The Effect of Algal-Gardening Damselfish on the Resilience of the Mesoamerican Reef

Ángela Randazzo Eisemann,Jorge Luis Montero Muñoz,Melanie Mcfield,Jesús Ernesto Arias-González,Jenny Myton

doi:10.3389/fmars.2019.00414

Abstract

The structures, functions, and services provided by coral reef ecosystems are deteriorating worldwide. However, not all coral reefs are affected the same way, with some showing signs of resistance and/or recovery from disturbances. Understanding the drivers and feedbacks that contribute to shifts in community structure is valuable to support resilience-based management. In this study, key community variables that influence the resilience of coral reef ecosystems were examined in 64 sites of the Mesoamerican Reef (MAR) monitored in both 2006 and 2016, as part of the Healthy Reef Initiative (HRI), using the Atlantic and Gulf Rapid Reef Assessment (AGRRA) monitoring protocol. Based on benthic cover thresholds, sites were classified into three different states: coral state (CS) with >10% live coral and 10% live coral and >5% fleshy macroalgae and; depauperate coral state (DCS) <10% live coral. The associations between site states and the density of different fish functional groups were analyzed to determine their effects on coral reef resilience. The results highlight that territorial herbivores (algal-gardening damselfish) may play a key role in maintaining positive feedbacks towards macroalgae-stressed states. This supports the recommendation of reinforcing Marine Replenishment Zones (MRZ) in order to promote healthy populations of resident predator fish (like groupers and snappers), which could potentially regulate algal-gardening damselfish populations and diminish negative cascade effects on coral reefs. Collaborative and resilience-based management will continue to be promoted by the HRI partners, supporting the establishment of additional MRZs along with ongoing efforts to directly protect herbivorous fish (surgeonfish and parrotfish) and to improve water quality, through better wastewater treatment, watershed management and coastal development plans, with the purpose of continuing to build coral reef resilience in the MAR.

Highlights

Over the last four decades, degradation of coral reef ecosystem structures and functions have been reported worldwide (Gardner et al, 2003; De’ath et al, 2012; Birkeland, 2015; Bruno and Valdivia, 2016; Hughes et al, 2017) impacting human wellbeing through the erosion of ecosystems services (Moberg and Folke, 1999; Birkeland, 2015; Norström et al, 2016)
Only 23% of the sites were in a coral state (CS), and 77% were in a stressed coral state (SCS), considering the
In contrast to the global context of coral reef ecosystem degradation, slight improvements in reef health have been reported in the Mesoamerican Reef (MAR) over the last decade when the full set of over 300 monitoring sites are included (2006–2016), linked with coral cover and herbivorous fish increases (Mcfield et al, 2018)

Summary

Introduction

Over the last four decades, degradation of coral reef ecosystem structures and functions have been reported worldwide (Gardner et al, 2003; De’ath et al, 2012; Birkeland, 2015; Bruno and Valdivia, 2016; Hughes et al, 2017) impacting human wellbeing through the erosion of ecosystems services (Moberg and Folke, 1999; Birkeland, 2015; Norström et al, 2016) This global trend is due to a combination of anthropogenic stressors acting both on large scales (e.g., ocean acidification, sea level rise, and increases in seawater temperature) as well as locally (e.g., dredging, pollution, and overfishing). From a resilience-based management perspective and in order to overcome “wicked” resilience dynamics (sensu Glaser et al, 2018), it is key to understand changes in critical feedbacks of the system, which diminish coral reef resilience and drive the reorganization to undesirable and strongly resilient states (Walker et al, 2004; Graham et al, 2013; Glaser et al, 2018)

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Conclusion