11:00 〜 11:15
[HQR04-07] Environmental DNA analyses focusing on the plankton community and aquatic plants to reconstruct the paleo-environment
★Invited Papers
キーワード：DNAメタバーコーディング、堆積物古代DNA、原生生物、堆積物コア、人新世
The DNA metabarcoding (DNA-MB) and quantitative PCR are promising methods to elucidate the composition and DNA quantity of organisms contained in environmental samples. In the brackish waters, plankton community and aquatic plants are suitable research target to clarify the paleo-environment because these organisms contain the primary producers. Moreover, they possess large biomass and respond sensitively to environmental changes. We conducted a sedimentary study targeted on plankton community and aquatic plants in Lake Shinji, Japan. The salinity of the lake is relatively low (the PSU is ca. 1–5), but it was a semi-closed bay filled with sea water before 2000 years ago. Previous studies reported that the concentration of sulfur, which indicates the inflow of sea water, decreased in a certain period during the past 2000 years, and therefore, it is hypothesized that in this period, the semi-closed bay became an almost freshwater lake. This hypothesis was, however, not supposed by enough biological evidences.
Given this situation, some sediment cores of 1-4 m were sampled in 2020-2022 from the lake. Quantitative PCRs targeted on two aquatic plants (Potamogeton panormitanus and Stuckenia pectinata) were conducted for the sediment samples in order to clarify the fluctuation of DNA quantity of these species. The DNA-MB focused on plankton was also performed for the same samples.
The quantitative PCRs on two aquatic plants showed a clear tendency that the two species were detected chiefly in the samples lower than ca. 2.5 m in the core depth. By the DNA-MB, marine plankton were mainly detected in the same samples, and the plankton composition was largely different among the samples upper and lower than ca. 2.5 m. This core depth corresponded to the timing of the sulfur decrease, and the age was estimated at 1200–1290 CE. These results suggest that the desalinization of the lake and the drastic change of ecosystem started around 1200–1290 CE. This study shows that environmental DNA analyses of plankton community and aquatic plants are effective in reconstructing paleo-environments.
Given this situation, some sediment cores of 1-4 m were sampled in 2020-2022 from the lake. Quantitative PCRs targeted on two aquatic plants (Potamogeton panormitanus and Stuckenia pectinata) were conducted for the sediment samples in order to clarify the fluctuation of DNA quantity of these species. The DNA-MB focused on plankton was also performed for the same samples.
The quantitative PCRs on two aquatic plants showed a clear tendency that the two species were detected chiefly in the samples lower than ca. 2.5 m in the core depth. By the DNA-MB, marine plankton were mainly detected in the same samples, and the plankton composition was largely different among the samples upper and lower than ca. 2.5 m. This core depth corresponded to the timing of the sulfur decrease, and the age was estimated at 1200–1290 CE. These results suggest that the desalinization of the lake and the drastic change of ecosystem started around 1200–1290 CE. This study shows that environmental DNA analyses of plankton community and aquatic plants are effective in reconstructing paleo-environments.