International Journal of Marine Science, 2025, Vol.15, No.1, 15-27 http://www.aquapublisher.com/index.php/ijms 25 The effects of heat stress on oysters are more intuitive and can lead to large-scale thermal death and reproduction failure of shellfish. In recent years, unprecedented ocean heat waves have occurred on the northwest coast of North America, causing high mortality rates of local farming and wild oysters, which has attracted attention. In addition to the immediate blow to population size, such events also have potential genetic effects. Extreme high temperatures may quickly eliminate families with poor heat tolerance, and surviving individuals tend to carry specific heat-tolerant alleles or phenotypes (Zhao et al., 2024). The study found that after experiencing a heat wave, the frequency of specific alleles of certain heat shock protein genes in the wild Pacific oyster population in Canada's BC province has increased significantly, suggesting a strong choice. Ocean acidification and heating also have a composite effect. On the one hand, heating can aggravate the adverse effects of acidification on juveniles, because juvenile metabolism accelerates at high temperatures and requires more stable calcification. On the other hand, it is interesting that certain studies have shown that cross-generational exposure may induce partial relief: allowing parental oysters to live under acidified conditions, and their offspring exhibit higher survival rates in acidified water than controls. This means that there are mechanisms of epigenetic adaptation or phenotypic plasticity that can offset the problem of insufficient genetic diversity to some extent. However, this plasticity is not infinite and needs to be supported by genetic mutation in more severe situations. 7.3 Research on genetic improvement and adaptive evolution in coping with environmental stress Faced with multiple pressures such as climate change and environmental pollution, research and application of genetic means to improve the adaptability of oyster populations has become an important direction. Choosing breeding is one of the most realistic and feasible ways at present. By breeding oysters in controlled environments for generations, people can target favorable variants, thereby cultivating more high temperature, acid or disease-resistant strains. Advances in genomics and molecular breeding technology provide new tools for accelerating genetic improvement. Genome-wide selection can predict its adult resistant phenotype by marking at the juvenile shellfish stage, thereby screening the best seedlings and greatly shortening the breeding cycle. Gene editing techniques (such as CRISPR/Cas9) have the potential to target the modification of known antiresistance-related genes in the oyster genome (Guo et al., 2018). In addition to artificial improvement, promoting natural adaptive evolution is also one of the strategies to enhance population stress resistance. The so-called "adaptive evolution" refers to the process of accumulation of favorable genes in wild populations under natural selection. To this end, we need to create conditions to allow as many different genetic types as possible to participate in reproduction and guide the selection of directions through environmental management. Acknowledgments The authors gratefully acknowledge the support provided by Chen J.J. and thank the two peer reviewers for their suggestions. Conflict of Interest Disclosure The authors confirm that the study was conducted without any commercial or financial relationships and could be interpreted as a potential conflict of interest. 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