Functional diversity metrics detect temporal changes and spatial differences in the fish communities of a Caribbean MPA

MARTHA PATRICIA RINCÓN DÍAZ; SIMON PITTMAN; IVAN ARISMENDI; SELINA HEPPELL

Ecosphere

Wiley Periodicals, Inc.

Lugar: NJ; Año: 2018

Functional diversity (FD) metrics quantify the trait diversity in biological assemblages and act as a proxy for the diverse ecological functions performed in the community. Analyses of FD offers a potentially useful tool to identify functional changes in diverse, complex, and disturbed marine ecosystems such as coral reefs, yet this metric is rarely applied to evaluate community change. Here, we document spatio-temporal variability in the trophic function of fish assemblages to identify changes in coral reef communities inside the Buck Island Reef National Monument (BIRNM) in the U.S. Virgin Islands between 2002 and 2010, which include an intense coral bleaching event in 2005. We combined six trait categories related to the trophic function of 95 fish species together with species biomass estimated from underwater surveys to calculate assemblage-level descriptors of functional richness, dispersion, and evenness. We tested the effects of habitat type, time, and their interaction on fish FD using a non­parametric permutational multivariate analysis of variance. We found statistically significant differences for functional richness and dispersion, suggesting that changes in trophic trait composition and abundance vary by habitat and time. Coral reef and other hard bottom areas supported high levels of trophic functional richness and variation among habitat types, but with low functional redundancy evidenced by the unique functional role that each fish species had within the functional trait space. These results suggest that a significant decline in fish diversity in the BIRNM would likely result in loss of trophic functions from the community. Important temporal variations in functional trait composition during the last decade in the BIRNM, including change following the strong coral bleaching event in 2005, suggest that functional diversity descriptors are sensitive enough to track shifts in the trophic organization of fish communities. In addition, we show a new way to monitor resilience by plotting the centroid of the functional trait space formed by fish communities through time. Collectively, our findings demonstrate the utility of functional diversity descriptors to evaluate changes to the functional integrity of diverse and spatially heterogeneous habitats across the seascape.