COS 185-2 - A comparison of the taxonomic and functional diversity of reef fish assemblages on artificial and natural reefs in the eastern Gulf of Mexico.

Abstract: Identifying species assemblage patterns is a critical first step for understanding the processes and mechanisms that drive community structure and helps to inform restoration, conservation, and management efforts. Such efforts increasingly rely on human-made structures to achieve their respective goals. However, whether human-made structures support assemblages similar to those of natural habitat is equivocal in marine systems, and prior studies have often been based on short-term datasets (i.e., 2‑3 years). We used a ten-year dataset of fish surveys performed seasonally (i.e., quarterly) on paired artificial-natural reefs in conjunction with species’ trait data to address two questions: (1) Do eastern Gulf of Mexico artificial and natural reefs support compositionally similar reef fish assemblages? (2) Do these assemblages exhibit similar functional diversity?

The study sites were arranged in pairs of artificial and natural reefs, located near each other to control for the effects of abiotic (e.g., depth, temperature), biotic (e.g., larval supply, basal resources), and socio factors (e.g., access by fishers). We used species composition and abundance data to calculate community-weighted means for eight different functional traits that broadly describe the behavior and diet of the observed reef fishes. We then used multifactor mixed-effects permutational multivariate analysis of variance (PERMANOVA) coupled with canonical analysis of principal coordinates (CAP) to evaluate differences in taxonomic- and functional-diversity by reef type. CAP ordinations suggested that artificial reefs were characterized by greater abundances of midwater or transient predators whereas benthic or demersal mesopredators were more abundant on natural reefs. This pattern was consistent across depth strata, although the explicit taxa contributing to differences varied with depth. These findings provide valuable insight regarding fish assemblage patterns across different forms of reef habitat in the eastern Gulf of Mexico. Further, the inclusion of functional diversity means that our results are more generalizable to other subtropical reef systems, whereas strictly taxonomic-based results are often regionally distinct due to the geographic distributions of explicit species.