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Environmental changes recorded in coastal lagoon sediments-the local effects and the global phenomena-

沿海泻湖沉积物记录的环境变化-局部影响和全球现象-

基本信息

批准号：
07309009
负责人：
TAKAYASU Katsumi
金额：
$ 9.66万
依托单位：
Shimane University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07309009/
关键词：
Coastal lagoon Brackish-water zone Lake deposit Bottom topography Environmental change Sea-level change Human effect in environments High resolution stratigraphy 高精度古環境分析浜名湖サロマ湖網走湖

项目摘要

The purpose of this research project is to make clear the environmental characteristics and the forming processes of the representative coastal lagoons by extracting the local effects and the global phenomena, and to present the fundamental data for discussing on the influences of the sea level raising and the predicting artificial change of environment. For this purpose, we carried out the collaborative works in such coastal lagoons as Saroma-ko, Abashiri-ko, Hanama-ko, Nakaumi, Shinji-ko, etc.In Lagoon Saroma-ko facing the Sea of Okhotsk, the change in water quality caused by the artificial cutting of sand bar is clearly indicated by the change in diatom assemblages, which affected the organic matter content of the bottom sediment as well as the assemblages of benthic fauna. Dredging the bottom of River Abashiri for expanding the port area accelerated the upstreaming of high saline waters to Lake Abashiri-ko. Consequently it raised the level of halocline and expanded anoxic environment in bottom waters.In Lagoon Hamana-ko, the opening of Imagireguchi strait, which is believed to be caused by a big earthquake in 1498, is recorded by the change of diatom assemblages in the core samples. The abnormal bottom topography in the northern area of this Lake found by echo sounding is probably related to that event. These phenomena suggest that the lagoons facing the Pacific Ocean are strongly effected by the tectonic movements as well as the eustatic sea level change.In case of the lagoons facing the Sea of Japan, such as Lake Shinji-ko, Lake Nakaumi, etc., the change in water quality and sedimentary facies are totally controlled by the meteorological effects of heavy rains, drastic change of atmospheric pressure, and seasonal strong wind. The detection and differentiation of these effects in core samples are important subject in the discussion on the global climatic change in the past to the future.

本研究的目的是通过提取局部效应和全球现象，弄清具有代表性的滨海泻湖的环境特征和形成过程，为讨论海平面上升的影响和预测环境的人为变化提供基础数据。为此，我们在Saroma-ko、Abashiri-ko、Hanama-ko、Nakaumi、Shinci-Ko等沿海泻湖开展了合作工作。在面对鄂霍次克海的Saroma-Ko泻湖，人工切割沙洲引起的水质变化明显体现在硅藻组合的变化上，这影响了底层沉积物的有机质含量和底栖动物的组合。疏浚阿巴希里河河底以扩大港口面积，加速了高盐度水向阿巴希里科湖的逆流。在Hamana-Ko泻湖，通过岩心样品中硅藻组合的变化记录了Imagireguchi海峡的开放，据信是由1498年的一次大地震引起的。回波测深在该湖北部地区发现的异常海底地貌可能与该事件有关。这些现象表明，面对太平洋的泻湖受到构造运动和海平面变化的强烈影响，而面对日本海的泻湖，如新济湖、中泉湖等，水质和沉积相的变化完全受暴雨、大气压力剧烈变化和季节性大风的气象效应的控制。在岩心样品中检测和区分这些效应是过去和未来全球气候变化讨论的重要课题。