TESTING THE ECOSYSTEM SIZE AND PRODUCTIVE SPACE HYPOTHESES IN ALPINE LAKES

This study evaluates two competing hypotheses for what regulates the architecture of food webs in California mountain lakes: ecosystem size or productivity. We measured food chain length and six multidimensional isotopic niche space measures in 36 mountain lakes representing varying lake volume and productivity dynamics. We demonstrate a modicum of support for the ecosystem size hypothesis, but no support for the productive space hypothesis. Across lakes ranging vastly in volume (8,773 – 3,999,753 m³), food chain length, and all multidimensional isotopic space niche measures showed positive trends with ecosystem size. However, only three measures (trophic area, niche centroid distance, and δ¹³C range) scaled significantly. There were no significant relationships between lake productivity and any of the six community niche metrics. Aquatic insects supported fish consumers in all lakes. However, reliance of consumer fishes on terrestrial insects and periphyton increased significantly and non-linearly with lake size, while reliance on aquatic plants showed opposite trends.  These results expand understanding of the biogeography of aquatic food webs, and contextualize how ecosystem size and productivity drive trophic links in mountain lakes specifically.  

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Christine Parisek, University of California - Davis (caparisek@ucdavis.edu)

Authors:

Sophie Sanchez, University of California Davis | Wildlife, Fish, & Conservation Biology  (sosanc@ucdavis.edu)

Steve Sadro, University of California Davis | Environmental Science & Policy  (ssadro@ucdavis.edu)

Robert Lusardi, University of California Davis | Wildlife, Fish, & Conservation Biology  (ralusardi@ucdavis.edu)

Andrew Rypel, Auburn University | School of Fisheries, Aquaculture and Aquatic Sciences  (rypel@auburn.edu)