Title of Research: 23-5-06
Ecotoxicological risk assessment of microplastics -as a model case of Osaka BayPrincipal Investigator:
Yoshifumi Horie, PhD (Associate Professor, Kobe University, Research Center for Inland Seas
5-1-1 Fukaeminami-machi, Higashinada-ku, Kobe 658-0022, JAPANCollaborators:
Hideo Okamura (Professor), Research Center for Inland Seas, Kobe University
Gomez Christopher (Professor), Graduate School of Maritime Sciences, Kobe University
Akira Ijiri (Associate Professor), Graduate School of Maritime Sciences, Kobe University
Kazuyo Yamaji (Associate Professor), Graduate School of Maritime Sciences, Kobe University
5-1-1 Fukaeminami-machi, Higashinada-ku, Kobe 658-0022, JAPANSummary of Research:
We investigated microplastic residues in the sea surface water of Osaka Bay area, in order to set
the microplastic exposure conditions. As a results, plastic particles accounted for only 22.4% ofparticles. Microplastic pollution values in the Osaka Bay (range abundance of 7.6 ot 61.4 particles/L)
is consistent with previous reports in other semi-enclosed bays. Fragments appeared in the size
less than 100 μm, fibers had much smaller sizes in the range 10–30 μm, films appeared in the size
range 34–409 μm, and beads appeared in the size around 30 μm. Atmospheric transport plays acritical role in the deposition and accumulation of microplastics in marine environments. Therefore,
we aimed to investigate the abundance of microplastics in rainwater outfalls from five prefectures(Hokkaido, Akita, Fukuoka, Hiroshima, and Hyogo) across Japan The overall microplastics
concentrations ranged from 379 to 1,790 particles/L.
Fish are thought to employ color vision to detect microplastics, prompting ourinvestigation into microplastic ingestion patterns in three marine fish species, Chrysiptera cyanea,
Hypoatherina tsurugae, and Plotosus japonicus, and three freshwater fish species, Rhodeus
ocellatus, Pseudorasbora parva, and Misgurnus anguillicaudatus. Notably, C. cyanea, P. japonicus,and R. ocellatus exhibited color preferences in microplastic ingestion, with C. cyanea favoring red,
P. japonicus preferring blue and gray, and R. ocellatus favoring red and yellow.
Finally, using D. magna (crustacean) and zebrafish (fish), we investigated whether thetime required to expel microplastics varies when ingestion occurs through a food-chain. As aresults, we found that microplastics excretion occurs within 48 h and 24 h for direct ingestion andingestion through food chain (via D. magna), respectively.
Timeline:
March 1, 2023
Topics:2023 年度 日化協 LRI 研究報告会にて発表「閉鎖性海域 大阪湾をモデルケースにした MP の生態リスク評価」
セタックジャパン ミニシンポジウムにて発表「Abundance of microplastics in a semi-enclosed
Osaka Bay area -Ecotoxicological risk assessment of microplastics-」
Publications:
第 26 回日本水環境学会シンポジウムにて発表「閉鎖性海域 大阪湾をモデルケースにした MP の生態リスク評価」
令和 5 年度 海洋プラスチックごみ学術シンポジウムにて発表「「食う−食われる」過程を介した マ
イクロプラスチックの排出時間の変化」
Horie Y, Mitsunaga K, Yamaji K, Hirokawa S, Uaciquete D, Ríos JM, Yap CK, Okamura
H. Variability in microplastic color preference and intake among selected marine and freshwater
fish and crustaceans,Discover Ocean, 1(5), 2024.
Horie Y, Uaciquete D, Mitsunaga K, Akkajit P, Ríos JM, Naija A. Food chain-mediated variation inexcretion times of microplastics: Unraveling the interactions with plasticizers. Regional Studies inMarine Science. 69, 103343, 2024.