Sediment samples from the East China and Yellow seas collected adjacent to continental China were found to have lower δ15N values (expressed as δ15N = [15N:14Nsample/15N:14Nair - 1] × 1000‰ the sediment 15N:14N ratio relative to the air nitrogen 15N:14N ratio). In contrast, the Arctic sediments from the Chukchi Sea, the sampling region furthest from China, showed higher δ15N values (2-3‰ higher than those representing the East China and the Yellow sea sediments). Across the sites sampled, the levels of sediment δ15N increased with increasing distance from China, which is broadly consistent with the decreasing influence of anthropogenic nitrogen (NANTH) resulting from fossil fuel combustion and fertilizer use. We concluded that, of several processes, the input of NANTH appears to be emerging as a new driver of change in the sediment δ15N value in marginal seas adjacent to China. The present results indicate that the effect of NANTH has extended beyond the ocean water column into the deep sedimentary environment, presumably via biological assimilation of NANTH followed by deposition. Further, the findings indicate that NANTH is taking over from the conventional paradigm of nitrate flux from nitrate-rich deep water as the primary driver of biological export production in this region of the Pacific Ocean.
Bibliographical noteFunding Information:
The authors sincerely thank the scientists who contributed to the Nitrogen Cycle in the Ocean, Past and Present database (see Table S1; http://www.ncdc.noaa.gov/paleo/pubs/nicopp/ nicopp.html),20 atmospheric nitrogen deposition data (Oak Ridge National Laboratory Distributed Active Archive Center; https://daac.ornl.gov/),16 and the surface ocean nitrate concentration data (the World Ocean Atlas 2013; http:// www.nodc.noaa.gov/OC5/woa13/woa13data.html).24 Sediment samples from the East China and Yellow seas were obtained from the Library of Marine Samples of South Sea Research Institute, Korea Institute of Ocean Science and Technology. This research was supported by Global Research Project (2013K1A1A2A02078278) and Midcareer Researcher Program (2015R1A2A1A05001847) funded by the NRF of Ministry of Science, ICT and Future Planning. Partial support was provided by "Management of Marine Organisms causing Ecological Disturbance and Harmful Effects" funded by the Ministry of Oceans and Fisheries. Seung-Il Nam was supported by the NRF of Ministry of Science, ICT, and Future Planning (2015M1A5A1037243).
© 2017 American Chemical Society.
ASJC Scopus subject areas
- General Chemistry
- Environmental Chemistry