Records of environmental and ecological changes related to excavation in varve sediment from Lake Hiruga in central Japan
Records of environmental and ecological changes related to excavation in varve sediment from Lake Hiruga in central Japan
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日本中部昼贺湖泥沙挖掘相关的环境和生态变化记录
DOI：
10.1007/s10933-022-00251-y
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
K
中科院分区：
文献类型：
--
作者：
Seto;K.;Katsuki;K.;Tsujimoto;A.;Kitagawa;J.;Yamada;K
在位于日本中部日本海沿着的半封闭泻湖--Hiruga湖，重建了自世纪中期以来的次年度尺度的环境和生态系统变化。Hiruga湖是三田五湖之一，通过人工隧道佐贺隧道与水月湖相连。硅质浮游植物（硅藻，silicoflagellates，和金藻孢囊）和元素组成（碳，氮，硫）的层状沉积物进行分析，以确定不规则的危害和人为隧道建设对泻湖生态系统的影响。在这个泻湖中，沉积物纹层沉积后，第一次佐贺隧道重新挖掘于1844-1848年，和浮游植物的优势类群已经改变了每次重新挖掘。隧道开挖和水闸建设对水蛭湖水体中总氮、总有机碳、淡水硅藻和金藻孢囊的行为产生了强烈的影响。除了人为影响外，沉积物还显示出对水蛭湖生态系统的极端危害影响。水蛭湖硅藻、硅鞭藻丰度和硫含量的峰值与当地地震事件有密切关系。1928-1930年日本海沿岸局部沉降引起的相对高的海平面导致了与Hiruga湖的活跃海水交换。此外，淡水硅藻类群和金藻孢囊的峰值显示了该湖泊由局部极端事件引起的淡水化事件，例如公元1900年前后的持续洪水。
Sub-annual-scale environmental and ecosystem changes since the mid-18th century were reconstructed in a semi-closed lagoon, Lake Hiruga, located along the Sea of Japan in central Japan. Lake Hiruga is one of the Mikata Five Lakes and is connected to Lake Suigetsu through an artificial tunnel, the Saga Tunnel. Analyses of siliceous phytoplankton (diatoms, silicoflagellates, and chrysophyte cysts) and elemental composition (carbon, nitrogen, sulfur) of laminated sediments were conducted to determine the impacts of irregular hazards and anthropogenic tunnel construction on the lagoon ecosystem. In this lagoon, sediment laminae were deposited after the first Saga Tunnel re-excavation in 1844–1848, and the dominant phytoplankton taxa have changed with each re-excavation. The behaviors of total nitrogen, total organic carbon, freshwater diatom taxa, and chrysophyte cysts in Lake Hiruga are strongly affected by tunnel excavation and water gate construction. In addition to anthropogenic effects, the deposits show extreme hazard impacts of the Lake Hiruga ecosystem. The peaks of marine diatom taxa, silicoflagellate abundance, and sulfur content of Lake Hiruga showed close relationships with the local earthquake event. A relatively high sea level in the coast of Sea of Japan by local subsidence induced active seawater exchange with Lake Hiruga around AD 1928–1930. Furthermore, the peaks of freshwater diatom taxa and chrysophyte cyst showed a freshening event of this lake caused by local extreme events, such as continuous flooding around AD 1900.