Figure 2.

Summary of coral heat stress responses. Increasing temperatures trigger calcium release from the endoplasmic reticulum, which leads to various changes in cell function (e.g., cytoskeleton rearrangement, cell adhesion disruption) through disruption of calcium homeostasis. Meanwhile, the metabolic rate is also increased, causing an increase not only in reactive oxygen species (ROS) but also in nitric oxide (NO). Consequently, oxidative stress from ROS and NO is experienced by the coral, which can ultimately lead to apoptosis or necrosis. Symbiodiniaceae have their own temperature tolerance and responses but also produce ROS under stress, which can leak into the host and exacerbate oxidative stress