About weekly, bottle samples were also collected for total alkalinity and pH. Bottles were rinsed with sample repeatedly before sample collection. Alkalinity samples were collected in borosilicate glass bottles without air space, and were analyzed via a modified Gran titration using an 877 Titrino plus, typically within 3 hr of collection, though they appeared to be stable for at least 7 days. Titrations were verified using Certified Reference Materials obtained from Andrew Dickson and precision and accuracy were typically +-10 ueq/kg or better. pH samples were collected in 50 ml centrifuge tubes without air space and analyzed spectrophotometrically with m-cresol purple, following standard protocols, and typically within 1 hr of collection, though they appeared to be stable for at least 24 hr. Precision of pH analyses was typically +-0.002 units or better, while accuracy of this method is estimated as +-0.02 units or better.

Tank treatments:

Below, "High" or "Low" pH refers to target pH levels. "Fed" or "Unfed" refers to whether the tank was fed zooplankton not.

Tank t1: High pH, Unfed
Tank t2: High pH, Fed
Tank t3: Low pH, Unfed
Tank t4: Low pH, Fed
Tank t5: High pH, Fed
Tank t6: Low pH, Unfed
Tank t7: Low pH, Fed
Tank t8: High pH, Unfed

Location information:

​The coral collection sites were the reef around HIMB and the reef adjacent to Kaiona Beach Park in Waimanalo (about 1 mile north of the Makai Pier). The lat/long for the approximate center of the sampling area at each site are as follows, and the sampling at each site was located within about +/- 200 m of that central point:

Kane'ohe Bay: 21.4336 N, -157.7861 W
Waimanalo Bay: 21.3272 N, -157.6811 W

The tank experiments were conducted at the Point Lab on Coconut Island, which is ~18 km from the sampling area in Waimanalo Bay and adjacent to the sampling area in Kane'ohe Bay. The high pH treatment was ambient Kane'ohe Bay seawater chemistry (pH ~7.9-8.0) whereas the target for the low pH treatment was ~0.25 units below ambient.