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A 7‐year increasing trend of 15 N in sinking particles at the mouth of the Tokyo Bay
Author(s) -
Sukigara Chiho,
Saino Toshiro
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2006gl025982
Subject(s) - bay , estuary , environmental science , oceanography , sediment , atmospheric sciences , geology , geomorphology
A sediment trap experiment was conducted for 7 years with sampling at 7 days interval at the Tokyo Bay mouth. The δ 15 N of the trapped particles showed an increasing trend (0.17 ‰ y −1 ) from 1995 to 2001. The trend is larger in summer than in winter particles. During summer, the δ 15 N shows large variation where maxima increase while the minima stay nearly constant. The summertime elevation in δ 15 N is due to increased contribution of freshly derived 15 N rich particles produced in the inner‐bay surface water. The high δ 15 N in trapped particles lagged one or two weeks behind the >50 mm d −1 rainfall events. Freshwater supplied by heavy rainfall appears to accelerate estuarine circulation and results in increased contribution of inner‐bay surface water particles. The increased frequency of the short‐term heavy rainfall events in metropolis Tokyo during our observation could be a cause for the 7 year increasing trend of δ 15 N in the sinking particles.