Disease dynamics and potential mitigation among restored and wild staghorn coral, Acropora cervicornis.

Margaret W Miller,Kathryn E Lohr,Caitlin M Cameron,Dana E Williams,Esther C Peters

doi:10.7717/peerj.541

Abstract

The threatened status (both ecologically and legally) of Caribbean staghorn coral, Acropora cervicornis, has prompted rapidly expanding efforts in culture and restocking, although tissue loss diseases continue to affect populations. In this study, disease surveillance and histopathological characterization were used to compare disease dynamics and conditions in both restored and extant wild populations. Disease had devastating effects on both wild and restored populations, but dynamics were highly variable and appeared to be site-specific with no significant differences in disease prevalence between wild versus restored sites. A subset of 20 haphazardly selected colonies at each site observed over a four-month period revealed widely varying disease incidence, although not between restored and wild sites, and a case fatality rate of 8%. A tropical storm was the only discernable environmental trigger associated with a consistent spike in incidence across all sites. Lastly, two field mitigation techniques, (1) excision of apparently healthy branch tips from a diseased colony, and (2) placement of a band of epoxy fully enclosing the diseased margin, gave equivocal results with no significant benefit detected for either treatment compared to controls. Tissue condition of associated samples was fair to very poor; unsuccessful mitigation treatment samples had severe degeneration of mesenterial filament cnidoglandular bands. Polyp mucocytes in all samples were infected with suspect rickettsia-like organisms; however, no bacterial aggregates were found. No histological differences were found between disease lesions with gross signs fitting literature descriptions of white-band disease (WBD) and rapid tissue loss (RTL). Overall, our results do not support differing disease quality, quantity, dynamics, nor health management strategies between restored and wild colonies of A. cervicornis in the Florida Keys.

Highlights

Disease, in conjunction with co-occurring and likely interacting stressors such as storms and warming temperatures, is the major driving factor placing the Caribbean staghorn coral, Acropora cervicornis, at risk of extinction
Most authors apply the historical label of white-band disease (WBD) (Aronson & Precht, 2001; Gignoux-Wolfsohn, Marks & Vollmer, 2012; Gladfelter et al, 1977; Peters, 1984; Vollmer & Kline, 2008), a condition that was first described in A. palmata from Tague Bay, St
Surveillance of multiple wild and restored populations of staghorn coral in the Florida Keys during two years emphasizes the severe, ongoing disturbance that disease invokes in this endangered species

Summary

Introduction

In conjunction with co-occurring and likely interacting stressors such as storms and warming temperatures, is the major driving factor placing the Caribbean staghorn coral, Acropora cervicornis, at risk of extinction (reviewed in Aronson & Precht, 2001; IUCN, 2012). Most authors apply the historical label of white-band disease (WBD) (Aronson & Precht, 2001; Gignoux-Wolfsohn, Marks & Vollmer, 2012; Gladfelter et al, 1977; Peters, 1984; Vollmer & Kline, 2008), a condition that was first described in A. palmata from Tague Bay, St. Croix, US Virgin Islands, as “a sharp line of advance where the distally located, brown zooxanthella-bearing coral tissue is cleanly and completely removed from the skeleton, leaving a sharp white zone about 1-cm wide that grades proximally into algal successional stages. A second type of WBD was recognized in the 1990s, WBD-II, distinguished by a section of bleached tissue at the tissue margin (Table 1; Fig. 1F; Gil-Agudelo, Smith & Weil, 2006; Ritchie & Smith, 1998)

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