HI_Bleaching_Timeseries

Coral bleaching has become increasingly common on reefs worldwide as rising sea surface temperatures associated with climate change disrupt the coral-algal symbiosis. This dramatic heat stress response turns the normally colorful corals bright white, and yet during these heat stress events not all corals undergo bleaching. The physiological costs of symbiont loss are substantial, and even though both bleached and unbleached phenotypes are experiencing heat stress during a heatwave, bleached corals experience reduced survival relative to non-bleached conspecifics. Here we investigate the effects of repeated heat stress events on the performance of the Hawaiian corals Montipora capitata and Porites compressa, dominant reef builders throughout Hawaiʻi. These paired colonies of with bleached vs. unbleached histories have been monitored through two past bleaching events in Hawaiʻi (2015 and 2019) and the currently ongoing 2020 warming event. 10 pairs of Montipora capitata and Porites compressa colonies were assessed every 1-2 months as travel and COVID restrctions allowed. Corals were photographed and samples were collected for both molecular biopsies and physiological assays.