Size Structuring and Distinct Energy Channels in a Minimally Disturbed Coral Reef Food Web

Patterns in food web structure are central to studies of species interactions, community dynamics, and ecosystem stability. Aquatic systems are typically size structured, and recent theory suggests that these food webs may also be structured as coupled energy channels. However, our understanding of food web structure in coral reef systems is largely limited to analyses of already degraded systems. Here, we use stable isotope analysis and visual census data from a minimally impacted coral reef at Kiritimati atoll to examine evidence of size structuring and coupled energy channels in a coral reef fish community. Trophic position scaled positively with body size across species and individuals, such that larger fish occupied higher trophic positions. Abundance scaled negatively with body size and, specifically, individuals sharing energy through predation (carnivorous fishes) scaled more steeply than individuals sharing a common energy source (herbivorous fishes). Our results provide novel evidence of size structuring in a diverse tropical food web that also reflect properties of coupled food webs, and indicate directions for further empirical analysis of the structure and stability of coral reef ecosystems.