Methods reprinted from Barkley et al. 2017:
\nCoral collection:\u00a0Coral plugs were collected in December 2012 from massive Porites colonies at a naturally low-\u03a9ar reef site (7.324 N, 134.493 E; mean \u03a9ar = 2.3; n = 78) and a naturally high-\u03a9ar reef site (7.268 N, 134.522 E; mean \u03a9ar = 3.7; n = 75). At each reef site, small skeletal cores (diameter = 3.5 cm) were removed from massive colonies (one core per colony) at 2-3m depth using underwater pneumatic drills, and cores were cut with a lapidary table saw to approximately 1 cm below the tissue layer. The plugs were affixed to nylon square base screws with marine epoxy, secured to egg crate racks, and returned to their original reefs to allow the corals to recover from the coring procedure. All corals survived two months of recovery on the reef and on all corals living tissue had fully overgrown the sides of the plugs so that no underlying skeleton was exposed. Corals were recovered in February 2013.
Reciprocal transplant experiment:\u00a0The reciprocal transplant experiment was conducted concurrently with the CO2 manipulation experiment. Initial buoyant weight measurements were obtained for all corals prior to transplantation. Of the corals collected from the low-\u03a9ar reef and from the high-\u03a9ar reef (n = 44 for each reef), approximately half of the corals in each group was returned to their reef of origin (low-\u03a9ar to low-\u03a9ar: n = 23, high-\u03a9ar to high-\u03a9ar: n = 21), while the remaining corals were transplanted to the opposite reef (low-\u03a9ar to high-\u03a9ar: n = 21, high-\u03a9ar to low-\u03a9ar: n = 23). All corals were transplanted to the same depth (5m). In May 2013, after eight weeks in the field (and at the end of the CO2 manipulation experiment), approximately half of the corals from each reef (n = 10-12 per transplant group) were recovered and weighed. The remaining corals were left out on the two reefs for 17 months (n = 10-11 per group). In August 2014, these corals were recovered from the reef.\u00a0Corals were evaluated for partial or total mortality, and were judged to be alive (no visible tissue death observed), partially dead (visible tissue death and/or tissue recession but some living tissue remaining), or dead (no living tissue remaining). Buoyant weights were collected for all corals to determine overall calcification rates during the reciprocal transplant period. Because coral tissue is assumed to be neutrally buoyant (i.e. it does not contribute to buoyant weight measurements) and the timing of tissue death during the 17-month transplant was unknown, the overall change in skeletal mass was calculated and reported for all corals regardless of mortality status.
Data from reciprocal transplant experiments on Palau Porites coral.
\nThese data were originally published in figures 4 and 5 of:
\nBarkley, H. C., Cohen, A. L., McCorkle, D. C., & Golbuu, Y. (2017). Mechanisms and thresholds for pH tolerance in Palau corals. Journal of Experimental Marine Biology and Ecology, 489, 7\u201314. doi:10.1016/j.jembe.2017.01.003
Parameter names have been modified to comply with BCO-DMO naming conventions.