Disease Prevalence and Snail Predation Associated with Swell-Generated Damage on the Threatened Coral, Acropora palmata (Lamarck)

Allan J Bright,Caroline S Rogers,Tyler B Smith,Marilyn E Brandt,Erinn Muller

doi:10.3389/fmars.2016.00077

Abstract

Disturbances such as tropical storms cause coral mortality and reduce coral cover as a direct result of physical damage. Storms can be one of the most important disturbances in coral reef ecosystems, and it is crucial to understand their long-term impacts on coral populations. The primary objective of this study was to determine trends in disease prevalence and snail predation on damaged and undamaged colonies of the threatened coral species, Acropora palmata, following an episode of heavy ocean swells in the US Virgin Islands (USVI). At three sites on St. Thomas and St. John, colonies of A. palmata were surveyed monthly over one year following a series of large swells in March 2008 that fragmented 30 to 93% of colonies on monitored reefs. Post-disturbance surveys conducted from April 2008 through March 2009 showed that swell-generated damage to A. palmata caused negative indirect effects that compounded the initial direct effects of physical disturbance. During the 12 months after the swell event, white pox disease prevalence was 41% higher for colonies that sustained damage from the swells than for undamaged colonies (df = 207, p = 0.01) with greatest differences in disease prevalence occurring during warm water months. In addition, the corallivorous snail, Coralliophila abbreviata, was 46% more abundant on damaged corals than undamaged corals during the 12 months after the swell event (df = 207, p = 0.006).

Highlights

Physical damage to coral reefs from major storms and ocean swells has both immediate and long-term consequences (Hughes and Connell, 1999)
A second interval of waves above 3 m occurred 10 days later starting on 1 April 2100 h, and lasted 38 h until 3 April 1100 h
Physical damage was sustained by 62% of A. palmata colonies at the three study sites, and included broken branches, abrasions, and/or detachment from the substrate

Summary

Introduction

Physical damage to coral reefs from major storms and ocean swells has both immediate and long-term consequences (Hughes and Connell, 1999). Little is known about the potential secondary effects of physical disturbance on coral reef ecosystems. Increases in coral disease or “disease–like” mortality (Knowlton et al, 1990; Williams et al, 2008; Brandt et al, 2013) and predation (Knowlton et al, 1990) following damaging storms has been documented, suggesting that corals may become susceptible to secondary stressors following a physical disturbance. The energetic costs of repair may increase susceptibility to disease by lowering immune responses of the coral (reviewed in Mullen et al, 2004). Lesions caused by fragmentation could be sites for the introduction of pathogens, increasing susceptibility to disease. Lesions may attract corallivores (Brawley and Adey, 1982; Morton et al, 2002; Chong-Seng et al, 2011), which may be vectors of disease (Sussman et al, 2003; Williams and Miller, 2005; Gignoux-Wolfsohn et al, 2012)

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