Collection and experimental setup methods extracted from Doo et al. (2018):
Colony collection: In January 2017, 48 colonies of Pocillopora verrucosa (Ellis and Solander 1786) were collected randomly on scuba from 5 m depth on the north shore of Mo’orea, French Polynesia (17° 28' 33"S, 149° 49' 20"W). Following 5 d of acclimation, 24 of the corals were selected randomly for removal of all trapeziid crabs and alpheid shrimps ("minus-ectosymbiont") by probing with a wooden stick (3 mm diameter). Crabs and shrimp were left in the other 24 corals ("plus-ectosymbiont"), which were subjected to a procedural control in which they were probed with a wooden stick.

Incubation setup: Twelve mesocosm tanks (150 L volume with sand-filtered seawater pumped from 14 m depth in Cooks’ Bay and supplied to the tanks at ~200 mL min−1) were used in this experiment, with four colonies per tank in a split-plot design contrasting plus-ectosymbiont (n = 2 colonies/tank) and minus-ectosymbiont (n = 2 colonies/tank) corals.

Daily measures of salinity, pH, and total alkalinity (TA):
Temperature was recorded with a thermometer (± 0.05 degrees C; ThermoFisher Traceable) and salinity was measured with a bench-top conductivity meter (± 0.1 psu, YSI 3100). TA and pH were measured within one hour of sample collection. Seawater collected for TA was filtered (0.45 um; Chanson and Millero, 2007) and analyzed using potentiometric titrations with 0.1-N HCl using an automatic titrator (Mettler Toledo T50) (Dickson et al., 2007). Seawater pH was measured with spectrophotometric methods (Nemzer and Dickson, 2005).