Foraminiferal responses to flood events, human activities and sea-level changes in brackish Lake Jinzai, Shimane Prefecture, southwest Japan, in the last 60 years

DOI Web Site 80 References
  • Nomura Ritsuo
    Foraminiferal Laboratory, Faculty of Education and Research Center for Coastal Lagoon Environments, Shimane University
  • Roser Barry P.
    Interdisciplinary Faculty of Science and Engineering, Shimane University

Bibliographic Information

Other Title
  • 島根県神西湖（汽水湖）における過去60年間の洪水，人間活動および海面水位変動に対する有孔虫の応答

Search this article

Abstract

We examined the impacts of both sea-level changes and flood events on the foraminiferal assemblages in brackish Lake Jinzai, northeast Shimane Prefecture, southwest Honshu, Japan, over the last 60 years. Sea-level rises that occurred around the coast of Japan in the 1950s and mid-1970s are recognized by increases in the number of foraminiferal individuals per gram of sediment, as represented by the brackish species Ammonia “beccarii” and the coastal species Elphidium excavatum. Sea-level rise after the 1990s was not accompanied by an increase in the number of foraminiferal individuals, indicating that the foraminiferal abundance is not primarily controlled by sea-level changes, but rather by some other factors. Long-term information of annual COD (Chemical Oxygen Demand) changes in brackish water from the 1980s indicates that organic contents are a major factor controlling the foraminiferal abundances. We confirmed that the sea-level rise from the late 1980-90s to the present did not contribute to the foraminiferal abundances, as did those of the 1950 and 1970s.<BR>These foraminiferal species also have responded to flood events in three different ways : (1) A. “beccarii” developed first, and E. excavatum occurred later ; (2) only A. “beccarii” occurred ; and (3) both species developed together. The foraminifera responded to the short-term events by increase of individual numbers, suggesting enhanced productivity. Accordingly, flood events contribute an increased supply of food resources for foraminifera, as provided by higher organic contents or nutrients.

Journal

References(80)*help

See more

Keywords

Details 詳細情報について

Report a problem

Back to top