Response of bay ostracod assemblages to Late Holocene sea-level, centennial-scale climate, and human-induced factors in northeast Beppu Bay, Japan
Response of bay ostracod assemblages to Late Holocene sea-level, centennial-scale climate, and human-induced factors in northeast Beppu Bay, Japan
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DOI：
10.1016/j.marmicro.2021.102002
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发表时间：
2022-06-06
影响因子：
1.9
通讯作者：
Kawano, Shigenori
中科院分区：
文献类型：
--
作者：
Irizuki, Toshiaki;Takahashi, Jun;Kawano, Shigenori
本研究阐明了在过去约3000年中，在日本的小型底栖海湾介形虫组合的百年尺度的变化与各种人为和自然环境因素。这些因素推断通过综合多代理方法的高分辨率地质分析的核心沉积物从一个浅海湾沿海平原，沿着与考古和历史记录的文献调查。根据介形虫组合的多元分析，定义了五个区间。介形类组合在世纪以前是稳定的，这是由于与海平面逐渐上升有关的加积沉积作用。此后，研究地点附近的一个桑迪的发展，稳定的海平面，区域构造，区域百年尺度的气候变化可能与厄尔尼诺类似的南方涛动（ENSO），以及洪水缓解人类定居在沿海平原的综合因素，触发了潮滩和潮下带的桑迪与海草床的形成。自世纪以来，这对近海海湾介形类组合产生了显著影响。人类活动的影响，如自世纪后期以来的填海和各种人工建设，导致海草床的消失，粗沉积物输入近海海湾，并增加营养负荷。因此介形虫的组合发生了巨大的变化。陆地与海洋边界附近的介形虫组合受到多种复杂因素的影响，例如全新世晚期的区域气候以及沉积和人类活动过程。
This study clarified the centennial-scale changes in meiobenthic bay ostracod assemblages in Japan over the past approximately 3000 years with relation to various human-induced and natural environmental factors. These factors were inferred via integrated multiproxy methods of high-resolution geological analyses of core sediments obtained from a shallow bay off a coastal plain, along with literature surveys of archeological and historical records. Five intervals were defined based on multivariate analyses of ostracod assemblages. The ostracod assemblage was stable before around the 6th century because of aggradational sedimentation related to gradual increases in sea level. Since then, the composite factors such as the development of a sandy spit near the study site, stable sea level, regional tectonics, regional centennial-scale climatic change possibly related to El Nin similar to o Southern Oscillation (ENSO), and flood mitigation by human settlement in the coastal plains triggered the formation of tidal flats and subtidal sandy areas with seagrass beds. This has markedly influenced offshore bay ostracod assemblages since around the 12th century. Anthropogenic impacts, such as reclamation and various artificial constructions since the late 20th century caused the disappearance of seagrass beds, input of coarser sediment into offshore bays, and increased nutrient loads. Therefore, ostracod assemblages have changed drastically. Ostracod assemblages near the boundary between land and sea have been affected by multiple complex factors, such as regional climate and depositional and human-induced processes during the Late Holocene.