Seasonal rearrangements in the use of coastal habitat mosaics by tropical fishes create a cyclic functional trajectory

Abstract

Coastal habitat mosaics are among the most productive ecosystem on earth, having important functions for fish species throughout their life cycle. The complex dynamic of these areas, marked by constant changes in environmental conditions, creates spatial and temporal rearrangements of assemblages that may have significant impacts on ecosystem functioning. Thus, this study aimed to assess how seasonal variations in species composition affect the diversity of functions in these areas. We identified functional guilds of fish species found in three coastal habitat mosaics and used their functional traits as indicators of ecosystem functionality. Our results demonstrated that coastal habitat mosaics exhibit significant spatial and temporal variations in both, guilds, and functions, with remarkable differences in between-habitat responses to the onset of the tropical rainy season. More specifically, we found that mangroves exhibit a clear linear relationship between rainfall and functions, whereas in seagrass beds, functional diversity increases at low levels of rainfall and decreases at high levels. Lastly, sandy beaches have its functions increased by rainfall, but reaches an asymptote. These patterns point out to habitat-specific functional trajectories through time, which can be explained by the movements of species through the coastal mosaic in response to environmental variability, and to ontogenetic migration as species grow.