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Nitrogen Fixation in the Intertidal Sediments of the Yangtze Estuary: Occurrence and Environmental Implications
Author(s) -
Hou Lijun,
Wang Rong,
Yin Guoyu,
Liu Min,
Zheng Yanling
Publication year - 2018
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2018jg004418
Subject(s) - nitrogen fixation , benthic zone , reactive nitrogen , estuary , nitrogen cycle , nitrogen , environmental chemistry , nutrient pollution , environmental science , ecosystem , denitrification , ecology , chemistry , biology , pollution , organic chemistry
Nitrogen fixation is a microbial‐mediated process converting atmospheric dinitrogen gas to biologically available ammonia or other molecules, and it plays an important role in regulating nitrogen budgets in coastal marine ecosystems. In this study, nitrogen fixation in the intertidal sediments of the Yangtze Estuary was investigated using nitrogen isotope tracing technique. The abundance of nitrogen fixation functional gene ( nifH ) was also quantified. The measured rates of sediment nitrogen fixation ranged from 0.37 to 7.91 nmol N g −1 hr −1 , while the abundance of nifH gene varied from 2.28 × 10 6 to 1.28 × 10 8 copies g −1 in the study area. The benthic nitrogen fixation was correlated closely to the abundance of nifH gene and was affected significantly by salinity, pH, and availability of sediment organic carbon and ammonium. It is estimated that sediment nitrogen fixation contributed approximately 9.3% of the total terrigenous inorganic nitrogen transported annually into the Yangtze estuarine and coastal environment. This result implies that the occurrence of benthic nitrogen fixation acts as an important internal source of reactive nitrogen and to some extent exacerbates nitrogen pollution in this aquatic ecosystem.