Comparison of different sampling methods in the analysis of cryptofaunal community characteristics in coral reefs

Firstly, significant differences (p< 0.05) were observed among the three methods in representing the species diversity of cryptofauna at Lingyang Reef. The ARMS method detected an average of 298.68 species, followed by the SeDNA method with 286.00 species, while the RU method yielded the lowest count of 124.33 species, with considerable variability among samples. Secondly, although all three methods confirm that the cryptofauna of Lingyang Reef include major phyla such as Arthropoda, Mollusca, and Porifera, biases in the representation of community composition are evident across the sampling approaches.

The SeDNA method primarily captures sediment-dwelling groups, including Annelida (e.g., Spionida), Nematoda, and mobile Mollusca, and mobile mollusks; the RU method mainly captures predatory crabs and Amphilepidida inhabiting complex crevices; while the ARMS method, in addition to the taxa detected by the other methods, also provides information on sessile taxa such as Porifera, Bryozoa, and certain unidentified Mollusca.

In summary, the ARMS method demonstrates advantages in capturing cryptofaunal diversity and community composition characteristics, facilitating standardized data comparisons. However, it may overlook organisms inhabiting coral rubbles and sediments. Enhancing the structural diversity of ARMS and supplementing it with SeDNA sampling can provide a more comprehensive reflection of cryptofaunal community characteristics.

With advancements in sequencing technology and the expansion of cryptofaunal databases, future efforts should establish a ‘layered, multi-method integrated’ monitoring system centered on standardized observation devices, supported by in situ sampling for immediate verification, and supplemented by environmental DNA for ecological completeness. This approach will offer a scientifically reliable technical solution for the long-term, efficient, and precise assessment of coral reef biodiversity.