POTENTIAL IMPACTS OF ACROPORA CERVICORNIS MORTALITY ON CARBONATE PRODUCTION AND SEQUESTRATION AT CORAL GARDENS, BELIZE

In 2020, Coral Gardens Belize was identified as a refugium for Acropora cervicornis (Staghorn coral), highlighting the resilience of this endangered species at this site. However, the reef suffered total collapse during the 2023 marine heatwave, with live coral cover dropping from ~30% to 0%. This study examines how the mortality of A. cervicornis might affect carbonate production at Coral Gardens and the potential impacts on future carbon sequestration at the site. At the reef scale, we first attempt to quantify the volume of coral carbonate present at one location (T5) using bathymetry data from depth gauges, 3D software Global Mapper, Agisoft Metashape and Reality Capture, and GoPro video data from Coral Gardens. In 2023, the T5 reef measured approximately 40 m by 25 m in length and width, with a maximum coral height of 2.1 m above substrate. Assuming the reef is approximately half an ellipsoid (dome shaped), it would occupy a volume of 1,100 cubic meters. We are in the process of estimating the ratio of coral carbonate to void volume within the reef architecture. At the individual coral scale, we quantified 3D coral growth parameters (linear growth, volume, and surface area) of 4 living A. cervicornis specimens outplanted at Silks Caye, Southern Belize. We used Agisoft Metashape 3D software and Cinema 4D to estimate the volume of carbonate that living A. cervicornis produce annually. We assessed postmortem bioerosion and encrustation of coral in December 2023, June 2024, and December 2024 using 3D photogrammetry and dissection techniques to estimate changes in carbonate vs. pore volume in postmortem coral. Bathymetry and reef volume estimates establish a baseline for future monitoring of carbonate levels and interstitial habitats for reef organisms at this site. The outplanted living coral specimens increased in maximum length by 94-111% of original length, grew 3 to 9 additional branches, and expanded in volume by approximately 147-295% of original volume between June 2023 and June 2024. Preliminary analyses indicate that coralline algal colonization of postmortem A. cervicornis was rapid, suggesting an initial increase in carbonate accumulation by opportunistic non-coral carbonate producers, and we are in the process of quantifying the impacts of bioerosion of coral carbonate at the site.