Sedimentary eDNA provides different information on timescale and fish species composition compared with aqueous eDNA

Aqueous environmental DNA (eDNA) analysis has been applied to the monitoring of various ecosystems and taxa, and the characteristics of aqueous eDNA have been previously studied. In contrast, although sedimentary eDNA has been used to restore past information, the characteristics of sedimentary eDNA are not well understood. In this study, we compared the properties of sedimentary and aqueous eDNA of macro‐organisms. First, to clarify the preservation ability of sediments, we compared the difference in decay rates between aqueous and sedimentary eDNA using samples collected from a biotope (an artificial pond prepared with concrete). Next, to clarify the biological information retained in sedimentary eDNA both qualitatively and quantitatively, we compared eDNA concentrations between sediment and water samples collected simultaneously from a lake, and the fish species detected by eDNA metabarcoding were also compared. The results demonstrated the following: (a) the decay rate (decreased eDNA copy number divided by the initial eDNA copy number per unit time) of sedimentary eDNA (0.00033 ± 0.000049 [mean ± SE]/hr) was lower than that of aqueous eDNA (0.01863 ± 0.0011/hr); (b) sedimentary eDNA concentration of the mitochondrial marker of three fish species was higher than aqueous eDNA concentration for the same sample weight (12.5–1,456.9 times); and (c) the species composition obtained by metabarcoding was not significantly different between sediment and water; however, considering the lower decay rate of sedimentary eDNA, using both sample types may provide more comprehensive information of species distribution. Thus, sedimentary eDNA analysis will expand future biomonitoring and ecological studies by providing a difference in timescale.