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Graduate Program in Biology

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Norman D. Yan

Norman D. Yan

PhD (Guelph)
Professor of Biology

E-mail: nyan@yorku.ca

Research Areas: Ecology and Plankton Population Biology, Limnology, Biological Invasions, Restoration Ecology

Norman D. Yan

Canadian ecosystems are currently challenged by many local, regional and global environmental stressors including the introduction of exotic species, climatic change and stratospheric ozone depletion. My long-term interest is quantifying the effects of these and other man-made stressors on the life in Canadian Shield lakes, particularly on their animal plankton, or zooplankton. Zooplankton are good target organisms for such work because of their diverse life styles, ecological responsiveness, and ease of sampling. Over the years I have quantified the impacts of many different stressors, including acid rain, trace metals, nutrients, protozoan parasites, exotic invaders, and vertebrate and invertebrate predators. I have also provided the technical justification to foster recovery of lakes from such damage. To do this I have used and continue to use a variety of research approaches, including whole-lake manipulation experiments, laboratory bioassays, bioenergetic modelling, and large-scale and long-term surveys. This methodological mix reflects my enjoyment of collaborative research, and my emphasis on sound field work. My broad research focus also reflects my desire to provide information of significance to both ecologists and to lake managers.

Currently, I have five principal research interests. First, because so many of our ecosystems have been historically damaged, I am attempting to identify the key factors that regulate the recovery of lakes from historical damage. I am using acid and metal damage as my model stressors, with work on severe historical damage conducted in and around Sudbury, Ontario. Given their similar acid rain history, several Scandinavian colleagues are collaborating with me in this research. There are many challenging and interesting complexities in the ecological recovery process and a simple return to the pre-damaged state should not be anticipated. Secondly, I am attempting to determine the influence of nonindigenous species – the second largest global source of biodiversity loss – on Ontario’s lakes. Several Eurasian invertebrates have recently invaded the Great Lakes and are now spreading inland. I am quantifying the effects of one key invader - the Eurasian spiny water flea, Bythotrephes - on aquatic ecosystem function and aquatic resource quality in Ontario's inland lakes. Thirdly, I am exploring the influence of climatic change on the zooplankton of Shield lakes, working with my provincial government colleagues who have generated some of the finest long-term zooplankton data sets in existence. Fourthly, as ambient lakewater Ca concentrations are currently falling in eastern North American softwater lakes, two of my new students are beginning a new research program, exploring the influence of falling Ca concentrations on crustacean zooplankton. Finally, I am exploring the interactive impacts of multiple environmental stresses on Ontario’s inland lakes. For example, our lab is assembling evidence that the joint effects of climate change and acidification cannot be predicted from an examination of the individual impacts of these two stressors. We are also beginning to recognise linkages between contaminant partitioning and the introduction of exotic species.
Much of my, and my students’ field work is executed in partnership with Ontario government scientists at their laboratories near Dorset and Sudbury, Ontario. These locations are ideal for limnological research because of the number and biogeochemical diversity of nearby lakes and the excellence of the available historical and recent data series. In 2002 I was awarded a CFI grant to construct a laboratory designed for research on impacts of multiple ecological stressors on zooplankton. This facility is currently under construction at the Dorset site, and will be operational in the spring of 2004. It will greatly enhance our lab’s research capabilities.

A small selection of my recent publications follow. These provide examples, respectively, of my work on the following topics: the possibilities for (1) and conceptualisation (2) of recovery of biota from historical acidification, (3) climatic influences on process of recovery from acidification, (4) the influence of introduced fish, and (5,6) introduced invertebrate predators on aquatic biota, and (7) the interactions of climate change, acid rain and stratospheric ozone depletion on lakes. This applied research is built on a strong foundation of the basic biology of zooplankton, for example, their biodiversity (8), spatial (9) and temporal (10) variability, and their demography (11).



1. Holt, C.A. and N.D. Yan 2003. Recovery of zooplankton communities from acidification in Killarney Park, Ontario, 1972-2000: pH 6 as a recovery goal. Ambio 32: 203-207.

2. Yan, N.D., B. Leung, W. Keller, S. E. Arnott, J. M. Gunn, and G.G. Raddum. 2003. Developing a conceptual framework for the recovery of aquatic biota from acidification: a zooplankton example. Ambio 32: 162-164.

3. Arnott, S.E., N.D. Yan, W. (Bill) Keller and K. Nicholls. 2001. The influence of drought-induced acidification on the recovery of plankton in Swan Lake. Ecol. Applicat. 11: 747-763.

4. Yan, N.D., A. Pérez-Fuentetaja, C.W. Ramcharan, D.J. McQueen, E. Demers and J.A. Rusak. 2001, Changes in the crustacean zooplankton communities of Mouse and Ranger Lakes – Part 6 of the Dorset food web piscivore manipulation project. Archiv Hydrobiol, Spec. Issues Advanc. Limnol. 56: 127-150.

5. Yan, N.D. and T.W. Pawson. 1997. Changes in the crustacean zooplankton community of Harp Lake, Canada, following invasion by Bythotrephes cederstroemi. Freshwater Biol. 37: 409-425.

6. Boudreau, S.A. and N.D. Yan. 2003. the differing crustacean zooplankton communities of Canadian Shield lakes with and without the nonindigenous zooplanktivore Bythotrephes longimanus. Can. J. Fish. Aquat. Sci. in press.

7. Yan, N.D., W. Keller, N.M. Scully, D.R.S. Lean and P.J. Dillon. 1996. Increased UV-B penetration in a lake owing to drought-induced acidification. Nature. 381:141-143.

8. Yan, N.D., R. Girard and S. Boudreau. 2002 An introduced predator (Bythotrephes) reduces zooplankton species richness. Ecology Letters 5: 481-485

9. Rusak, J.A., N.D.Yan, N.D., K.M. Somers, K. L. Cottingham, F. Micheli, S.R. Carpenter, T.M. Frost, M.J. Paterson, and D.J. McQueen. 2002. Temporal, spatial, and taxonomic patterns of crustacean zooplankton variability in unmanipulated north-temperate lakes. Limnol. Oceanogr. 47: 613-625

10. Rusak, J., N.D.Yan, K.M. Somers and D.J. McQueen. 1999. The temporal coherence of zooplankton population abundances in neighbouring north-temperate lakes. Am. Nat. 153: 46-58.

11. Yan, N.D. A. Blukacz, W.G. Sprules, P. K. Kindy, D. Hackett, R. Girard and B. J. Clark. 2001. Changes in the zooplankton and the phenology of the spiny water flea, Bythotrephes, following its invasion of Harp Lake, Ontario, Canada. Can. J. Fish. Aquat. Sci. 58: 2341-2350.