著者

Kyoshiro Hiki Fumiyuki Nakajima

出版者

Japan Society on Water Environment

雑誌

Journal of Water and Environment Technology (ISSN:13482165)

巻号頁・発行日

vol.20, no.5, pp.137-144, 2022 (Released:2022-10-10)

参考文献数

32

被引用文献数

1

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Microplastics adversely affect organisms through physical damage, inhibition of food assimilation, and/or toxicity of chemical leachates. We investigated the influence of feeding mode on microplastic ingestion by using polystyrene microbeads (diameter: 4.1 and 20.6 μm) and the estuarine benthic amphipod Grandidierella japonica, which can switch between filter-feeding and deposit-feeding modes. When provided with sediment, amphipods burrowed and were in the filter-feeding mode; they ingested 4.1 and 20.6 μm beads in the ratio at which the two sizes were suspended in the water. Without sediment, however, the amphipods were mainly in the deposit-feeding mode and ingested more 20.6 μm beads, which tended to be deposited on the bottom, compared with 4.1 μm beads. In addition, the number of microbeads ingested by the amphipods in sediment increased as the amount of food provided (i.e., fish food TetraMin) increased, whereas no such increase was observed for the amphipods without sediment. These results indicate that the microbead ingestion was dependent on feeding mode (i.e., presence/absence of sediment), amount of food, and distribution of microbeads (i.e., sizes of microbeads). To better understand the ingestion, accumulation, and toxicity of microplastics in aquatic environments, we recommend that more attention be paid to behavioral changes in benthic organisms.

著者

Nan Wei Fumiyuki Nakajima Tomohiro Tobino

出版者

Japan Society on Water Environment

雑誌

Journal of Water and Environment Technology (ISSN:13482165)

巻号頁・発行日

vol.17, no.3, pp.153-162, 2019 (Released:2019-06-10)

参考文献数

37

被引用文献数

6

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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.