Meeting Abstract

7.4  Friday, Jan. 4  Boundary layer flow effects on dissolved oxygen exchange and photosynthesis in scleractinic corals STOCKING, J.B.*; RIPPE, J.P.; REIDENBACH, M.A.; University of Virginia jbs4yq@virginia.edu

To investigate the interaction between flow environment and coral photosynthesis, in-situ field measurements of boundary layer flow, photosynthetic quantum yield, and dissolved oxygen levels were obtained over the scleractinic corals Porites furcata and Siderastrea siderea in the coastal ocean of Bocas del Toro, Panama. A vertical profile of three-dimensional velocity structure was obtained using a high-resolution profiling acoustic Doppler velocimeter. Estimates of Reynolds stress, turbulent kinetic energy, and wave orbital motion were derived from these velocity measurements. Local rates of coral photosynthesis were measured using a pulse-amplitude modulated (PAM) underwater fluorometer, and dissolved oxygen (DO) concentrations were measured at the same location using a fluorescence-based optical needle probe. Results show that periods of higher root-mean square (RMS) velocity in the free water column correlate to higher maxima of turbulent kinetic energy (TKE) in the momentum boundary layer directly above the coral-water interface. Larger TKE values also correlate with higher levels of photosynthetic quantum yield and with increases in dissolved oxygen concentration at the coral-water interface. The combined measurements suggest that turbulent eddies act to break down the diffusional boundary layer at the coral surface, thereby promoting DO exchange out of the coral polyp and driving the reaction kinetics of photosynthesis. The results provide in-situ evidence for flow-induced physical control over coral physiology and for consideration of flow as a key parameter in coral health.