COS 22-7 - Climate change and the structure of lake food webs

Tuesday, August 9, 2011: 10:10 AM
8, Austin Convention Center
Tyler D. Tunney1, Kevin S. McCann1 and Brian J. Shuter2, (1)Integrative Biology, University of Guelph, Guelph, ON, Canada, (2)Ecology & Evolutionary Biology, University of Toronto, Toronto, ON, Canada

That climate change profoundly alters ecosystems and thus potentially threatens the way they function is widely accepted among ecologists. Despite interest in the incidence of climate driven biodiversity changes, relatively few studies examine the influence of climate on the structure and function of nature’s diverse food web interactions. Recent systems theory argues that the complex structures that comprise food webs can exhibit a capacity to respond adaptively in the face of changing conditions. Here we use ideas from this developing theory to predict how changing climate alters fundamental structure and the function of freshwater food webs containing lake trout (Salvelinus namaycush). Specifically, we argue that as surface waters warm above preferred conditions, foraging in these waters becomes metabolically costly, and thus littoral (near-shore) prey is less accessible to cold water predators like lake trout. Consequently, we predict that food chains in these warm littoral habitats become decoupled from consumers that prefer colder pelagic (off-shore) habitats. Using stable isotopes we empirically test this idea by documenting food web structure in a large number of lakes across a range in summer climate greater than 10°C.


Preliminary results show that in colder areas pelagic and littoral zones are consistently coupled by the top predator but in warmer areas the degree of coupling becomes more variable. Importantly, through a link to thermal habitat, we find that climate influences the potential for habitat coupling in lakes, and thus appears to modify the built-in responsive capacity of these ecosystems. We expect that where climate change is drastic, these modifications may reduce the natural ability of many systems to buffer against other forms of environmental variation. We end by further discussing the implications of climate warming for the persistence of systems, and our continued use of their valuable resources.

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