Seasonal isotopic and isotopomeric signatures of nitrous oxide produced microbially in a eutrophic estuary.

Mar Pollut Bull

School of Marine Sciences, Sun Yat-Sen University, Zhuhai, China; Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Zhuhai, China. Electronic address:

Published: July 2024

Anthropogenic input of excess nutrients stimulates massive nitrous oxide (NO) production in estuaries with distinct seasonal variations. Here, nitrogen isotopic and isotopomeric signatures were utilized to investigate the seasonal dynamics of NO production and nitrification at the middle reach of the eutrophic Pearl River Estuary in the south of China. Elevated NO production primarily via ammonia oxidation (> 1 nM-N d) occurred from April to November, along with increased temperature and decreased dissolved oxygen concentration. This consistently oxygenated water column showed active denitrification, contributing 20-40 % to NO production. The water column microbial NO production generally constituted a minor fraction (10-15 %) of the estuarine water-air interface efflux, suggesting that upstream transport and tidal dilution regulated the dissolved NO inventory in the middle reach of the estuary. Nitrification (up to 3000 nM-N d) played a critical role in bioavailable nitrogen conversion and NO production, albeit with NO yields below 0.05 %.

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http://dx.doi.org/10.1016/j.marpolbul.2024.116528DOI Listing

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