Ecological consequences of Stony Coral Tissue Loss Disease in the Turks and Caicos Islands

Abstract

Coral reefs are suffering global declines due to climate change, natural disasters, pollution, and diseases. Coral disease events have increased in frequency and severity in the past several decades and have nearly wiped out populations of some Caribbean coral species. Stony coral tissue loss disease (SCTLD) is a novel white plague that infects many species, is highly contagious, and causes rapid mortality. SCTLD was first documented in the Turks and Caicos Islands in 2019. This study described the trends in coral community composition, cover, richness, and diversity from 2012 to 2020 on the South Caicos fore reef, to contextualize the impact of the ongoing disease outbreak in 2020. Monitoring sites were assessed using photo quadrats along permanent transects and CPCe for analysis. Coral cover, richness, and diversity remained consistent from 2012 to 2018. Coral cover was significantly lower in 2020 after the outbreak (1.14% ± 0.65) than in any other year (2.97% ± 1.12%, mean 2012–2018), a 62% loss. Richness reached its lowest point and was significantly lower in 2020 (6.33 ± 1.37 taxa) than in all other years except for 2013 and 2016, and diversity reached its lowest point in 2020 as well. Coral community composition differed by year and particularly in 2020, with significant differences between 2013/2014 and 2020. In 2020, rare and susceptible taxa Dichocoenia spp., Eusmilia fastigiata, and Meandrina meandrites were absent from all surveys for the first time. Trends in relative cover of “weedy” coral taxa varied, with Agaricia spp. reaching its lowest relative cover (24.2%) in 2020 and Porites astreoides reaching its highest (18.9%). Ecological shifts associated with SCTLD in South Caicos are the first reported in the Turks and Caicos Islands and support other studies in the Caribbean which demonstrate that SCTLD significantly deteriorates reef composition.