Evaluating Spatial Variation in Lake Superior Food Web Connectivity

Session: 34. - Aquatic Habitat Evaluation and Assessment

Marissa Wegher, Lakehead University, [email protected]
Aaron Fisk, University of Windsor, [email protected]
Timothy Johnson, Ontario MNRF, Glenora Fisheries Station, [email protected]
Michael Rennie, Lakehead University, [email protected]

Abstract

Nearshore-offshore coupling (NOC) integrates energy between habitats, a process known to contribute to food web stability and resiliency, and has been observed in Lake Superior. The degree of NOC differs among species, but the extent to which NOC varies across Lake Superior is unknown. A change in the degree of NOC may also alter regional trophic transfer efficiency (TTE). To evaluate spatial differences in NOC and TTE among fishes in Lake Superior, common species and their prey were collected from four regions. For each species habitat coupling was assessed using stable isotope analysis, and TTE (conversion efficiency) was assessed using bioenergetic models. NOC was expected to be highest in Keweenaw and lowest in Nipigon Bay due to the lake morphometry. Raw stable isotope analysis supported these results using the offshore specialist smelt. Nipigon Bay had significantly higher ?C¹³ than those of the other three regions, suggesting less or no NOC. Incorporating baseline variation will clarify these comparisons. Differences in TTE among the four regions were also found for smelt; the highest in Whitefish Bay and lowest in the Western Arm. This work will contribute to a better understanding of the inherent variation in ecosystem function across large lake ecosystems.

1. Keyword
Lake Superior

2. Keyword
Spatial analysis

3. Keyword
stable isotopes