Massive Nitrogen Loss Over the Western Indian Continental Shelf During Seasonal Anoxia: Evidence From Isotope Pairing Technique
| Autor: | Syed Wajih Ahmad Naqvi, Gayatri Shirodkar, Marcel M. M. Kuypers, Hema Naik, Amit Sarkar, Anil Pratihary, Gaute Lavik |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
0106 biological sciences
Denitrification 010504 meteorology & atmospheric sciences lcsh:QH1-199.5 seasonal hypoxia/anoxia chemistry.chemical_element Ocean Engineering lcsh:General. Including nature conservation geographical distribution Aquatic Science Oxygen minimum zone Oceanography 01 natural sciences chemistry.chemical_compound Nitrate Ammonium lcsh:Science 0105 earth and related environmental sciences Water Science and Technology geography Global and Planetary Change geography.geographical_feature_category denitrification nitrogen loss Continental shelf 010604 marine biology & hydrobiology Nitrogen Anoxic waters DNRA chemistry Anammox Environmental chemistry anammox lcsh:Q |
| Zdroj: | Frontiers in Marine Science Frontiers in Marine Science, Vol 7 (2020) |
| ISSN: | 2008-2010 |
| Popis: | The western Indian continental shelf houses the world's largest naturally formed coastal low-oxygen zone that develops seasonally during the summer monsoon. We investigated multiple reductive nitrogen transformation pathways and quantified their rates in this system through anaerobic incubations with additions of N-15-labeled substrates during the anoxic period for three consecutive years (2008-2010). Addition of N-15 labeled ammonium ((NH4+)-N-15) resulted in low to moderate anaerobic ammonia oxidation (Anammox) rates in about half of our incubations from the oxygen depleted waters. In contrast, incubations with labeled nitrite ((NO2-)-N-15) led to large production of N-30(2) over N-29(2) in all incubation experiments, indicating denitrification to be the dominant N-loss pathway. Rates of dissimilatory nitrate/nitrite reduction to ammonium (DNRA) were found to be highly variable and were lower by an order of magnitude than the denitrification rates. Extrapolation of average rates over the sampling periods and volume of anoxic waters showed large nitrogen removal (3.70-11.1 Tg year(-1)) which is about three times as high as the previously reported estimate (1.3-3.8 Tg year(-1)). Despite the small area it occupies, this shallow seasonal anoxic zone may account for as much as 20-60% the of the total annual fixed nitrogen loss in the perennial oxygen minimum zone of the Arabian Sea. |
| Databáze: | OpenAIRE |
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