Small-scale spatial pattern of the trophic structure of polychaetes from coral reefs: Implications of future sea level rise

The functional ecology of macrobenthic communities, particularly their trophic structure, is crucial for understanding ecosystem response to disturbances. The present study provides the first characterization of the small-scale spatial distribution patterns of polychaete feeding guilds in the midlittoral and shallow infralittoral of a tropical coral reef. The aim of this study was to analyze the small-scale vertical distribution of polychaete feeding guilds at the interface between the midlittoral and shallow infralittoral of a reef environment, using artificial substrate units (ASUs). Our results indicated that the most dominant polychaete group was SR-He-mic (herbivore feeding on surface benthic microbiota), followed by SR-De (feeding on surface deposits). The distribution of guilds was influenced by tidal height, with trophic group richness increasing from the midlittoral to the infralittoral. However, the distribution of organisms in the trophic groups was more equitable in the midlittoral zone, without the strong dominance of a single group. In contrast, tidal heights −0.3 m and −0.4 m were dominated by SR-De (feeding on surface deposits), showing slightly lower diversities although with high variation in values. Thus, trophic structure is expected to change significantly in the event of “drowning” (total or partial) of the reef ecosystem, with rising sea levels increasing the dependence of the ecosystem on deposited organic matter. This study highlights that the vertical zonation of the trophic structure of polychaetes plays a critical role in determining the vulnerability of the coral reef ecosystem to climate change, emphasizing the necessity and importance of mitigation actions to prevent significant changes in this ecosystem.