Japan Geoscience Union Meeting 2023

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[E] Oral

B (Biogeosciences ) » B-PT Paleontology

[B-PT03] Biomineralization and Geochemistry of Proxies

Fri. May 26, 2023 3:30 PM - 4:45 PM Exhibition Hall Special Setting (3) (Exhibition Hall 8, Makuhari Messe)

convener:Takashi Toyofuku(Japan Agency for Marine-Earth Science and Technology (JAMSTEC)), Hiroshi Kitazato(Tokyo University of Marine Science and Technology (TUMSAT)), Jelle Bijma(Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung), Kotaro Hirose(Institute of Natural and Environmental Sciences, University of Hyogo), Chairperson:Takashi Toyofuku(Japan Agency for Marine-Earth Science and Technology (JAMSTEC)), Kotaro Hirose(Institute of Natural and Environmental Sciences, University of Hyogo), Jelle Bijma(Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung), Hiroshi Kitazato(Tokyo University of Marine Science and Technology (TUMSAT))


3:45 PM - 4:00 PM

[BPT03-07] Temporal variation of diatom assemblages under the influence of anthropogenic pollution in the estuarine lake Nakaumi, southwest Japan

*Kotaro Hirose1, Akira Tsujimoto2, Koji Seto3, Toshiaki Irizuki4 (1.Institute of Natural and Environmental Sciences, University of Hyogo, 2.Faculty of Education, Shimane University, 3.Estuary Research Center, Shimane University, 4.Department of Geoscience, Shimane University)

Keywords:estuarine lake, bottom sediment, anthropogenic change, diatom assemblage, aquatic ecosystem, Lake Nakaumi

We investigated the temporal variations of diatom assemblages for 600 years in the sediment from Lake Nakaumi, an estuarine lake in Japan, to place the consequences of human induced pollutions on coastal primary producers.
In the early 20th century, CNS and many kinds of heavy metals show a rapid increase, eutrophic species of diatoms such as small Thalassiosira species increased, and then Neodelphineis pelagica increaced. This rapid change indicates that the drastic shift in the aquatic environment was caused by loads of industrial and domestic wastes and the intense stagnation due to the construction of the port area. Multiproxy records which revert to the past value in the 1960s suggest the environmental recovery in Nakaumi. This reverting trend occurred much earlier than that of the metropolitan bay area such as Tokyo Bay and Osaka Bay in which the environmental degradation progressed more after the 1960s. This change would be a significant case study for predicting environmental changes in urban coasts in response to the mitigation of pollution.