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Fluctuations of nitrogen isotope ratio of gobiid fish (Isaza) specimens and sediments in Lake Biwa, Japan, during the 20th century
Author(s) -
Ogawa Nanako O.,
Koitabashi Tadatoshi,
Oda Hirotaka,
Nakamura Toshio,
Ohkouchi Naohiko,
Wada Eitaro
Publication year - 2001
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2001.46.5.1228
Subject(s) - eutrophication , sediment , fish <actinopterygii> , denitrification , nitrogen , environmental science , nitrate , watershed , δ15n , oceanography , structural basin , sedimentary rock , isotopes of nitrogen , geology , stable isotope ratio , hydrology (agriculture) , fishery , δ13c , ecology , geochemistry , nutrient , biology , chemistry , geomorphology , physics , geotechnical engineering , organic chemistry , quantum mechanics , machine learning , computer science
Nitrogen isotope ratios (Δ 15 N) of sediment and formalinߚfixed fish specimens (Isaza fish, Chaenogobius isaza, Tanaka), which had been collected and preserved over 40 yr, were used to provide a new methodology to reconstruct recent eutrophication and historical changes in the nitrogen cycle in Lake Biwa. Δ 15 N records of Isaza fish collected in the north basin of Lake Biwa, a lake that had been rapidly eutrophicated in the last several decades, showed a rapid increase from the early 1960s to 1980s with an overall amplitude of >3‰. The same trend was simultaneously observed from that of sedimentary nitrogen. We evaluated several factors controlling Δ 15 N of Isaza fish and sediments during the 20th century and concluded that an increase of Δ 15 N was either associated with an increase in loading nitrate with high Δ 15 N values from the watershed or enhanced denitrification in the lake.