Multi-Scale Relationships Among Physical Habitat Characteristics and Habitat Coupling By Largemouth Bass in Reservoirs

Variation in food web structure among ecosystems can have consequences for interactions such as competition, resource dynamics, and the accumulation of contaminants by higher trophic levels. Therefore, the understanding of mechanisms that affect the patterns of energy flow and habitat coupling by higher trophic levels among ecosystems is important. Reservoir ecosystems are dynamic environments that are often influenced by a range of both natural and anthropogenic factors, however, there has been little prior work investigating the factors that drive variation in food web structure in these systems. We examined the influence of a range of physical and chemical features measured at several spatial scales on the proportional reliance of largemouth bass on benthic versus pelagic resources across 14 Illinois reservoirs. Using stable isotopes signatures of benthic and pelagic invertebrates as baselines we found that largemouth bass reliance on benthic resources and mean trophic position decreased sharply with factors related to nutrient enrichment and the loss of submerged aquatic vegetation. Percent benthic reliance, trophic position, and submerged aquatic vegetation coverage decreased with increasing lake order, agricultural watershed land use and common carp relative abundance. Our results highlight the effects of eutrophication and invasive species on food web structure of reservoir ecosystems.