QUANTIFYING THE IMPACTS OF EL NIñO ON ACROPORA CERVICORNIS ABUNDANCE AT CORAL GARDENS, BELIZE

In recent decades, coral reef mortality has been increasingly high, putting many species at risk of extinction. Among these is the coral Acropora cervicornis (Staghorn Coral) that historically has acted as a framework coral and keystone species for Caribbean reefs. Declining live coral cover has been attributed to disease, warming ocean temperatures, eutrophication, overfishing, and natural sub-decadal climate cycles such as El Niño. The 2015-16 El Niño event has been one of the strongest in recorded history, leading scientists to project significant coral mortality via heat-induced bleaching in the Caribbean and elsewhere. Coral Gardens, Belize is noted for having high live A. cervicornis cover. This study aims to quantify changes in coral cover in an area of previously documented high A. cervicornis resilience, over the latest El Niño cycle and earlier. We photographed and digitized 133 m² quadrats along five transects at Coral Gardens to measure 2D percent live coral cover in summer 2016 and in past years. We also collected temperature measurements from data loggers at 30-minute intervals over the past four years. From June 2015 – June 2016 mean annual temperature increased about 0.8 degrees F over past years. Spikes in daily temperature were more frequent and higher amplitude, and anomalously high temperatures lasted longer in this most recent El Nino cycle. Live coral cover data show net loss in live A. cervicornis cover from 2011-2016 along each transect and 99% of quadrats analyzed to date. Mean coral cover for the transect with the highest live coral decreased from 59.8% in 2012 to 51.7% in 2014 and 35.5% in 2016. In areas of less abundant live A. cervicornis, live coral decreased from an average of 14.3% to 13% in two years. The recent history of frequent temperature spikes and sustained high temperatures likely caused the observed dramatic live coral loss. This loss of live coral at Coral Gardens is especially concerning given the site’s history as a refuge for A. cervicornis.