期刊
LIMNOLOGY AND OCEANOGRAPHY
卷 66, 期 3, 页码 652-666出版社
WILEY
DOI: 10.1002/lno.11630
关键词
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资金
- National Science Foundation of China [NSFC: 41606093, U1806211, 42076035]
- Youth Talent Support Program of the Laboratory for Marine Ecology and Environmental Science, Pilot National Laboratory for Marine Science and Technology (Qingdao) [LMEES-YTSP-2018-02-04]
- National Research and Development program of China [2016YFA0600902, 2016YFA0601302]
- Ministry of Science & Technology of P. R. China [2011CB409802]
- Aoshan Talents Program
- Qingdao National Laboratory for Marine Science and Technology [2015ASTP-OS08]
- Taishan Scholars Programme of Shandong Province
Decreases in bottom water oxygen concentration lead to reductions in sediment oxygen uptake and penetration depth, while denitrification rates increase. Nitrate and ammonium fluxes show complex behavior under hypoxic conditions. Changes in benthic nutrient cycling under hypoxia enhance the retention of nitrogen, exacerbating oxygen deficiency.
The effects of bottom water oxygen concentration on sediment oxygen uptake, oxygen penetration depth, nitrate and ammonium fluxes, anammox, denitrification, dissimilatory nitrate reduction to ammonium, nitrification, and mineralization were investigated off the Changjiang estuary and its adjacent East China Sea, by combining a seasonal comparison with three artificially induced bottom water oxygen conditions (oxic, ambient, and severe hypoxia). A 50% decrease in in-situ bottom water oxygen concentrations between May and August, led to decreases in the average sediment oxygen uptake and oxygen penetration depth by 23% and 29%, respectively. Anammox rates decreased by a factor of 2.5, and the relative contribution of anammox to the total benthic N-loss decreased from 20% to 7.4%. However, denitrification rates increased, leading to an overall benthic N-loss rate of 0.85 mmol N m(-2)d(-1). At the same time, an increasing contribution of dissimilatory nitrate reduction to ammonium to total nitrate reduction led to higher recycling of inorganic nitrogen during hypoxia in August. Under artificially induced conditions of severe hypoxia, there was a sharp decrease in both sediment oxygen uptake and benthic N-loss rates by 88% and 38%, respectively. Nitrate and ammonium fluxes showed complex behavior at different sites which could be related to the repression of sedimentary nitrification below a bottom water oxygen threshold of 9.7 mu M and increasing dissimilatory nitrate reduction to ammonium. Taken together, our results indicate that changes in benthic nutrient cycling under seasonal hypoxia enhance the retention of both organic and inorganic nitrogen, thereby exacerbating oxygen deficiency.
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