Composition, sources, and bioavailability of nitrogen in a longitudinal gradient from freshwater to estuarine waters

Jani, Jariani and Toor, Gurpal S. (2018) Composition, sources, and bioavailability of nitrogen in a longitudinal gradient from freshwater to estuarine waters. Water Research, 137. pp. 344-354. ISSN 0043-1354

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Official URL: https://doi.org/10.1016/j.watres.2018.02.042

Abstract

Nitrogen (N) transport from land to water is a dominant contributor of N in estuarine waters leading to eutrophication, harmful algal blooms, and hypoxia. Our objectives were to (1) investigate the composition of inorganic and organic N forms, (2) distinguish the sources and biogeochemical mechanisms of nitrate–N (NO3–N) transport using stable isotopes of NO3 − and Bayesian mixing model, and (3) determine the dissolved organic N (DON) bioavailability using bioassays in a longitudinal gradient from freshwater to estuarine ecosystem located in the Tampa Bay, Florida, United States. We found that DON was the most dominant N form (mean: 64%, range: 46–83%) followed by particulate organic N (PON, mean: 22%, range: 14–37%), whereas inorganic N forms (NOx–N: 7%, NH4–N: 7%) were 14% of total N in freshwater and estuarine waters. Stable isotope data of NO3 − revealed that nitrification was the main contributor (36.4%), followed by soil and organic N sources (25.5%), NO3 − fertilizers (22.4%), and NH4 + fertilizers (15.7%). Bioassays showed that 14 to 65% of DON concentrations decreased after 5-days of incubation indicating utilization of DON by microbes in freshwater and estuarine waters. These results suggest that despite low proportion of inorganic N forms, the higher concentrations and bioavailability of DON can be a potential source of N for algae and bacteria leading to water quality degradation in the estuarine waters.

Item Type: Article
Uncontrolled Keywords: Nitrogen; Stable isotopes; Dissolved organic nitrogen; Bioavailability; Freshwater; Estuarine; Tampa bay estuary
Subjects: Q Science > Q Science (General)
Q Science > QD Chemistry
Divisions: Faculty of Science > Dept of Chemistry
Depositing User: Ms. Juhaida Abd Rahim
Date Deposited: 02 Aug 2019 03:37
Last Modified: 02 Aug 2019 03:37
URI: http://eprints.um.edu.my/id/eprint/21754

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