Differing Responses of Three Scleractinian Corals from Phuket Coast in the Andaman Sea to Experimental Warming and Hypoxia

Abstract

An unprecedented decline in the diversity and health of coral reefs is occurring around the world as they are threatened by multiple global and local stressors. Rising seawater temperature and low dissolved oxygen (DO) conditions are expected to intensify as a result of climate change. Understanding the responses of corals to these stressors is necessary for making predictions and devising mitigation strategies. The three coral species—Porites lutea, Montipora tuberculosa, and Pocillopora verrucosa—were sampled from Patong Bay, Phuket, Thailand, as representatives of different coral morphologies. Coral nubbins were subjected to experimental investigation under ambient conditions (29 °C, DO > 6 mgL−1), heat stress (32 °C), hypoxia (DO < 2 mgL−1), and heat stress + hypoxia treatments. Photosynthetic performance indicators Fv/Fm and Fv/F0 and physiological parameters Symbiodiniaceae density, pigment concentration, and growth rate were quantified. We found P. verrucosa (branching) to be the most sensitive and severely affected by heat stress or hypoxia, more so than P. lutea (massive) and M. tuberculosa (tabular). The combination of these stressors had less impact on these species, except for a decline in growth rate of M. tuberculosa. This study also suggests that the corals respond differently to high temperature and low oxygen, with their sensitivity depending on species. These responses, however, may differ according to the lighting, especially in hypoxic conditions. The results fill a research gap to help predict the vulnerability of these three coral species in shallow reef habitats under climate change scenarios.

Natural thermal stress-hardening of corals through cold temperature pulses in the Thai Andaman Sea

“…and Porites sp. despite representing a naturally thermo-sensitive and a robust coral ecotype, respectively (Brown and Phongsuwan 2012;Schmidt et al 2012;Jain et al 2023). In the following we discuss these new insights about environmental priming, while considering the regional context of the Thai Andaman Sea, and with regard to designing efficient preconditioning treatments that can enhance coral thermal resistance for coral reef conservation.…”

“…were permanently tagged to assess their thermal resistance levels during the two seasons (n=8 to n=18, Figure 1 C, Table S1). These two coral species are cosmopolitan reef-builders in Thailand and within the entire Indo-Pacific region (Brown and Phongsuwan 2012;Schmidt et al 2012;Jain et al 2023). Coral fragments were collected at the end of April 2018, an episode of strongest internal wave impact, and at the end of October (Porites sp.)…”