Identifying Causes of Temporal Changes in Acropora cervicornis Populations and the Potential for Recovery

Abstract

Corals, specifically the Atlantic staghorn coral, Acropora cervicornis, are under major threat as disturbance events such as storms and disease and predation outbreaks increase in frequency. Since its population declines due to a wide spread disease event in the early 1980s, limited long-term monitoring studies describing the impact of current threats and potential recovery have been completed. The aim of this study was to document the impacts of environmental (tropical storms, increased wind) and biological (disease and predation) threats on A. cervicornis to further understand its population dynamics and potential for recovery. Two high-density A. cervicornis patches (greater than 1 hectare each) were surveyed tri-annually (winter, summer, fall) from 2008-2016. A. cervicornis percent cover, canopy height, census of individuals, and prevalence and occurrence of disease, predation, and bleaching were evaluated within permanent 3.5 m radial plots (n = 27 and 31). Temporal variability was observed in mean percent live cover at both patches and showed an overall loss of tissue. Frequent disturbances such as tropical storms, hurricanes, and disease events, caused increased, prolonged, and widespread mortality. Periods void of disturbance allowed for recovery and growth. Prevalence and occurrence of disease and predation were highly variable between monitoring events. They were also found to be significantly higher on masses (individuals ≥ 1.5 m) than on colonies and during summer surveys (June-August). These data indicate that substantial length of time between major disturbance events is necessary for recovery and growth of this species. The implication of these results is that given the current rates of growth, recruitment, and storm frequency, natural species recovery is unlikely unless large scale issues like climate change and ocean warming, which affect the intensity and frequency of disease and predation, are addressed.

Thermal stress-related spatiotemporal variations in high-latitude coral reef benthic communities

“…From late 2014, an unprecedented disease, termed stony coral tissue loss disease (SCTLD), spreads along the Florida Reef Tract (FRT), resulting in mortality of multiple species on the SEFRT, including key reef builders M. cavernosa, Meandrina meandrites and Siderastraea siderea (Walton et al 2018). Elevated disease prevalence during warm conditions has also been documented separately for A. cervicornis (Goergen et al 2019). The increased prevalence and susceptibility of corals to disease have previously been found to result from an increase in the duration of temperatures above the bleaching threshold (Bruno et al 2007).…”

Differential survival of nursery‐reared Acropora cervicornis outplants along the Florida reef tract

“…To facilitate the recovery of acroporid populations, coral restoration programs have expanded along the Florida reef tract over the last 15 years (Johnson et al 2011; Schopmeyer et al 2012; Young et al 2012). These restoration programs have focused particularly on restoring populations of A. cervicornis (Goergen et al 2019; Ware et al 2020). Although coral restoration may be a useful option to increase coral populations, strategies to optimize survival of nursery‐reared outplants are still in their infancy.…”

Survivorship and growth in staghorn coral (Acropora cervicornis) outplanting projects in the Florida Keys National Marine Sanctuary

“…Most colonies outplanted in the projects reported here exceeded this threshold at three years and exceeded 50% by four years. Various factors cause significant partial mortality including disease, predation by corallivores such as the gastropod Coralliophila abbreviata and the polychaete Hermodice carunctulata [28,96,97], and activity by damselfishes, chiefly Stegastes planifrons [92,98]. Identifying causes of mortality could be relevant to restoration success if they can be mitigated by interventions [99].…”