The Pulley Ridge deep reef is not a stable refugia through time

The deep reef refugia hypothesis (DRRH) suggests that mesophotic coral ecosystems (MCEs) represent a sanctuary for various coral reef taxa from impacts of natural and anthropogenic stressors. The Pulley Ridge FL mesophotic reef was surveyed using unmanned vehicles and technical diving in 2015 and compared to vehicle surveys in 2003, to test the DRRH. The MCE sites surveyed consisted of at least 25 species of algae (similar to 50% cover), 18 species of scleractinian corals (< 1% cover), 67 species of sponges (1-2% cover), in addition to 83 species of fish. The percent cover data indicate a significant decline of coral and sponges, and a significant increase in algae, relative to surveys conducted about a decade earlier. While the cause of this change is unknown, our results indicate that some mesophotic reefs may not be stable refugia for coral reef biodiversity and seed banks for resilience of damaged shallow reefs.