Premium
Spatial and Seasonal Variations of Stable Isotope Ratios of Particulate Organic Carbon and Nitrogen in the Surface Water of the Kuroshio
Author(s) -
Kodama Taketoshi,
Nishimoto Atsushi,
Horii Sachiko,
Ito Daiki,
Yamaguchi Tamaha,
Hidaka Kiyotaka,
Setou Takashi,
Ono Tsuneo
Publication year - 2021
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1029/2021jc017175
Subject(s) - seasonality , submarine pipeline , environmental science , photic zone , particulates , nitrate , oceanography , isotopes of nitrogen , total organic carbon , nitrogen , environmental chemistry , geology , nutrient , phytoplankton , chemistry , ecology , organic chemistry , biology
Seasonal stable isotope ratios of carbon and nitrogen (δ 13 C and δ 15 N) in the particulate organic matter (POM) of the euphotic layer were investigated around the Kuroshio from 2008 to 2019 ( n = 474). Significant seasonality in POM δ 13 C and δ 15 N were observed in the coastal and offshore areas divided by the northern edge of the Kuroshio. Seasonal mean δ 13 C was highest during the summer (−23.2 ± 1.1‰ and −23.7 ± 1.1‰ in coastal and offshore areas, respectively) and lowest during the winter (−24.6 ± 0.8‰ and −25.0 ± 0.9‰ in coastal and offshore areas, respectively) in both areas. Seasonal mean δ 15 N exhibited different spatial variations. The mean δ 15 N value in the coastal area was the lowest during the winter (1.0 ± 1.9‰) and increased to a similar level (∼3‰) during the other three seasons. In contrast, δ 15 N in the offshore area near the surface decreased from the spring (2.5 ± 1.5‰) to the summer (1.2 ± 1.7‰). These spatial and seasonal differences in δ 15 N are significant in generalized linear models and the generalized additive models, and suggest that the nitrogen sources used in biological production differ between coastal and offshore areas and between seasons. Nitrate originating in deeper water and rivers is the main sources used for new production throughout the year in the coastal area. Contributions from atmospheric deposition and nitrogen fixation are significant in the offshore area during the summer, while nitrate originating in deeper water is main during winter, spring, and fall in the offshore area.