Variation of environmental DNA in sediment at different temporal scales in nearshore area of Tokyo Bay.
Environmental DNA (eDNA) is a non-invasive and less labor-intensive tool for biological survey. The advantages enable more frequent sampling work, but there is a lack of fundamental field data on the variation of eDNA in sediment in different timescales. We conducted a yearlong sampling at two marine parks of Tokyo Bay (Odaiba Marine Park and Kasai Marine Park) to investigate the temporal variation of sediment eDNA at scales of one year, one month and one tidal period. Grandidierella japonica, an indicator benthic species of water quality in Japan and also an invasive species in other countries, was chosen as target species. In yearlong scales, the total eDNA content and the copy number of the amphipod eDNA in both parks showed a seasonal variation pattern as low in cold season (89 ± 14 ng DNA/g sediment, 583 ± 64 copies/g sediment) and high in warm season (884 ± 97 ng DNA/g sediment, 9,501 ± 3,553 copies/g sediment). In scales shorter than one month, eDNA kept stable and did not show clear variation. The results indicated that eDNA in sediment is useful for biological survey by reflecting the well-averaged state of the species abundance in the environment and not showing the erroneous sudden variation in a short timescale.