Presenter: Heng Wu (Okinawa Institute of Science and Technology)

Description:
Transparent exopolymer particles, a form of coral mucus, are responsible for particle aggregation and formation of “marine snow.” This induced aggregation of biological particles from various sources is crucial to food webs and the carbon cycle, both for the reefs themselves and for surrounding marine environments. While prior studies have shown that water flows affect corals in many ways, direct evidence of feedback between flow characteristics (such as fluid shear) and the rate of transparent exopolymer particle release by corals has not been addressed.  In this study, we quantified potential effects of flows on transparent exopolymer particle release by corals and associated bacterial growth, using laboratory flume experiments. Coral colonies were placed in a recirculating flume and exposed to unidirectional flows. Changes in concentrations of transparent exopolymer particles and bacteria were evaluated during 24 hours of incubation. Two-dimensional, two-component particle image velocimetry (PIV) was used to measure the flow field around and above the coral colonies. With these flow field measurements, fluid shear and turbulence intensity were estimated and used to evaluate the effect of flow on transparent exopolymer particle release by corals.