Marine protected areas enhance coral reef functioning by promoting fish biodiversity

Zachary M Topor,Douglas B Rasher,J Emmett Duffy,Simon J Brandl

doi:10.1111/conl.12638

Abstract

AbstractPreserving biodiversity and ecosystem function in the Anthropocene is one of humanity's greatest challenges. Ecosystem‐based management and area closures are considered an effective way to maintain ecological processes, especially in marine systems. Although there is strong evidence that such measures positively affect community structure, their impact on the rate of key ecological processes remains unclear. Here, we provide evidence that marine protected areas enhance herbivory rates on coral reefs via direct and indirect pathways. Using meta‐analysis and a path‐analytical framework, we demonstrate that, on average, protected areas increase the species richness of herbivorous fishes, which, in turn, enhances browsing rates on macroalgae. However, in all three regions studied (the Atlantic, Indian, and Pacific Ocean), a small subset of the herbivore assemblage accounted for the majority of browsing. Our results therefore indicate that ecosystem functioning on coral reefs may respond positively to both area closures and the protection of key species.

Highlights

Fluxes of energy and nutrients, quantified as rates of consumption, production, and decomposition of biomass, are integral to all ecosystems
By decomposing drivers of herbivore browsing on coral reefs, we demonstrate that Marine Protected Areas (MPAs) both directly and indirectly enhance an important ecosystem function on coral reefs via increases in species richness of browsing herbivores
A similar positive relationship between protection status and herbivory rate has been shown for grazing (Nash, Abesamis, Graham, McClure, & Moland, 2016), browsing (Rasher et al, 2013), or both (Bonaldo et al, 2017) at local scales, our study suggests that these effects do not depend on higher fish biomass but higher diversity in protected areas, and that these biodiversity effects are generalizable across the wide range of biotic and abiotic conditions found on Indo-Pacific coral reefs

Summary

Introduction

Fluxes of energy and nutrients, quantified as rates of consumption, production, and decomposition of biomass, are integral to all ecosystems. Experimental manipulations of species richness across ecosystems have demonstrated that more diverse assemblages often produce, consume, and decompose biomass at higher rates than less diverse assemblages (O'Connor et al, 2017), which can increase the provision of ecosystem services to humanity. This has brought biodiversity conservation into focus within management and policy circles (Isbell et al, 2017).

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