Poster Australian Marine Sciences Association 2022

The influence of heat stress protocols on resolving thermal sensitivity of Symbiodiniaceae (#489)

NATASHA BARTELS 1 , Nicole Dilernia 1 , Emma Camp 1 , David Suggett 1
  1. University of Technology Sydney, ULTIMO, NSW, Australia

Unlocking the mechanisms by which Symbiodiniaceae regulate their hosts’ bleaching susceptibility has been the focus of heat stress studies for over 30 years. Past experiments on Symbiodiniaceae isolates have focused on primarily acute heat stress with very few long-term studies, but how the data collected across different heating protocols can be reconciled remains unknown. We determined whether decreasing the rate of heating (from more to less acute) would result in the same photophysiological response across Symbiodiniaceae taxa. Cultures of various taxa were subjected to a series of treatments with different rates of thermal ramping, spanning from instantaneous heating to 1°C/3 days, increasing from 26°C to 32°C. Heating commonly induced decreases in maximum photochemical efficiency (Fv/Fm) though the rate at which these changes occurred was variable between strains. The suite of thermal protocols used across taxa demonstrated that: i) different ramping rates elicit stress responses of varying intensity ii) for Breviolum sp. and Durisdinium sp., decreasing Fv/Fm was generally observed with increasing length of the ramping period, and iii) the relationship between ramping rate and photophysiology was variable across strains. We discuss how these outcomes potentially impact our capacity to integrate responses observed from past experiments.