Predators and Habitat Shape Reef Fish Communities in Surprising Ways, Study Finds

We wanted to understand how predators and habitat characteristics interact to shape fish populations on coral reefs.

We conducted field surveys and controlled experiments in Moorea's lagoon, manipulating both grouper presence and habitat characteristics on coral patch reefs. What they found surprised them: groupers reduced prey abundance by 50% and gamma diversity by 45%, with a disproportionate removal of rare species relative to common species - 64% and 36% reduction, respectively. There was also a 77% reduction in beta diversity.

But here's what caught them off guard: predators and patch characteristics had completely independent effects. Larger patches contained more fish, with a doubling of patch size leading to a 36% increase in prey abundance, but this effect didn't change whether groupers were present or absent. Even more unexpectedly, fragmented patches had 50% higher species richness than unfragmented patches of the same total area.

The independence of these effects wasn't what We expected. Theory predicted that predators would modify the species-area relationship, but they didn't. We showed that groupers increased the importance of stochastic community assembly relative to patches without groupers through null model analysis.

These findings matter because they suggest that natural and anthropogenic processes affect reef fish biodiversity through two separate pathways rather than one integrated system. As coral reefs face increasing pressure from development, fishing, and climate change, Our results indicate that managing predator populations and habitat structure require independent strategies. You can't assume that protecting large, continuous habitats will automatically account for predation effects, or vice versa.

The study reveals the complexity of reef ecosystem dynamics and challenges existing theoretical predictions about how predators and habitat characteristics interact to shape marine communities.

Citation

Stier, Adrian C.; Hanson, Katharine M.; Holbrook, Sally J.; Schmitt, Russell J.; Brooks, Andrew J. (2014). Predation and landscape characteristics independently affect reef fish community organization. Ecology.

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