Quantifying Coral Live Tissue Cover at Cano Island, Costa Rica

Quantifying Coral Live Tissue Cover at Cano Island, Costa Rica

Alvin Sherman Library

Coral reefs are essential marine ecosystems, serving as a reservoir of biodiversity while providing habitat and nourishment for associated benthic and demersal species. This research quantifies scleractinian coral live tissue cover at Caño Island, Costa Rica. Two study sites encompassing 225m², one shallow (4m depth) and one deep (11m depth), were each surveyed in January 2024 using GoPro Hero 11 cameras. Two photomosaics were created from several thousand smaller images (3,644 shallow and 3,888 deep) using AgisoftMetashape. Live coral tissue area was calculated using TagLab, documenting 53.09 m² and 58.16 m² in the shallow and deep sites respectively. This is equivalent to 23.6% (shallow) and 25.8% (deep) live coral cover. Pocillopora was only present in the shallow site where it composed 13.75% of the total coral live tissue cover, and Porites composed the balance of area (86.25%) in the shallow site and 100% of the area in the deep site. Although coral live tissue area was similar at the two depths, the shallower site had more colonies each with smaller surface area compared to the deep site that had fewer colonies, each with larger surface area. These live coral cover data were slightly higher than those of Guzman and Cortes (1989) who reported values averaging 20.6% at 4m depth and 23.0% at 9.5m depth. This documents no loss in coral cover at this site after 39 years, a beacon of hope in an era of unprecedented global decrease in coral cover.