International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.6, 260-266 http://ecoevopublisher.com/index.php/ijmec 262 3 Coral Bleaching Patterns and Influencing Factors Under Heat Stress Conditions 3.1 Types and degrees of albinism Coral bleaching shows significant heterogeneity. Some corals are only slightly bleached, some have completely lost their symbiotic algae, and others die directly. Long-term studies have shown that individuals of the same coral species may exhibit different bleaching and recovery trajectories during repeated heat waves. For instance, some initially sensitive individuals showed adaptability after several heat waves - their bleaching decreased in subsequent heat waves (Brown et al., 2023). Some corals can still sustain their lives temporarily even if they lose most of their symbiotic algae. However, when the degree of albinism develops beyond the critical threshold, the energy gap becomes difficult to make up for and may eventually lead to large-scale deaths. 3.2 Influence of environmental factors Environmental conditions strongly affect how easily corals bleach. Heat-stress tools, such as NOAA’s Degree Heating Weeks (DHW), are often used to estimate bleaching risk. However, the usual DHW value cannot fully explain why different regions do not respond the same way (Whitaker and DeCarlo, 2024). Some studies show that places with large temperature swings or strong water mixing are not always safer. Bleaching can still happen in coral areas where the temperature changes a lot (Brown et al., 2022). Local factors also matter. Water flow, nutrients, and the amount of sediment can change how much light corals absorb, how much energy they need, and how much stress their cells face. For example, slow water flow can make heat stress even worse. In contrast, moderate water movement can help corals lose heat faster and spread out waste products, which may reduce stress. 3.3 Differences in coral species Different coral species show very different levels of heat tolerance. This variation comes from several factors, such as the coral’s own genes, the type of symbiotic algae they host, and the conditions they experienced in the past. For example, a transcriptome study showed that a type of Acropora coral from Ningaloo Island changed its gene activity very quickly when exposed to sudden heat stress at 33°C. Genes related to heat-shock proteins, ion transport, and immunity became adjusted during the stress period. The heat tolerance of the symbiotic algae (for example, different groups within Symbiodiniaceae) also affects how fast and how strongly bleaching happens. Even the same coral species can show different bleaching thresholds in different regions, since long-term exposure to different environments can shape their ability to handle heat. 4 The resilience Mechanism of Corals 4.1 Physiological recovery pathways The restoration of coral functions and symbiotic relationships requires a series of physiological regulations. First, heat shock proteins (HSPs) are expressed, which help fold damage proteins and buffer heat stress damage. Secondly, corals may reduce energy consumption and accelerate recovery by regulating their metabolic rate. Long-term studies (Kaneohe Bay, Hawaii) have shown that some corals significantly improve their heat tolerance through "acclimatization" after heatwaves (Brown et al., 2023). 4.2 Ecological restoration mechanism In addition to individual physiological recovery, ecological restoration is also of vital importance. This includes larval settlement, community structure reconstruction, etc. Young corals (larvae) have unique adaptive strategies to heat stress: at high temperatures, they reduce basal metabolism and increase nitrogen absorption to maintain a stable relationship with symbiotic algae, thereby avoiding bleaching (Huffmyer et al., 2024). In addition, supplementary populations can be enhanced through ecological engineering-based methods (such as designing basement structures that are more conducive to the settlement of young corals). 4.3 Mechanism of failed recovery Recovery failure often occurs under conditions where the frequency of heat waves intensifies and the recovery time is insufficient. Long-term monitoring shows that although some coral species survive after heatwaves, their
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