54.1 Saturday, Jan. 5 Coral-macroalgae dominance shift may impact flow-mediated recovery from bleaching RIPPE, J.*; STOCKING, J.; REIDENBACH, M.; University of Virginia, Charlottesville; University of Virginia, Charlottesville; University of Virginia, Charlottesville email@example.com
In the last decade, coral bleaching has emerged as one of the most pressing issues facing tropical coral reef ecosystems, a process that frequently results in a community dominance shift on the reef from a coral- to macroalgae-dominated system. Recent studies have shown that increased water flow enhances recovery from bleaching by reducing the boundary layer thickness and increasing mass flux between the coral and water column. We characterized the water flow profile and oxygen concentration immediately over the surface of both a healthy, coral-dominated and a bleached, algal-dominated specimen of Siderastrea siderea, by utilizing a Nortek Vectrino II velocimeter, particle image velocimetry, and an oxygen microelectrode. We coupled this to photosynthetic yield of the coral using in-situ pulse amplitude-modulated fluorometry. With this experimental setup, we quantified a significant effect on momentum boundary layer thickness over the coral due to macroalgal presence, which influenced oxygen flux at the coral surface-water interface and altered photosynthetic activity compared to healthy coral. As bleaching is often attributed to photorespiration and oxidative stress on the coral host, these results will likely have implications for recovery potential from a bleaching event.