Microbial Community Dynamics Provide Evidence for Hypoxia during a Coral Reef Mortality Event
Shawn M. Doyle, Miabel J. Self, Joseph Hayes, Kathryn E. F. Shamberger, Adrienne M. S. Correa, Sarah W. Davies, Lory Z. Santiago-Vàzquez, Jason B. Sylvan
Abstract
In the northwestern Gulf of Mexico in July 2016, ∼82% of corals in a small area of the East Flower Garden Bank coral reef suddenly died without warning. Oxygen depletion is believed to have been the cause. However, there was considerable uncertainty, as no oxygen data were available from the time of the event. Microbes are sensitive to changes in oxygen and can be used as bioindicators of oxygen loss. In this study, we analyze microbial communities in water samples collected over several years at the Flower Garden Banks, including shortly after the mortality event. Our findings indicate that compared to normal conditions, oxygen depletion was widespread in the deep-water layer during the mortality event. Hydrographic analysis of water masses further revealed some of this low-oxygen water likely upwelled onto the coral reef.