Research in the lab



My group’s long-term research goal is to understand the impacts of multiple environmental stressors on the million lakes of the Canadian Shield, one of the world’s foremost freshwater resources. Our focus is on the key pelagic herbivores of these lakes - the animal plankton.

My interest in multiple stressors began in graduate school, with my MSc research on the effects of acid rain on phytoplankton, and my doctoral program on the regulation of metal bioaccumulation by animal plankton. With this applied science background, I joined the Ontario Ministry of the Environment (MOE) for 25 years of work on what can go wrong with our lakes, and how the damage can be fixed. In 2000 I joined the Biology Department at York, and I split my time between York University, and the MOE’s Dorset Environmental Research Centre (DESC), 2.5 hours north of Toronto near Algonquin Park. The DESC lies in beautiful forested landscape dotted with 1000’s of lakes - our study sites. In partnership with the government, I have built the FLAMES lab, the Field Laboratory for the Assessment of Multiple Ecological Stressors, at the DESC, and it is the research home for most of my graduate students. My current main areas of research are: (1) determining the individual and joint impacts on aquatic food webs of non-indigenous species and (2) changes in climate, acidity, calcium, and nutrients, and (3) quantifying the regulators of recovery of lakes from past environmental damage. Our lab has been quite productive, authoring over 100 publications. and receiving several awards of excellence for our work, but I gain most satisfaction from the knowledge that our research has both contributed to improved management of Ontario’s lakes, and led, on occasion to substantial and sustained recovery of lakes and their biota from historical damage (paper1, paper2). The current most active areas of research in the lab are:

The spread and impacts of Aquatic Invading Species, eg. the spiny water flea

Next to habitat loss, the introduction of non-indigenous species is the most important cause of global biodiversity loss. We are seeking to understand the current and future threat of non-indigenous species to the lakes of the Canadian Shield. Our model species is the spiny water flea, Bythotrephes (right).

 It was brought to North America in ship ballast water, and introduced into the Great Lakes. We first found it in the lakes of Muskoka in 1989, and it has since spread to almost 50 lakes in the region. Bythotrephes is a very damaging invader leading to 30-40% reduction in native biodiversity of animal plankton. We were the first in North America to document the spread of Bythotrephes into inland lakes, and to document its damaging affects on native biota (Yan et al. 2002, Yan and Pawson 1997, Boudreau and Yan 2003). There are currently 5 Bythotrephes graduate projects in the lab. With a large crew of helpers, we sampled 300 lakes in Muskoka to document the current invasion situation. For her PhD, Joelle Young is developing a deep understanding of the ecology and life history of the invader in lakes with different fish assemblages. Erika Weisz’ MSc is focused on habitat invasibility by Bythotrephes, and its interaction with competing macroinvertebrate predators. In her MSc, Jen Petruniak is identifying weather conditions that favour mass Bythotrephes dispersal down lake outflows. Finally, Natalie Kim’s MSc research is designed to identify the physical and chemical factors in receiving waters that affect the probability of establishment of Bythotrephes colonists.

Ca decline

Canadian Shield lakes normally have soft waters, i.e. waters with low concentrations of calcium (Ca), but Ca levels are currently in decline, and no one knows what the effects of this decline might be. Ca in Shield lakes are controlled by free Ca levels in forest soils, and the levels in forest soils are falling because input rates from mineral weathering and atmospheric deposition are lower than loss rates attributable to logging and acid deposition. All living creatures require Ca, but we do not know what Ca concentrations are limiting for biota on the Shield, nor how the Ca thresholds might interact with ongoing nutrient decline and climate warming. As Ca levels are declining across the Shield, as requirements for Ca differ greatly among species, and as the effects of low Ca are exacerbated at high temperatures, we see research on effects of Ca decline as an urgently need. What we currently know about the impacts of Ca decline on zooplankton comes mainly from the research of two recent students in our lab – Dawn Ashforth and Adam Jeziorski. Dawn alerted us to the potential for interactions of Ca decline with global warming. Adam identified the remarkable inter-species differences in Ca requirements. Two new MSc students will build on this pioneering work. Christine Gibson will determine the temperature and pH-dependency of Ca thresholds of several Ca-rich zooplankton species. Allegra Cairns will test these Ca thresholds in the field, determining if there is predictable damage once the thresholds are passed. I believe that the interaction of Ca decline with global warming is a critical emerging environmental issue for large regions of the world’s soft-water lakes.

                                                           Daphnia –a Ca-rich species

Impacts of multiple stressors, including climate change

There is a growing realization among applied ecologists that it no longer makes sense to study the impacts of environmental stressors in isolation, given the reality of multiple stressors in nature. Lakes on the Canadian Shield are now facing both good changes, eg. recovery from acidification and oligotrophication, and many potential damaging stressors, including road salt additions, base cation decline, climate change and the spread of invading species. Research on the joint effects of these multiple stressors is in its infancy. Much of my own specific work is in this field, for example (Yan et al., in press). Michelle Palmer’s PhD will build on this field of work in our lab. Michelle is quantifying changes that are occurring in response to multiple stressors in three regions with long-term and large scale data set, i.e. Dorset, Sudbury and Wisconsin.

Recovery from historical damage

One real test of ecological knowledge is if we can understand inter-species and species-habitat relationships well enough to restore ecosystems from historical damage. As I have been working on recovery of lakes from acidification and metal contamination for more than two decades, I am convinced that there is no more satisfying field of work for an applied ecologist than restoration ecology. Given its importance I am joined in this work by colleagues from several Ontario and Canadian environmental agencies, and colleagues from other countries, especially Norway, in a wide-ranging research program. For example, we have been able to demonstrate complete recovery of entire species assemblages from chronic and severe damage. Carrie Holt’s MSc research documented regional scale recovery of zooplankton near Sudbury, the first time this has been demonstrated. With collaboratoring physicists we are exploring if tree planting and recovery from acidification are responsible for the profound cooling of Sudbury lakes, a cooling that is occurring despite global warming. Martha Celis-Salgado’s PhD research will determine if current, residual metal contamination is regulating the recovery of zooplankton in Sudbury. Much of this work is performed on Sudbury lakes, and here we work in close collaboration with scientists from Laurentian University’s Co-operative Freshwater Ecology Unit.







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