Abstract

Anthropogenic stressors are causing widespread coral mortality in the Caribbean, leading to negative carbonate budgets and decreased structural complexity, which ultimately threatens reef functioning and ecosystem services. Trait-based analysis can build generic frameworks of how species respond to environmental change, and we use this approach to better understand implications of reef flattening on fishes. Using surveys from 3,999 Florida reef and hardbottom sites, we used boosted regression trees to model biophysical and anthropogenic factors correlated with the abundance of 109 fish species. We isolated the relative importance of structural complexity and coral cover for each species, categorizing species with positive associations as likely future “losers” (more abundant on complex reefs) or negative associations as “winners” (more abundant on flat reefs). Using Blomberg’s K, we determined phylogeny did not explain relationships with complexity or coral cover. Instead, we tested if morphological, behavioral, and functional traits mediate species’ responses to reef degradation. Eight traits explained 65% of variation of species’association with complexity, and seven traits explained 38% of association with coral cover. These findings indicate that smaller, streamlined generalists are more likely to be ecological winners on flattened reefs. Additionally, degraded reefs will likely have decreased predation, thus hindering resilience and recovery. Identifying these important traits provides a better understanding of how fishes interact with complexity and allows us to predict general assemblage-wide responses to flattening. Finally, these results suggest that specific ecological functions will be lost or severely diminished as reefs continue to degrade.

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