Isotopic evidence for preferential transport of fertilizer nitrogen into the northern Gulf of Mexico during high water discharge
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1.
Boston College
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2.
National Sun Yat-sen University
- 3. Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, Taiwan
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4.
University of California, Santa Barbara
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5.
California Institute of Technology
Abstract
Anthropogenic nitrogen inputs from the Mississippi-Atchafalaya River Basin have caused substantial environmental challenges in the northern Gulf of Mexico, such as coastal eutrophication, harmful algal blooms, and seasonal hypoxia. Addressing these issues requires a better understanding of the complex sources of nitrogen, which include fertilizers, groundwater, manure, and sewage. In this study, we analyzed the nitrogen isotopic composition of dissolved nitrate and particulate nitrogen from the Wax Lake Delta, a major distributary of the Mississippi-Atchafalaya River Basin that flows into the Gulf of Mexico. Our findings revealed that during the wet season, δ15N values of both nitrate and particulate nitrogen were consistently 2-3‰ lower compared to the dry season. This suggests that fertilizer-derived nitrogen, which has lower δ15N, is predominantly exported to the Gulf of Mexico during periods of high water discharge. These findings imply that adjusting fertilizer application timing could help reduce nitrogen loading and mitigate its environmental impact on the Gulf of Mexico.
Copyright and License
© The Author(s) 2024.
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Acknowledgement
This work was funded by the Engineer Research and Development Center of US Army Corps of Engineers. Sample splits were kindly provided by the NASA Delta-X project.
Contributions
X.T.W. and G.K.L designed the study. G.K.L, J.A.N. and M.P.L. collected the samples used in the study. J.J.C., M.L., T.K. and H.D. analyzed the nitrate isotopes in the Stable Isotope Biogeochemistry Lab at Boston College. G.K.L. and Z.Y. analyzed the particulate nitrogen content isotopes at University of California, Santa Barbara. J.J.C. and X.T.W. wrote the manuscript. All authors contributed to the interpretation of the data and provided input to the manuscript.
Data Availability
The data sets are available within the Supplementary Data and https://daac.ornl.gov/cgi-bin/dataset_lister.pl?p=41.
Supplemental Material
Transparent Peer Review file (PDF)
Supplementary Information (PDF)
Description of Additional Supplementary Files (PDF)
Supplemental data (XLSX)
Reporting Summary (PDF)
Files
Additional details
- United States Army Corps of Engineers
- Engineer Research and Development Center
- Accepted
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2024-11-04Accepted
- Caltech groups
- Division of Geological and Planetary Sciences
- Publication Status
- Published