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Shelley Arnott

Hope in Diversity: Environmental Change in Lakes

[Shelley Arnott by the lake]
Photo by Garrett Elliott

When Shelley Arnott (Biology) stands beside a lake, it gives her a relaxed “ahhhh” feeling. She sees recreation, tranquility and solitude. However, she also sees environmental problems and unanswered questions.

Arnott and her graduate students are working together to answer how lakes are affected by a slew of environmental stresses, including climate change, eutrophication, invasive species, declining calcium, road salt deposition, and pollution. These are big picture questions, moving target questions, that touch on physics, chemistry and biology. But for Arnott, understanding is crucial because “we need fresh water, we need it to survive. And as Canadians, it is part of who we are, part of our culture, part of our psyche.”

Like the lakes she studies, Arnott’s research methods are diverse, though conducting experiments that tease apart complex interactions are a key strength of her work. She focuses on zooplankton – tiny, free-living animals that are critical to lake ecosystems because they graze on algae and supply food for fish and other animals.

We need fresh water, we need it to survive. And as Canadians, it is part of who we are, part of our culture, part of our psyche.

In a typical experiment, large bags, 1m in diameter, are placed in an Ontario lake, and filled with water and zooplankton. The bags keep the communities of organisms inside separate from the rest of the lake, and from each other, while still exposing them to natural conditions. By altering the conditions inside the bags, Arnott and her students can detect how the zooplankton are affected over time.

In one such experiment, the amount of calcium in the water was systematically varied, and a spiky little animal known as the spiny waterflea was added to half of the bags. This invader from Eurasia is now in 180 Ontario lakes. It’sa voracious predator of native zooplankton, which reduces the food supply for juvenile fish and other animals. In this experiment, the negative effect of the spiny waterflea overshadowed a minor impact of low calcium, though further experiments demonstrated how low calcium levels could also impact zooplankton in some Ontario lakes.

Arnott points out that whether it is calcium levels or invasive species, our lakes are changing and we need to decide whether or not to worry. “I could put on one hat, and say of course we have to worry about everything. But practically we can’t, we have limited resources. We have to deal with what’s most serious.” Research can help us decide when and how to act.

Because of the complexity of ecological interactions, doing sound research on the impacts of multiple stressors is difficult, but the challenge excites Arnott. She feels we need to better understand how environmental changes affect the entire ecosystem – all the way from algae to humans.

Achieving this ambitious undertaking requires more than zooplankton experiments; it requires scaling up and engaging many partners. Arnott often collaborates to extend expertise and information, and to inject diverse perspectives. The ecosystem studies she has planned involve plugging information gleaned from numerous scientists’ experiments with algae, zooplankton, and fish into a computational model, along with long-term data from the Ontario Ministry of the Environment and Climate Change. Eventually, the resulting model will represent how environmental changes over time affect a range of organisms in a lake. Her studies will make it possible to predict the future impact of combinations of stressors on algae, zooplankton, and fish.

Arnott’s ultimate purpose is to provide information to help society make important decisions. Indeed, the connection between ecology, society, and legislation is a source of hope for this scientist, whose research in Killarney Provincial Park has convinced her that legislation really can work. The Killarney region and its lakes, just south of Sudbury, were hit hard by acid rain. But when Canada introduced strong legislation “to turn down the acid rain tap, emissions in the Sudbury area were reduced by 90 per cent, and these lakes started to recover chemically, and the zooplankton are starting to recover.”

This bounce-back story belies a certain amount of resilience inherent in ecosystems. Arnott’s team has observed this capacity to adapt to changing conditions even in the face of the invasive spiny waterflea. Arnott relayed how some of this invader’s prey are escaping predation by going deep down into the water during the day.

Zooplankton, and the lakes they live in, have a devoted ally.

Judy Wearing
(e)AFFECT Issue 11 Spring/Summer 2017

Learn more about: Dr. Arnott's research