How much do we really know about the responses of lakes to climate change?
Ann Arbor, MI — How strong is the signature of local weather conditions and large-scale climatic variability on the physical (e.g., temperature, timing of stratification, duration of ice cover), chemical (e.g., nutrient concentrations), and biological (e.g., timing of the spring bloom, phytoplankton composition, zooplankton abundance) characteristics of the lakes? Which direct and indirect mechanisms drive these ecological patterns?
A new study addresses these questions by reviewing what we have learned from several relatively well-studied north-temperate deep lakes (e.g., Lake Washington, Lake Tahoe, Lake Constance, Lake Geneva, Lake Baikal, Lake Zurich) with respect to the ability of climate in modulating the interplay among lake hydrodynamics, chemical factors, and food web interactions.
"We intentionally selected deep systems because they offer the opportunity to study the impact of climate change on a range of mixing regimes of the physical lake typology", says George Arhonditsis, a Professor at the University of Toronto.
"Indeed, more than anything else, our study shows that the primary response to external meteorological forcing has been the increase in overall lake and (especially) epilimnetic temperatures, the increase in thermal stability, the lengthening of stratification period and/or shortening of the ice cover period of several well-studied north temperate deep lakes," says Arhonditsis.
"Interestingly, the response of the biotic communities to the changing weather conditions has been less clear and sometimes the findings from different lakes are contradicting," says Yuko Shimoda, a graduate student at the University of Toronto, who completed her M.Sc. research paper working on this topic.
The same study emphasizes the importance of two complementary directions of future research: first, the need to elucidate the wide array of in-lake processes that are likely to be affected by climate change; and, second, the need to examine the heterogeneity in responses among different water bodies. The rationale of this approach and its significance for dealing with the uncertainty that the climate signals cascade through lake ecosystems and shape abiotic variability and/or biotic responses has been recently advocated by several other review papers.
Regarding the former direction of research, Arhonditsis cautions that "much of our contemporary understanding has been based on empirical evidence from offshore areas, while the interactions with the nearshore zones have largely been neglected. Ironically, in many large lakes, the most degraded areas are nearshore zones. We believe that the classical two dimensional conceptualization (time and depth in an offshore site) has been sufficient to bring us here, but any further advancements of our understanding of the climate-induced changes on lake phenology should be based on more integrative frameworks that consider as one of the focal points the interplay among watershed, nearshore and offshore lake areas."
Original Publication Information
Results of this study, "Our current understanding of lake ecosystem response to climate change: What have we really learned from the north temperate deep lakes? ," are reported by Yuko Shimoda, M. Ekram Azim, Gurbir Perhar, Maryam Ramin, Melissa A. Kenney, Somayeh Sadraddini, Alex Gudimov and George B. Arhonditsis in the latest issue (Volume 37, No. 1, pp. 173-193) of the Journal of Great Lakes Research, published by Elsevier, 2011.
Contacts
For more information about the study, contact George Arhonditsis, Department of Physical & Environmental Sciences, University of Toronto, Toronto, Ontario, Canada, M1C 1A4, georgea@utsc.utoronto.ca, 1 416 208 4858.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, Environment Canada, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; jglr@ec.gc.ca; (306) 975-5310.
Since 1967, IAGLR has served as the focal point for compiling and disseminating multidisciplinary knowledge on North America's Laurentian Great Lakes and other large lakes of the world and their watersheds. In part, IAGLR communicates this knowledge through publication of the Journal of Great Lakes Research, available to members in print and electronic form. A searchable archive of the journal is available online and includes the abstracts of articles from the journal's inception in 1975 through the most recent issue. In addition, complete articles are available to members who have signed up for an electronic subscription.