4.1 Physiological Adaptation of Turbinaria peltata to
marine heatwaves
Recent studies have provided increasing evidence for the adaptive
capacity of corals to heat stress (Yu et al., 2020; Hackerott et al.,
2021; Schoepf et al., 2022). This adaptability primarily relies on the
thermal tolerance of their symbiotic algae, with susceptible populations
being expelled while those remaining show enhanced metabolic activity
and photosynthetic efficiency to cope with high temperatures (Perniceet
al., 2012; Arandia-Gorostidi et al., 2017; Stanley and van de
Schootbrugge, 2018). In our study, the initial exposure to MHWs resulted
in a significant decrease in the density of diatoms (p <
0.05). However, the second exposure to MHWs provided relief from this
impact. Furthermore, corals regulate the synthesis and activity of
antioxidant enzymes, such as superoxide SOD, CAT, and GST, as well as
apoptotic proteases like Caspase-3, to counteract acute heat stress
(Bhagooli and Hidaka, 2004; Lesser, 2006; Thummasan et al., 2021). The
initial exposure to MHWs led to a significant increase (p <
0.05) in the levels of GST, Caspase-3, SOD, and CAT. However, the
effects were alleviated upon subsequent exposure to MHWs. This
regulatory process helps in clearing excessive reactive oxygen species
(ROS), thereby maintaining normal cellular function and physiological
state. Consequently, repetitive exposure to heatwaves imposes less
physiological stress on corals compared to their initial exposure (Xu et
al., 2021), indicating potential physiological adaptations ofTurbinaria peltata to withstand MHWs.