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| Titel |
Nitrification and inorganic nitrogen distribution in a large perturbed river/estuarine system: the Pearl River Estuary, China |
| VerfasserIn |
M. Dai, L. Wang, X. Guo, W. Zhai, Q. Li, B. He, S.-J. Kao |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 5, no. 5 ; Nr. 5, no. 5 (2008-09-03), S.1227-1244 |
| Datensatznummer |
250002822
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| Publikation (Nr.) |
 copernicus.org/bg-5-1227-2008.pdf |
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| Zusammenfassung |
| We investigated the spatial distribution and seasonal variation of dissolved
inorganic nitrogen in a large perturbed estuary, the Pearl River Estuary,
based on three cruises conducted in winter (January 2005), summer (August 2005)
and spring (March 2006). On-site incubation was also carried out for
determining ammonium and nitrite oxidation rates (nitrification rates). We
observed a year-round pattern of dramatic decrease in NH4+,
increase in NO3−, but insignificant change in NO2− in
the upper estuary at salinity ~0–5. However, species and
concentrations of inorganic nitrogen at upper estuary significantly changed with
season. In winter, with low runoff, the most upper reach of the Pearl River
Estuary showed relatively low rates of ammonia oxidation (0–5.4 μmol
N L−1 d−1) and nitrite oxidation (0–5.2 μmol N L−1 d−1),
accompanied by extremely high concentrations of ammonia (up to
>800 μmol L−1) and nitrate (up to >300 μmol L−1). In
summer, the upper estuary showed higher nitrification rates (ammonia
oxidation rate ~1.5–33.1 μmol N L−1 d−1, nitrite
oxidation rate ~0.6–32.0 μmol N L−1 d−1) with lower
concentrations of ammonia (<350 μmol L−1) and nitrate (<120 μmol L−1).
The Most Probable Number test showed relatively lower
nitrifier abundance in summer at most sampling stations, indicating a
greater specific nitrification rate per cell in the warm season. Temperature
appeared to control nitrification rates to a large degree in different
seasons. Spatial variability of nitrification rates appeared to be
controlled by a combination of many other factors such as nutrient
concentrations, nitrifier abundance and dissolved oxygen (DO)
concentrations. In addition to aerobic respiration, nitrification
contributed significantly to the consumption of DO and production of
free CO2 at upper estuary. Nitrification-induced consumption accounted for up to
approximately one third of the total water column community DO consumption
in the upper estuary during the surveyed periods, boosting environmental
stress on this large estuarine ecosystem. |
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