CORAL GARDENS, BELIZE: QUANTIFYING ACROPORID CORAL SURVIVORS

Acropora spp. coral colonies emerged as the dominant framework-building corals in the Caribbean during the Pliocene Epoch and remained so through most of the Holocene. However, over the past four decades, acroporids have suffered up to 98% mortality due to multiple synergistic environmental factors. Despite this decline, Coral Gardens Reef, Ambergris Caye, Belize has been recognized as an ecological refugium for Acropora cervicornis. Our research evaluated patterns in live coral cover of A. cervicornis at Coral Gardens for 10 years (2012-2022). We photographed and analyzed ~140 1-m² quadrats per year along 5 previously established transects. Two new transects (59 1-m² quadrats) were surveyed in 2022 to establish a baseline for the abundance of the hybrid A. prolifera and for future monitoring efforts. We rectified images using Matlab, outlined live coral in each quadrat using Adobe Illustrator, and used a Matlab script to calculate percent live coral in each quadrat. Sea surface temperature (SST) was also measured at 15-minute to 1-hour intervals at Coral Gardens for 10 years using Onset HOBO temperature loggers, to explore the potential role of SST in annual abundance of Coral Gardens acroporids. The greatest loss of live coral occurred between 2016 and 2017 (p<0.05). During that time period, we recorded 57 temperature measurements that were >1 °C above the mean of the warmest month. However live coral abundance appeared to stabilize after 2018 (13.36% live) and even increased to an average cover of 20.23% in 2022. Between 2021 and June 2022, there was a statistically significant increase in average percent live cover (p<0.05), with Transect 5 increasing from 18.09% live coral in 2017 to 40.63% in 2022. Both bushy and palmate A. prolifera appear to be thriving at Coral Gardens. Although A. prolifera patches are smaller in size than those of A. cervicornis (6.7 m² versus 19.0 m² on average), percent live coral at the center of patches of both species is similar, with A. prolifera patches reaching up to 60% per m², and A. cervicornis reaching 62% live coral. While reefs in the Caribbean continue to decline, we find hope in the apparent stabilization of A. cervicornis and the presence of A. prolifera, which appears to be thriving at Coral Gardens.