Standard Presentation (15 mins) Australian Marine Sciences Association 2022

Bleaching severity and colony size influence taxonomic bleaching susceptibility in scleractinian corals across Australia's Great Barrier Reef and Coral Sea Marine Parks (#101)

Deborah Burn 1 , Andrew S Hoey 1 , Samuel Matthews 1 , Hugo B Harrison 1 2 , Morgan S Pratchett 1
  1. ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia
  2. Australian Institute of Marine Science, Townsville, Queensland, Australia

Climate-induced coral bleaching represents one of the foremost threats to coral assemblages globally. Differential bleaching susceptibility and subsequent mortality, which can cause marked shifts in population and community structure, is likely to be dependent on overall bleaching severity. We examined variation in bleaching susceptibility of 20 common coral genera, comparing among five categories of bleaching severity and three colony size categories. This extensive study covered 33 reefs across the Great Barrier Reef and Coral Sea Marine Parks during mass-bleaching in February-March 2020. Whilst Stylophora, Goniastrea, and branching Acropora were consistently among the most bleached taxa, and Leptastrea and Lobophyllia the least bleached, the hierarchy of bleaching susceptibility among taxa changed with increasing bleaching severity. Furthermore, small (<5cm diameter) Stylophora, Goniastrea, massive Porites, Favites, Lobophyllia and Fungiidae colonies were significantly less likely to bleach than larger (5-40cm diameter) congenerics, whereas small Pocillopora and Montipora colonies bleached more often than larger colonies. These findings suggest that colony size, as well as bleaching severity, are important determinants of taxonomic bleaching susceptibility and should both be taken into account to ascertain likely shifts in the structure of coral assemblages with increasing incidence and/or severity of mass-bleaching.