Photochemical yield and color score data from short-term heat stress assays performed with with corals collected from sites around Heron Island, southern Great Barrier Reef in Sept and Oct of 2022

Variable temperature regimes that expose corals to sub-lethal heat stress have been recognized as a mechanism to increase coral thermal tolerance and lessen coral bleaching. However, there is a need to better understand which thermal regimes maximize coral stress hardening. Here, standardized thermal stress assays were used to determine the relative thermal tolerance of three divergent genera of corals (Acropora, Pocillopora, Porites) originating from six reef sites representing an increasing gradient of annual mean diel temperature fluctuations of 1–3°C day-1. Bleaching severity and dark-acclimated photochemical yield (i.e., Fv/Fm) were quantified following exposure to five temperature treatments ranging from 23.0 to 36.3°C (see Related Datasets for temperature data). This data set contains photochemical yield and color score data used to determine effective dose 50 (ED50, thermal tolerance). It also includes images used for analysis of coral color, a proxy for bleaching severity.