Development of modern benthic ecosystems in eutrophic coastal oceans: The foraminiferal record over the last 200 years,Osaka Bay,Japan |
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Authors: | Akira Tsujimoto Moriaki Yasuhara Ritsuo Nomura Hideo Yamazaki Yoshikazu Sampei Kotaro Hirose Shusaku Yoshikawa |
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Affiliation: | 1. Division of Biology and Geosciences, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan;2. Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013-7012, USA;3. Foraminiferal Laboratory, Faculty of Education, Shimane University, Matsue, Shimane 690-8504, Japan;4. Department of Life Science, School of Science and Engineering, Kinki University, Higashiosaka, Osaka 577-8502, Japan;5. Department of Geoscience, Faculty of Science and Engineering, Shimane University, Matsue, Shimane 690-8504, Japan |
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Abstract: | The ecosystem dynamics of a modern benthic community in Osaka Bay was studied by analyzing sediment cores and fossil foraminifera deposited during the past 200 years. The results suggest that the high-density/low-diversity assemblage has appeared in the early 1900s, coinciding with the eutrophication of the bay resulting from the Japanese industrial revolution. This assemblage proliferated during the period 1960 to 1970 when the eutrophication and bottom-water hypoxia were most pronounced. The development of the assemblage has been characterized by an increase in the relative and absolute abundance of eutrophication-tolerant species (Ammonia beccarii, Eggerella advena, and Trochammina hadai) and a decrease in many other foraminiferal species, such as Ammonia tepida, Elphidium, Miliolinella subrotunda, and Valvulineria hamanakoensis, that are unable to tolerate low-oxygen conditions. Approximately thirty years after the imposition of discharge restrictions in the 1970s, this assemblage continues to predominate in the inner part of the bay, and E. advena is currently found across the entire bay. These records make a significant contribution to understanding the long-term relationship between anthropogenic impact and ecosystem change. |
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Keywords: | Benthic foraminifera Ecosystem Eutrophication Hypoxia Osaka Bay Species diversity |
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