Effects of Multi-chain Omnivory on the Strength of Trophic Control in Lakes |
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Authors: | Yvonne Vadeboncoeur Kevin S McCann M Jake Vander Zanden Joseph B Rasmussen |
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Institution: | (1) Biology Department, McGill University, 1205 Dr. Penfield Ave, Montreal, Quebec, H3A 1B1, Canada;(2) Center for Limnology, University of Wisconsin, 680 N. Park St, Madison, Wisconsin 53076, USA;(3) Department of Biological Sciences, Wright State University, 3640 Colonel Glenn Hwy., Dayton, Ohio 45435, USA;(4) Zoology Department, University of Guelph, Guelph, Ontario, N1G 2W1, Canada;(5) Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada |
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Abstract: | Omnivory has been implicated in both diffusing and intensifying the effects of consumer control in food chains. Some have
postulated that the strong, community level, top-down control apparent in lakes is not expressed in terrestrial systems because
terrestrial food webs are reticulate, with high degrees of omnivory and diverse plant communities. In contrast, lake food
webs are depicted as simple linear chains based on phytoplankton-derived energy. Here, we explore the dynamic implications
of recent evidence showing that attached algal (periphyton) carbon contributes substantially to lake primary and secondary
productivity, including fish production. Periphyton production represents a cryptic energy source in oligotrophic and mesotrophic
lakes that is overlooked by previous theoretical treatment of trophic control in lakes. Literature data demonstrate that many
fish are multi-chain omnivores, exploiting food chains based on both littoral and pelagic primary producers. Using consumer-resource
models, we examine how multiple food chains affect fourth-level trophic control across nutrient gradients in lakes. The models
predict that the stabilizing effects of linked food chains are strongest in lakes where both phytoplankton and periphyton
contribute substantially to production of higher trophic levels. This stabilization enables a strong and persistent top down
control on the pelagic food chain in mesotrophic lakes. The extension of classical trophic cascade theory to incorporate more
complex food web structures driven by multi-chain predators provides a conceptual framework for analysis of reticulate food
webs in ecosystems. |
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Keywords: | top down control omnivory littoral-pelagic coupling consumer-resource models trophic cascades food webs |
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