Shifts in Macrobenthic Assemblage on Red Mangrove (Rhizophora mangle L.) Prop Roots Along a Latitudinal Gradient

Mangrove prop root epifaunal communities support coastal biodiversity by providing habitat and refuge for associated sessile species and contributing to larval supply. Yet, regional surveys across latitudinal gradients in southeast Florida remain scarce. Understanding how these communities vary spatially and temporally is essential for forecasting biodiversity responses to environmental change. This study tested how macrobenthic assemblage composition and beta diversity on red mangrove prop roots vary from Key West to Melbourne, Florida. Presence-absence data from 32 sites in four zones were analyzed using beta diversity partitioning, indicator species analysis, and temporal turnover metrics. A strong biogeographic boundary near Palm Beach County delineated a species-rich southern pool, formed by the Florida Keys and Miami-Dade and characterized by tropical sponges. Of the 41 indicator species, 34 were associated with these two southern zones, while neither northern zone had exclusive indicators. Northern beta diversity was dominated by nested subsets of a larger species pool rather than species replacement. Over the three years, only Broward-Palm Beach gained species, while the other three zones lost species, though this was not statistically significant. These findings highlight the ecological significance of the potential biogeographic ecotones and provide a baseline study from which to gain insight into how climate-driven mangrove range expansion may impact coastal biodiversity and ecosystem resilience.