Trophic niche overlap in coralline algae- and coral-dominated rocky-bottom subtidal communities

Abstract

We investigated trophic structures in rocky subtidal ecosystems transitioning from canopy-forming to barren states across coastlines with varying oceanographic conditions. We examined stable isotopes and functional traits of common invertebrate and fish taxa to understand the food-web consequences. We hypothesized that resource exploitation patterns of functional guilds would result in distinct isotopic niches, defining trophic diversity and niche. δ13C and δ15N ranges of invertebrate functional groups differentiated pelagic from benthic trophic pathways, reflecting flexible dietary use in the absence of macroalgae. Fish production relied on prey using pelagic and benthic basal resources. Trophic redundancy among consumers within functional guilds contributed to intrinsic trophic structure in barren ecosystems. The resulting community-wide trophic diversity has led to consistent niche widths and overlapping niche space. Overall, our findings highlight the crucial roles of consumers that persist with diverse functional guilds in conferring the adaptability of barren rocky ecosystems following habitat disturbance. © 2024