Fig. 1. Sampling of corals and the environment along reefs from the northern and central GBR.

Samples for genetic analysis of corals’ symbiotic communities included 1644 samples from individual coral colonies of A. hyacinthus, A. tenuis, and A. millepora (n = 1454) and sediments representing the environmental pool (n = 189) from 2003 to 2019. Twenty-six reefs were surveyed genetically and varied in their responses to bleaching in 2016 (circles) and 2017 (triangles). The deviance in the maximum degree heating week (mDHW) residual (red to blue) between the accumulated heat stress measured in DHWs and the aerial survey bleaching response is shown per reef surveyed.