International Journal of Marine Science, 2025, Vol.15, No.3, 118-129 http://www.aquapublisher.com/index.php/ijms 126 sequences should be supplemented every year, and taxonomic changes in the database should be calibrated in a timely manner. Management departments can also participate in the formulation of relevant standards to include eDNA monitoring as part of the official monitoring specifications (Thomsen et al., 2024). With the interaction between scientific research and application, continuously improving the process to make it easier and more cost-controllable, which is also the key to improving promotion. At present, each water sample costs about a few hundred yuan from collection to analysis. If the cost can be reduced through local reagents or combined sampling, it will be conducive to large-scale application. Figure 2 eDNA detection operation experiment (Adapted from Douglas et al., 2020) 7 The Application Value of eDNA in Hainan's Marine Ecological Protection and Management 7.1 Assisted biological monitoring of marine protected areas There are many marine reserves and coral reef nature reserves around Hainan Island, such as Hainan Coral Reef National Nature Reserve (West Island-Dianjiezhou Area). Effective protected area management relies on dynamic monitoring of biological resources within the area. Traditional protected areas monitoring often focuses on indicators such as coral coverage, economic fish resources, and lacks timely grasp of overall biodiversity. Applying eDNA technology to protected area monitoring can achieve broad-spectrum biological monitoring: a water sample can detect the existence of microfishes to large migratory fishes in one water sample, thereby comprehensively assessing the ecological health status of protected area. eDNA can also assist in monitoring and protecting effectiveness. Gold et al. (2021) found that eDNA can sensitively reflect the differences in fish schools inside and outside California reserves, proving that the establishment of reserves does maintain a high species richness. In Hainan, the eDNA results in waters adjacent to protected areas and non-protected areas can also be compared to evaluate the spillover effects and effectiveness of protected areas. If the species diversity and rare species frequency in the protected area is significantly higher than that outside, it means that the conservation measures are effective. On the contrary, if there is no obvious difference, the protection strength or scope needs to be reviewed. Because the eDNA method is fast and non-invasive, monitoring frequency can be higher, and the acquired time series data can help capture seasonal migration or abnormal events (such as fish school changes after coral bleaching). For groups that are difficult to evaluate in traditional methods (such as nocturnal fish and juvenile fish), eDNA also provides an observation window, making the reserve manager more clear. In the future, eDNA monitoring may be one of the standard projects for routine monitoring of Hainan Marine Protection Areas, providing a scientific basis for assessment and adjustment of protection effects.
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