Standard Presentation Australian Marine Sciences Association Annual Meeting 2023

Quantifying legacy effects of thermal stress on coral growth  (#41)

Isabella A Marrable 1 , Mariana Alvarez-Noriega 1 , Juan C Ortiz 1
  1. The Australian Institute of Marine Science and The University of Sydney, North Ward, QLD, Australia

As temperature abnormalities intensify in frequency and severity, understanding coral thermal stress responses and their legacy becomes increasingly critical for predicting future population trajectories. Sudden or prolonged thermal stress requires organisms to rapidly adjust their physiology to compensate for an energetic deficit, which can affect fitness even after thermal stress eases. We refer to coral thermal legacy effects as the ongoing metabolic depression of key life history traits caused by previous exposure to unfavourable conditions.  In this study, we quantified the legacy effect on coral growth following chronic thermal stress. We exposed coral fragments from five common species to temperatures ranging from 19 to 31°C for one month to produce a gradient of thermal stress. Then, we moved fragments to tanks set at 26.5°C and monitored their growth for two months to investigate the legacy effect from their previous thermal history. Our findings suggest that the growth of coral colonies may exhibit prolonged impairment through metabolic depression as a result of their previous thermal stress history, but that the effects are species-specific. A prolonged reduction in coral growth following thermal disturbance has implications for broadscale ecosystem recovery and the structural landscape that underpins sites of high biodiversity.