Poster Australian Marine Sciences Association 2022

The Thermal Performance of Coral Endosymbionts Adapted to Different Reef Habitats  (#482)

Nicole J Dilernia 1 , David Suggett 1 , Emma Camp 1 , Natasha Bartels 1
  1. Future Reefs Research, University of Technology Sydney, Sydney, NSW, Australia

Cnidarian-Symbiodiniaceae relationships are central to the success of Scleractinia in tolerating stressors – particularly temperature-driven coral bleaching – shaping thermotolerance and capacity to adapt to ever-changing environmental conditions. Thermal Performance Curves (TPCs) can reveal how changing temperatures influence competitive fitness, and by developing a novel rapid assay we prepared TPCs of an array of genera of Symbiodiniaceae isolated from diverse habitats. Cultures were exposed to sequential temperature treatments, and photophysiology was measured via Light Induced Fluorescence Transient-Fast Repetition Rate fluorometry. Exposure to thermal anomalies outside the general tolerance range resulted in decreased maximum photochemical efficiency, decreased PSII effective absorption rate, and slower photochemical turnover. However, these observations varied across the isolates, revealing thermal “generalist” capabilities of a temperate species, and “specialist” capabilities of an isolate originating from a naturally extreme environment with increased temperature, low oxygen, and low pH regimes. Coupled with a meta-analysis to benchmark cultured Symbiodiniaceae studies from 1,400 published articles, our work is the first to compare thermal performance in this way, distinguishing differences in endosymbiont thermal optima and the extreme temperatures which restrict their thermal performance range, and uncovering differences in the parameterisation of alternate photophysiological measurements and their capabilities in capturing and describing thermal performance.