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 Panamá, in February (seawater temperature 20.7°C) and May (seawater temperature 28.5°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 mm diameter polyps) and Pavona gigantea (mounding morphology, 3.0 mm diameter polyps) were collected at 3 m, transplanted to 1 and 6 m 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 μm) 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.

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A geochemical proxy for surface ocean nutrient concentrations recorded in coral skeleton could provide new insight into the connections between sub-seasonal to centennial scale nutrient dynamics, ocean physics, and primary production in the past. Previous work showed that coralline P/Ca, a novel seawater phosphate proxy, varies synchronously with annual upwelling-driven cycles in surface water phosphate concentration. However, paired contemporaneous seawater phosphate time-series data, needed for rigorous calibration of the new proxy, were lacking. Here we present further development of the P/Ca proxy in Porites lutea and Montastrea sp. corals, showing that skeletal P/Ca in colonies from geographically distinct oceanic nutrient regimes is a linear function of seawater phosphate (PO 4 SW ) concentration. Further, high-resolution P/Ca records in multiple colonies of Pavona gigantea and Porites lobata corals grown at the same upwelling location in the Gulf of Panamá were strongly correlated to a contemporaneous time-series record of surface water PO 4 SW at this site (r 2 = 0.7-0.9). This study supports application of the following multi-colony calibration equations to down-core records from comparable upwelling sites, resulting in ±0.2 and ±0.1 lmol/kg uncertainties in PO 4 SW reconstructions from P. lobata and P. gigantea, respectively. P=Ca Porites lobata ðlmol=molÞ ¼ ð21:1 AE 2:4ÞPO 4 SW ðlmol=kgÞ þ ð14:3 AE 3:8Þ P=Ca Pavona gigantea ðlmol=molÞ ¼ ð29:2 AE 1:4ÞPO 4 SW ðlmol=kgÞ þ ð33:4 AE 2:7ÞInter-colony agreement in P/Ca response to PO 4 SW was good (±5-12% about mean calibration slope), suggesting that species-specific calibration slopes can be applied to new coral P/Ca records to reconstruct past changes in surface ocean phosphate. However, offsets in the y-intercepts of calibration regressions among co-located individuals and taxa suggest that biologically-regulated "vital effects" and/or skeletal extension rate may also affect skeletal P incorporation. Quantification of the effect of skeletal extension rate on P/Ca could lead to corrected calibration equations and improved inter-colony P/ Ca agreement. Nevertheless, the efficacy of the P/Ca proxy is thus supported by both broad scale correlation to mean surface water phosphate and regional calibration against documented local seawater phosphate variations.

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