Functional change in coral reef communities across an inshore to offshore environmental gradient

Background/Question/Methods

Background environmental gradients naturally shape ecosystem processes and functions. In recent centuries, anthropogenic disturbances at local and global scales have altered environmental conditions, reshaping ecosystem function across space and time. As global disturbances increase under climate change, it remains imperative that we are better able to track and predict resulting changes in ecosystem function across variable background environmental conditions. Functional trait data can offer insight into the mechanisms underlying higher level changes in community composition and ecosystem structure. In coral reef ecosystems, diversity of coral traits and life histories has been shown to affect habitat complexity and predict the structure of fish assemblages, upon which subsistence fisheries rely. However, few studies have used trait-based methods to assess variation in coral reef community composition and function across environmental gradients altered by anthropogenic disturbance. Here, we use functional trait and species abundance data to quantify spatial and temporal variation in the composition and function of 11 coral reefs across an inshore to offshore environmental gradient in Bocas del Toro, Panama. Specifically, we assess changes in benthic cover, coral species, and coral functional traits over a period of 15 years and 3 bleaching events.

Results/Conclusions

Our results reveal that the composition and function of inshore and offshore reefs in Bocas del Toro were distinct and shaped by an environmental gradient likely altered by local anthropogenic disturbances. Inshore reefs experienced greater losses in reef-building coral species and diversity, but both inshore and offshore reefs became functionally similar over time. These findings indicate that inshore reefs are less resilient to global disturbances than offshore reefs due to long-term exposure to local disturbances. Additionally, reef function may homogenize across background environmental conditions under climate change. This work expands on our existing knowledge of changing ecosystem function over the past few centuries and addresses the effects of prior environmental conditions on community resilience to increasing global disturbances.