This dataset includes metabolic rates of the coral species Porites astreoides and Montastraea cavernosa from Bermuda that were exposed to a temperature reduction experiment for 37 days. Prior to the experiment, 8 corals were collected with a hammer and chisel on 16th June 2019 in 5 m depth at Sea Venture Shoals, Bermuda [32º22'53” N, 64º38'11” W], which is an exposed reef featuring a typical Bermuda reef community. Water temperature during collection was ~27°C. The seasonal temperature range of Bermuda reefs is ~19°C to 29°C. The laboratory-based experiment took place at the Bermuda Institute of Ocean Sciences from 1st July to 6th August 2019 and used flow-through seawater from the adjacent Reach. Light was provided by Indoor grow lights, Sun Blaze T5 Fluorescent 44. The successive treatments were: (i) constant control temperature at 28°C, and (ii) temperature reduction (0.5 °C/day) followed by constant temperature for 20 days at 24 °C and (iii) temperature reduction (0.5 °C/day) followed by constant temperature for 20 days at 20 °C. Metabolic rates were measured on day 1, 5, 9, 13, 17, 22, 26 and 37 of the experiment. Metabolic rates include photosynthesis and oxygen consumption rates measured by respirometry. Standardized to coral surface are net photosynthesis, respiration and gross photosynthesis. Metabolic rates were measured in 1 liter glass incubation chamber (kitchen ware) equipped with an oxygen sensor spot (OXSP5, PyroScience, Germany), a magnetic stirring bar, and a grid for coral placement above the stirring bar controlled by a magnetic stirring plate (LABOMAG Mulitpoint magnetic stirrer, SHP Steriltechnik, Germany). Light was supplied with aquarium lamps (PAR ∼210–240 μmol photons/m²/s; indoor grow light, Sun Blaze T5 Fluorescent 44). In addition, gross photosynthesis is standardized to zooxanthella cell, amount of light-harvesting/photo-collecting pigments and respiration is standardized to total biomass.

Sample IDs indicate species (M=Montastrea cavernosa, P= Porites astreoides), the replicate ID (1 to 8; each replicate is a different coral colony) and the fragment ID (A-G; each coral colony was divided into 7 fragments).