet known; and,
3) there may well be less food passed up the food chain to fish in our small lakes where invertebrate predators are actually key steps between plankton and fish, because Holopedium is pretty well protected from most invertebrate predators by its jelly coat. When it is eaten, it has lower mineral content.”
As of yet, says Yan, there is only one example of a potential direct impact on water takers: that’s in Colorado, where one water filtration plant’s sand filters are now being clogged by Holopedium and they’re spending quite a bit of money to alter their intakes to try to reduce this problem.
Holopedium growth in Muskoka
In our Muskoka lakes the absolute abundance of Holopedium has increased by an average of about two fold over the last 20 years, and the relative abundance has increased more, says Yan, while the abundance of 5 species of Daphnia has declined. There are two other, smaller species of Daphnia that need less Ca than their congeners, and they are still doing well, but this won’t last if Ca continues to fall, he says.
Still, jellification doesn’t mean the end to fish in our lakes. The thing to understand, says Yan, is that “the sky is not falling, but it’s not quite the same sky as it once was.” No doubt ongoing research and monitoring is critical to the health of our lakes. The upside to the attention raised by The Toronto Star’s article this week, says Yan is that is highlights how “research in Muskoka is alerting the world to intriguing and fundamental changes that accompany human interventions in the natural world.”
About Dr. Norman D. Yan: Dr. Yan completed his Master’s degree at the University of Toronto, his PhD at the University of Guelph and worked as a research scientist at the Ontario Ministry if the Environment for 25 years. In 2000, he joined the Biology Department of York University as a tenured faculty member, and remains a Senior Research Scholar (emeritus professor) at the university. Dr. Yan has won many national and international awards. He is one of only three Canadians to receive both the K. Patalas award for research excellence in applied limnology, and the F.H. Rigler Memorial Award for limnological research from the Society of Canadian Limnology. Dr. Yan received a Premier’s Research Excellence Award from the Ontario government and was awarded a Gledden Visiting Senior Fellowship by the University of Western Australia. Recently, Dr. Yan inducted as a Fellow to the Royal Society of Canada.
Published November 22, 4pm Article by Norah Fountain
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