Herbivory facilitates growth of a key reef-building Caribbean coral.

Adam Suchley,Lorenzo Alvarez‐Filip

doi:10.1002/ece3.3620

Abstract

The decline of reef‐building corals in conjunction with shifts to short‐lived opportunistic species has prompted concerns that Caribbean reef framework‐building capacity has substantially diminished. Restoring herbivore populations may be a potential driver of coral recovery; however, the impact of herbivores on coral calcification has been little studied. We performed an exclusion experiment to evaluate the impact of herbivory on Orbicella faveolata coral growth over 14 months. The experiment consisted of three treatments: full exclusion cages; half cage procedural controls; and uncaged control plates, each with small O. faveolata colonies. We found that herbivorous fish exclusion had a substantial impact on both macroalgal cover and coral growth. Fleshy macroalgae reached 50% cover within some exclusion cages, but were almost absent from uncaged control plates. Critically, O. faveolata calcification rates were suppressed by almost half within exclusion cages, with monthly coral growth negatively related to overgrowth by fleshy macroalgae. These findings highlight the importance of herbivorous fishes for coral growth and the detrimental impact of macroalgal proliferation in the Caribbean. Policy makers and local managers should consider measures to protect herbivorous fishes and reduce macroalgal proliferation to enable coral communities to continue to grow and function.

Highlights

On coral reefs, scleractinian corals perform an extensive ecosystem engineering role through the calcification of structurally complex physical structures (Graham & Nash, 2013; Jones, Lawton, & Shachak, 1994)
O. faveolata calcification rates were suppressed by almost half within exclusion cages, with monthly coral growth negatively related to overgrowth by fleshy macroalgae
Our hypothesis is that herbivorous fishes restrict algal growth and that algal interaction has a negative impact on coral growth and calcification

Summary

| INTRODUCTION

Scleractinian corals perform an extensive ecosystem engineering role through the calcification of structurally complex physical structures (Graham & Nash, 2013; Jones, Lawton, & Shachak, 1994). Coral declines are often accompanied by rapid increases in macroalgae that impair the capacity of coral communities to recover (Birrell, Mccook, Willis, & Diaz-Pulido, 2008; Done, 1992; Hughes, Reed, & Boyle, 1987). Such phase shifts have been evident in the Caribbean where herbivory has been substantially reduced from historical baselines (Jackson et al, 2001; Paddack et al, 2009). Our hypothesis is that herbivorous fishes restrict algal growth and that algal interaction has a negative impact on coral growth and calcification

| MATERIALS AND METHODS

Findings

| DISCUSSION