Carbon and nitrogen dynamics in the coastal Sea of Japan inferred from 15 years of measurements of stable isotope ratios of Calanus sinicus
Carbon and nitrogen dynamics in the coastal Sea of Japan inferred from 15 years of measurements of stable isotope ratios of Calanus sinicus
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DOI：
10.5194/os-18-295-2022
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发表时间：
2022-03
期刊：
影响因子：
3.2
通讯作者：
Ken-ichi Nakamura;Atsushi Nishimoto;S. Yasui-Tamura;Y. Kogure;Misato Nakae;N. Iguchi;H. Morimoto;T. Kodama
中科院分区：
文献类型：
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作者：
Ken-ichi Nakamura;Atsushi Nishimoto;S. Yasui-Tamura;Y. Kogure;Misato Nakae;N. Iguchi;H. Morimoto;T. Kodama
摘要。日本海的氮和碳动态均已发生变化。我们假设哲水蚤（Calanus sinicus）的碳和氮稳定同位素比值（δ13C和δ15N）能够记录日本海沿岸环境的变化。因此，在2006年至2020年的春季，对四个站点的这些同位素比值进行了监测，以确定碳和氮动态的变化。δ13C值介于 -24.7‰到 -15.0‰之间，从春季水华期（2月 - 3月）到水华后期（6月 - 7月）呈下降趋势。这些变化归因于中华哲水蚤的生理变化以及浮游植物的δ13C含量变化。δ15N值介于2.8‰到8.8‰之间，表明中华哲水蚤是次级生产者；从水华期到水华后期δ15N值上升的趋势归因于浮游植物的δ15N增加。广义线性模型（GLM）方法表明，超过70%的δ13C变化可由海表温度（SST）、海表叶绿素a浓度（SSC）、中华哲水蚤的碳氮比（C/N比）以及地理差异来解释。GLM中δ13C的残差逐年下降（ - 0.035‰ yr⁻¹）。中华哲水蚤的δ15N的GLM表明，除了SST、SSC、C/N比和地理差异外，δ15N还随发育阶段或性别而变化。雌性中华哲水蚤和第五期桡足幼体的δ15N值分别最低和最高。GLM中δ15N的残差没有呈现出显著的年际趋势。这些结果表明，在过去15年中，日本海沿岸的次级生产者的碳同位素比值呈线性变化。此外，该地区碳动态的变化已被记录并观察到对海洋生态系统产生影响，然而尽管该海域含氮营养物质输入增加，但氮动态却未被记录。
Abstract. Both nitrogen and carbon dynamics have changed in the Sea of Japan. We hypothesized that the carbon and nitrogen stable isotope ratios (δ13C and δ15N) of the copepod Calanus sinicus could record changes in the coastal environment of the Sea of Japan. Consequently, these isotope ratios were monitored during the spring at four stations from 2006 to 2020 to identify the changes in carbon and nitrogen dynamics. The δ13C values ranged from −24.7 ‰ to −15.0 ‰ and decreased from the spring bloom (February–March) to the post-bloom (June–July) seasons. These variations were attributed to changes in the physiology of both C. sinicus and phytoplankton δ13C contents. The δ15N values range from 2.8 ‰ to 8.8 ‰, indicating that C. sinicus is a secondary producer; the tendency of the δ15N values to increase from the bloom to the post-bloom seasons was attributable to an increase in the δ15N of phytoplankton. A generalized linear model (GLM) approach indicated that >70 % of the variations in δ13C can be explained by sea surface temperature (SST), sea surface chlorophyll a concentration (SSC), carbon:nitrogen ratio of C. sinicus (C/N ratio), and geographic differences. The residuals of δ13C in the GLM decreased yearly (−0.035 ‰ yr−1). The GLM for δ15N of C. sinicus indicated that δ15N varies with the stage or sex in addition to SST, SSC, C/N ratio, and geographic differences. The δ15N values of female C. sinicus and stage V copepodites were the lowest and highest, respectively. The residuals of δ15N in the GLM did not exhibit a significant interannual trend. These results suggest that the carbon isotope ratio in the secondary producer has linearly changed in the coastal Sea of Japan over the past 15 years. Moreover, the changes in carbon dynamics of this area have been recorded and observed to impact the marine ecosystem, while the nitrogen dynamics have not been recorded despite the increasing nitrogenous nutrient inputs in this sea.