Influence of lake volume on food web metrics in a freshwater fish assemblage across a small range of ecosystem sizes

Abstract

Lake size effects on food webs have been most clearly demonstrated for predator fish across large gradients in ecosystem size and species richness. We isolated the influence of lake size to assess food web metrics in six fish species with diverse ecologies across five lakes with similar lake characteristics in Algonquin Provincial Park (Ontario, Canada) using d13C, d15N, and d34S. Lake volume was a significant factor influencing food web metrics across most fish species. However, relationships between lake volume and food web metrics (trophic position, littoral carbon use, d34S, and niche area) were weak. For most species, trophic position decreased with lake volume, opposite from previous studies that included a wider range of lake sizes and biodiversity. Littoral carbon use and d34S showed negative and positive relationships with lake volume, respectively, suggesting a shift to pelagic offshore energy in larger lakes. Albeit weak, our results highlight that multiple co-occurring fish species within a community can have similar responses in littoral carbon use, trophic position, d34S, and niche area across a small range of lake sizes.