Subsidy sources in small lakes: Not soup but specks and sinkers.
Pace, Michael *,1, Carpenter, Steve2, Cole, Jonathan1, Kitchell, James 2, Hodgson, James 3, Van De Bogert, Mathew2, 1 Institute of Ecosystem Studies, Millbrook, NY, USA2 Center for Limnology, Madison, WI, USA3 Dept. of Biology, De Pere, WI, USA
ABSTRACT- Half or more of the secondary production in several small lakes was supported by terrestrial subsidies based on a series of whole lake carbon-13 additions. We evaluated the importance of terrestrial sources using a carbon flow model that traces the movement of C-12 and C-13. The largest source of terrestrial carbon to the experimental lakes is dissolved organic matter (soup). This material supports considerable bacterial respiration. However, bacterial biomass and production are not sufficient to provide much terrestrial carbon to consumers. Hence, relatively little of the soup moves up the food web to consumers. Model analysis indicates direct utilization of particulate organic matter (specks) of terrestrial origin is important to many invertebrates. Predatory fish also consume terrestrial organisms (sinkers) including insects, snakes, birds, voles, shrews, and mice. Fish carbon is partially derived from the episodic utilization of sinkers plus flows of terrestrial particulates to aquatic invertebrates and subsequent consumption of these invertebrates. Overall, the labeling patterns of C-13 observed in invertebrates and fishes during the whole lake additions can only be fit when substantial fluxes of terrestrial particulates and organisms are included in the model.
Key words: Subsidies, Food Webs, Lakes, Carbon Isotopes
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