Conclusions
Targeting various fragment sizes of mitochondrial and nuclear genes of Japanese jack mackerels, we showed that the addition of BAC suppressed eDNA degradation and increased its initial concentration. In addition, BAC enabled to maintain the number of marine fish species detected by eDNA metabarcoding in seawater samples. Our study suggests the use of BAC for the preservation of various types of eDNA from water samples under various environmental conditions regardless of eDNA detection strategies (i.e., species-specific or metabarcoding assay); accordingly, we could increase the yield of target eDNA and the number of detected species, which may prevent the underestimation of species abundance and richness via eDNA analysis.
Some issues remain to be addressed in the future. First, all eDNA studies using BAC have targeted fish and amphibians, and it is unknown whether BAC effectively preserves eDNA released from other vertebrates and invertebrates. Different production sources of eDNA among taxa might lead to different performances of BAC in preserving aqueous eDNA. In addition, understanding the interactions between BAC and environmental factors is necessary. Takahara et al. (2020) reported a statistically marginal interaction between BAC treatment and storage temperature on eDNA yields. Further studies are required to determine the effects of water chemistry and environmental conditions on the eDNA preservation performance of BAC. Information on the performance of BAC, including that revealed in this study, would simplify the application of eDNA analysis in natural environments and enable the effective and precise monitoring of biodiversity conservation and resource management.