2:45 PM - 3:00 PM
[U10-05] DNA metabarcoding on the sediment core and seasonal monitoring of modern plankton community with a view to improve the paleoenvironmental reconstruction
Keywords:sedaDNA, protist, Anthropocene, Holocene, taphonomy
The plankton community is an excellent environmental indicator because of their high biomass, low trophic level and sensitive response to environmental changes. In addition, DNA metabarcoding, a technique which can comprehensively detect the biological components, has been actively used in recent years mainly in the field of biology (especially in field ecology). Although DNA metabarcoding has begun to be used in the field of geosciences, it is difficult to presume the structure of past ecosystems only by such analysis, since sediment cores contain the DNA of only a small part of the various aquatic organisms that lived at that time. Given this situation, we tried to solve this problem from a cross-disciplinary perspective between current biology and geoscience.
A seasonal monitoring of modern plankton community was conducted from May 2020 to March 2021 in Lake Shinji and Nakaumi Lagoon, Japan. In each survey, water and surface sediment samples were taken at six stations. A sediment core of ca. 4 m was also sampled from the floor of Lake Shinji. DNA metabarcoding focusing on plankton was performed for the water and sediment samples, and the taxonomic composition and its seasonal changes were clarified.
As a result of the seasonal monitoring, the species composition of the plankton community in Lake Shinji and the Nakaumi Lagoon changed significantly after October-November. The taxonomic composition of plankton in the water largely differed from that in the surface sediments. It was suggested that some taxa, such as copepods and ciliates, were quickly decomposed immediately after their death and settlement, resulting in a relatively small proportion of the remains being preserved in the sediment, and therefore, their species diversity and abundance is possibly underestimated in the sediment analysis. The data obtained in this study will help to clarify the "preservation pattern of each species in sediments" (i.e., how much and what kind of organisms are preserved in sediments). Using these data, the results of the sediment core analysis could be corrected, and the paleo-environment and paleo-ecosystem would be reconstructed with higher precision than ever before.
A seasonal monitoring of modern plankton community was conducted from May 2020 to March 2021 in Lake Shinji and Nakaumi Lagoon, Japan. In each survey, water and surface sediment samples were taken at six stations. A sediment core of ca. 4 m was also sampled from the floor of Lake Shinji. DNA metabarcoding focusing on plankton was performed for the water and sediment samples, and the taxonomic composition and its seasonal changes were clarified.
As a result of the seasonal monitoring, the species composition of the plankton community in Lake Shinji and the Nakaumi Lagoon changed significantly after October-November. The taxonomic composition of plankton in the water largely differed from that in the surface sediments. It was suggested that some taxa, such as copepods and ciliates, were quickly decomposed immediately after their death and settlement, resulting in a relatively small proportion of the remains being preserved in the sediment, and therefore, their species diversity and abundance is possibly underestimated in the sediment analysis. The data obtained in this study will help to clarify the "preservation pattern of each species in sediments" (i.e., how much and what kind of organisms are preserved in sediments). Using these data, the results of the sediment core analysis could be corrected, and the paleo-environment and paleo-ecosystem would be reconstructed with higher precision than ever before.