International Journal of Marine Science, 2025, Vol.15, No.1, 15-27 http://www.aquapublisher.com/index.php/ijms 24 of farmed oysters to deviate from the wild population. If the two reproductive and mating occurs, it will change the genetic frequency of the wild population; second, farmed oysters introduced by foreign strains or species will escape and compete with local oysters or hybridize, causing gene invasion or germplasm to become mixed. In response to wild-cultural genetic interference, various measures can be taken to alleviate it. The first is to use sterile or semi-sterile breeding strains, such as breeding triploid oysters, which are widely used to prevent summer reproduction and improve meat quality. Due to their extremely low fertility, these triploids significantly reduce the possibility of hybridization with wild oysters and fundamentally reduce the risk of infiltration. Secondly, optimizing the breeding layout and avoiding the establishment of large-scale farms near important wild oyster beds is also a way to reduce interference. Third, it is very necessary to establish a genetic monitoring plan. Regular sampling and analysis of wild populations in the breeding area and surrounding areas. If the genetic diversity or endemic allelic frequency of wild populations is found to be significantly reduced, the breeding management strategy needs to be adjusted. In addition, for the problem of the spread of imported alien oyster species (such as Pacific oysters in Europe) in the wild, management is usually based on prevention and control, and it is necessary to limit its competition for local oysters and habitat occupation as much as possible. If the alien species cannot be eradicated, it should be monitored for signs of hybridization with the local species. 7 Future Threats and Response: Genetic Response in Environmental Change 7.1 Prediction of the impact of climate change on distribution range and gene flow Global climate change is changing the marine environment at an unprecedented rate, which will profoundly affect the distribution pattern and genetic connectivity of oysters. Sea water heating is one of the most direct influencing factors. As the average temperature rises, suitable habitats for many oyster species will experience geographical displacement, which is expected to move towards higher latitudes overall. The model predicts that by the mid-21st century, the distribution of temperate oysters (such as European flat oysters and eastern oysters) may expand by hundreds of kilometers, while habitats on the southern edge may shrink due to excessive water temperature and frequent hypoxia events. This means that genetic exchanges between currently distant populations may be possible in the future through new mediated habitats (Abe, 2021). Changes in the current pattern are also an important aspect of climate change affecting gene flow. Global warming may cause weakening of ocean circulation or offsetting paths. For example, if the Kuroshio pathway moves northward or changes in intensity, the northwestern Pacific Pacific oyster juvenile transport chain may be disturbed, thereby changing the gene exchange rate between the Chinese-Japanese populations (Scanes et al., 2021). Sea level rise will flood new lowlands, creating new coastal lagoons and mangrove habitats, which may play a role in increasing oyster habitat continuity and promoting genetic connectivity in certain areas. But on the other hand, too fast sea level rise may exceed the rate of upward growth of oyster reefs, causing the reef to be submerged and killed, causing the original continuous distribution to break, and close attention is needed. The increasing frequency of extreme weather events is also part of climate change. Hurricanes, warm winters, ocean heat waves, etc. will cause great ups and downs in the oyster population. Frequent large-scale deaths will significantly reduce the effective size of the population, aggravating genetic drift and loss of diversity. 7.2 The perturbation mechanism of marine acidification and heat stress on genetic structure In addition to temperature changes, ocean acidification and heat stress are another set of environmental stresses brought about by climate change, which may have hidden and long-term effects on the genetic structure of oysters. Marine acidification directly affects the calcification and survival of oyster juveniles. A large number of experimental studies and a series of meta-analysis have confirmed that elevated water pCO_2 will reduce the growth rate of oyster juveniles and increase early mortality. Long-term observations of the Sydney Rock oysters in Australia show that the average shell length of the offspring of oysters propagated under high CO_2 conditions significantly reduces the average shell length and the survival rate is reduced. This selective pressure means that specific genotypes that can survive an acidification environment will increase in the proportion of the next generation, thereby changing the allelic frequency of the population.
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