Eutrophication of mountain lakes in Japan due to increasing deposition of anthropogenically produced dust
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O R I GI N A L A R T IC L E
Narumi K. Tsugeki • Tetsuro Agusa • Shingo Ueda Michinobu Kuwae • Hirotaka Oda • Shinsuke Tanabe Yukinori Tani • Kazuhiro Toyoda • Wan-lin Wang Jotaro Urabe
Eutrophication of mountain lakes in Japan due to increasing deposition of anthropogenically produced dust Received: 7 April 2012 / Accepted: 13 August 2012 / Published online: 28 September 2012 The Ecological Society of Japan 2012
Abstract Atmospheric dust has wide-reaching effects, not only influencing climate conditions, but also ecosystems. The eastern region of the Asian continent is one of the largest emitters of dust in the world, and recent economic growth in the region has been accompanied by an increase in anthropogenic emissions. However, the effects of increased Asian dusts on aquatic ecosystems are not well understood. We examined fossil pigments and zooplankton remains from 210Pb-dated sediments taken from high mountain lakes of Hourai-Numa and Hachiman-Numa, located in the Towada-Hachimantai National Park of Japan Islands, to uncover historical changes in the phyto- and zooplankton community over the past 100 years. Simultaneously, we measured the geochemical variables of TOC, TN, TP, d13C, d15N, and lead isotopes (207Pb/206Pb, 208 Pb/206Pb) in the sediments to identify environmental factors causing such changes. As a result, despite few anthropogenic activities in the watersheds, alpine lakes in Japan had increased algal and herbivore plankton
biomasses by 3–6 fold for recent years depending on the surrounding terrestrial vegetation and landscape conditions. Biological and biogeochemical proxies recorded from the lake sediments showed that this eutrophication occurred after the 1990s when P deposition increased as a result of atmospheric loading of dust transported from the Asian continent. The continued increase of anthropogenically produced dust may therefore impart damaging impacts on mountain ecosystems even if they are protected from direct anthropogenic disturbances. Keywords Asian dust Æ Anthropogenic deposition Æ Eutrophication Æ Mountain lakes Æ Phosphorus
Introduction A wide range of natural sources, including wind-eroded soils, contributes to the atmospheric deposition of
N. K. Tsugeki Æ W. Wang Æ J. Urabe Graduate School of Life Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
M. Kuwae Senior Research Fellow Center, Ehime University, Matsuyama 790-8577, Japan
Present address: N. K. Tsugeki (&) Senior Research Fellow Center, Ehime University, Matsuyama 790-8577, Japan E-mail: [email protected] Tel.: +81-89-927-8179 Fax: +81-89-927-9846
H. Oda Chronological Research, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
T. Agusa Department of Legal Medicine, Shimane University, Izumo 693-8501, Japan
Y. Tani Institute for Environmental Sciences, University of Shizuoka, Shizuoka 422-8526, Japan
Present address: T. Agusa Center for Marine Environmental Studies, Ehime University, Matsuyama 790-8577, Japan
K. Toyoda Graduate School of Environmental Science, Hokkaido University, K
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