Impacts of Stony Coral Tissue Loss Disease (SCTLD) on Coral Community Structure at an Inshore Patch Reef of the Upper Florida Keys Using Photomosaics

Graham Kolodziej,Michael S Studivan,Derek P Manzello,Ian C Enochs,Arthur C R Gleason,Chris Langdon

doi:10.3389/fmars.2021.682163

Abstract

Since the appearance of stony coral tissue loss disease (SCTLD) on reefs off Miami in 2014, this unprecedented outbreak has spread across the entirety of Florida’s coral reef tract, as well as to many territories throughout the Caribbean. The endemic zone reached the upper Florida Keys by 2016, resulting in partial or complete mortality of coral colonies across numerous species. Disease was first observed at Cheeca Rocks (Islamorada, Florida) in the beginning of 2018, with reports of coral mortality peaking mid-year. The disease was still present at Cheeca Rocks as of March 2020, however, to a lesser degree compared to the initial outbreak. Annual monitoring efforts have been ongoing at Cheeca Rocks since 2012, including repeated benthic photomosaics of a 330 m2 survey zone, spanning six replicate sites. As such, a repository of coral community composition data exists for before and after the disease outbreak that was analyzed to assess the impacts of SCTLD on reef communities at an upper Florida Keys inshore reef. Cheeca Rocks is hypothesized to be a resilient reef due to its persistent high coral cover despite its inshore location, which subjects corals to fluctuating water quality and marginal environmental conditions. Coral populations here have been shown to recover from bleaching events and heat stress with minimal coral mortality. Though colonies of coral species characterized as highly and moderately susceptible to SCTLD (e.g., Colpophyllia natans, Diploria labyrinthiformis, Pseudodiploria strigosa, Orbicella annularis, and O. faveolata) suffered mortality as a result of the outbreak with an average loss of 16.42% relative cover by species, the overall impacts on coral cover and community structure were relatively low, contributing to a loss of total coral cover of only 1.65%. Comparison of photomosaic data to other studies indicate Cheeca Rocks may not have been affected as severely as other sites on Florida’s coral reef tract, underlying this site’s potential role in coral resilience to stressors including bleaching events, land-based pollution, and disease epizootics.

Highlights

Florida’s coral reef tract has seen near-continuous declines in coral cover since at least the late 1970’s, starting with a disease event affecting two key habitat-building coral species, Acropora cervicornis and Acropora palmata (Aronson and Precht, 2001), followed by precipitous population declines of a key herbivore, the urchin species Diadema antillarum (Mumby, 2006; Mumby et al, 2007)
The disease was discovered to affect a wide variety of scleractinian coral taxa spanning multiple genera and families, unlike previously known diseases which were largely species- or genus-specific (Precht et al, 2016; Rippe et al, 2018; Walton et al, 2018; Aeby et al, 2019; Alvarez-Filip et al, 2019). Due to this aggressive nature of rapid and high mortality, as well as its virulence across numerous species, it was characterized as a novel disease named stony coral tissue loss disease (SCTLD; NOAA, 2018)
A total of 2,251 colonies from 17 coral species were identified in the 2017 mosaic plots, while 2,197 live colonies remained in 2019, indicating mortality of 54 colonies between years due to SCTLD (Table 1)

Summary

Introduction

Florida’s coral reef tract has seen near-continuous declines in coral cover since at least the late 1970’s, starting with a disease event affecting two key habitat-building coral species, Acropora cervicornis and Acropora palmata (Aronson and Precht, 2001), followed by precipitous population declines of a key herbivore, the urchin species Diadema antillarum (Mumby, 2006; Mumby et al, 2007). The disease was discovered to affect a wide variety of scleractinian coral taxa spanning multiple genera and families, unlike previously known diseases which were largely species- or genus-specific (Precht et al, 2016; Rippe et al, 2018; Walton et al, 2018; Aeby et al, 2019; Alvarez-Filip et al, 2019) Due to this aggressive nature of rapid and high mortality, as well as its virulence across numerous species, it was characterized as a novel disease named stony coral tissue loss disease (SCTLD; NOAA, 2018). The endemic zone spread rapidly throughout Florida’s coral reef tract, reaching Broward County to the north and Biscayne National Park to the south in 2015; Palm Beach County and the upper Keys in 2016; Martin County and the middle Keys by 2017; and continuing to reach the lower Keys by 2018 and 2019 (NOAA, 2018; Sharp et al, 2020), and the Dry Tortugas in 2021 (Roth et al, 2020)

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