Abstract
Coral heterotrophy has been studied for over a century, mainly focusing on the biological aspects of the feeding process. Due to the lack of physical studies, the fluid flows generated by corals to facilitate active feeding remain mostly a myste1y. Many coral species are known to be passive suspension feeders through their use of mucus to capture food. However, the extent to which corals actively suspension feed remains unknown until the fluid flows they generate are elucidated. Heterotrophy in corals makes up for the nutrients that their endosymbiotic algae cannot provide. This form of nutrition is important to maintaining healthy corals, but it's critical for bleached corals, which can meet up to 100% of their metabolic demands through heterotrophy. My thesis focuses on uncovering these coral feeding-flows and finding supp01t for a hypothesized suction flow in two local South Florida species of coral, Montastrea cavernosa (great star coral) and Pseudodiploria clivosa (knobby brain coral). I process simultaneous top view and side view videos of corals while they are resting and feeding to reveal the flow patterns of tracer microbeads in the water. Applying Flow trace and Manual Tracking to the 3D observations shows the paths of microbeads caught in the coral-generated surface flows.Processed videos reveal suction flow along with three other stereotypical flow patterns in resting corals and feeding corals. Therefore, we conclude that coral polyps manipulate the flow of water immediately sunounding them, and that this manipulation likely differs between resting and feeding periods. Our flow visualization results can be used to info1m future quantitative analysis of the feeding process. As conditions in the ocean deteriorate globally for corals, it's becoming even more urgent to understand the biophysical processes that maintain them through new perspectives; especially the active feeding that suppo1ts corals during bleaching.