Effects of upwelling, depth, morphology and polyp size on feeding in three species of Panamanian corals

We examined the effects of upwelling, depth, morphology and polyp size on coral feeding in 3 coral species in the eastern Pacific. Feeding rates and the species composition of zooplankton captured by these species were observed in situ on a shallow patch reef at Isla Contadora, Gulf of Panama, in February (seawater temperature 20.7 degrees C) and May (seawater temperature 28.5 degrees C) 2003 at 1 and 6 m depths. Fragments of the corals Pocillopora damicornis (branching morphology, 1.0 mm diameter polyps), Pavona clavus (mounding morphology, 1.3 rum diameter polyps) and Pavona gigantea (mounding morphology, 3.0 mm diameter polyps) were collected at 3 m, transplanted to 1 and 6 rn depth on the reef, placed inside feeding chambers, and exposed to high concentrations of natural zooplankton. After feeding, coral fragments were collected, the number and type of zooplankton within 100 polyps of each counted, and feeding rates calculated cm(-2). Feeding rates increased with increasing depth, were lower during periods of upwelling, and were higher in corals with mounding morphology than in those with branching morphology. Feeding rates cm(-2) did not vary with polyp size. Assemblages of captured zooplankton did not change with upwelling, depth, morphology or polyp size. The proportionate contributions of poor-swimming and mid-sized (200 to 400 pm) zooplankton taxa eaten were over-represented relative to their abundance. When combined with prior studies, these results suggest that coral feeding rates are facultative and that feeding rates vary due to increased feeding effort and not necessarily due to increased colony morphology or polyp size.