Per polyp feeding rate was independent of the horizontal planform area of colonies. At the lowest velocities, most particles were captured on the upstream edge or in the middle of colonies, but all positional bias in capture rate disappeared at higher velocities. Particle capture and increasing flow speed were negatively associated. There were small, but measurable, differences in mean tentacle length between corals feeding at different velocities. Velocity-dependent feeding rate at most velocities was thus related to changes in flow rather than to changes in feeding behavior. Experiments in which corals were turned upside down revealed that the increased capture rate for rightside-up corals feeding at low velocity could be almost entirely accounted for by gravitational deposition of particles on the corals' tentacles. The tentacles form a canopy within which water movement was slowed, possibly facilitating gravitational deposition of non-buoyant or sinking food particles. -from Authors
Johnson, A. S. and Sebens, K. P., "Consequences of a flattened morphology: effects of flow on feeding rates of the scleractinian coral Meandrina meandrites" (1993). Biology Faculty Publications. 154.