THE EFFECTS OF FLOW ON FEEDING OF 3 GORGONIANS FROM SOUTHERN TAIWAN

The feeding performances of three gorgonians, Subergorgia suberosa, Melithaea ochracea. Acanthogorgia vegae, in different flow regimes were studied. The three gorgonians expanded their polyps and fed in varying ranges of flow velocities. Differences in the feeding range are possibly related to polyp morphologies. S. suberosa, which has tall polyps and encounters higher drag, is more easily deformed in currents; it feeds in a narrow range of flow velocities (7-9 cm.s(-1)). M. ochracea, which has short polyps and encounters lower drag, is less readily deformed in currents; it feeds in a wider range of flow velocities (4-40 cm.s(-1)). Polyp heights of A. vegae are intermediate and this coral feeds in currents of 2-22 cm.s(-1). The upper limits on the flow ranges are considered to be determined by the balance between the energy gained from feeding and the cost of keeping the polyps expanded. Optimal feeding rates of the three gorgonians were found at moderate flow velocities. Feeding rates increased initially with flow velocity, reached a peak value at 8 cm.s(-1), then decreased with increasing flow velocities. Both the colony feeding effectiveness and the polyp feeding effectiveness at 8 cm.s(-1) are ranked: S. suberosa>A. vegae>M. ochracea.