The Pulley Ridge deep reef is not a stable refugia through time
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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 (~ 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.
KeywordsAlgae Corals Deep reef refugia hypothesis Mesophotic coral ecosystem Sponges Temporal variation
We thank E. Kintzing and J. Godfrey for help on our deep technical dives, A. Diercks and R. Jarnagin for assistance with the AUV and ROV operations, and J. Ambrose and J. McClure for assistance with the construction of the AUV Ulithi. The crew of the R/V Pelican was exceptionally helpful in providing logistics, as was the staff of the US Park Service-Dry Tortugas. All research conducted for this project complied with laws of the USA, under permits granted by the State of Florida. This research was funded by a Grant from NOAA’s Ocean Exploration and Research to M Slattery.
Compliance with ethical standards
Conflict of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
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