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Effect of dissolved organic carbon quality on microbial decomposition and nitrification rates in stream sediments

Freshwater Biology

By:
and
DOI: 10.1046/j.1365-2427.2002.00776.x

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Abstract

1. Microbial decomposition of dissolved organic carbon (DOC) contributes to overall stream metabolism and can influence many processes in the nitrogen cycle, including nitrification. Little is known, however, about the relative decomposition rates of different DOC sources and their subsequent effect on nitrification. 2. In this study, labile fraction and overall microbial decomposition of DOC were measured for leaf leachates from 18 temperate forest tree species. Between 61 and 82% (mean, 75%) of the DOC was metabolized in 24 days. Significant differences among leachates were found for labile fraction rates (P < 0.0001) but not for overall rates (P = 0.088). 3. Nitrification rates in stream sediments were determined after addition of 10 mg C L-1 of each leachate. Nitrification rates ranged from below detection to 0.49 ??g N mL sediment-1 day-1 and were significantly correlated with two independent measures of leachate DOC quality, overall microbial decomposition rate (r = -0.594, P = 0.0093) and specific ultraviolet absorbance (r = 0.469, P = 0.0497). Both correlations suggest that nitrification rates were lower in the presence of higher quality carbon. 4. Nitrification rates in sediments also were measured after additions of four leachates and glucose at three carbon concentrations (10, 30, and 50 mg C L-1). For all carbon sources, nitrification rates decreased as carbon concentration increased. Glucose and white pine leachate most strongly depressed nitrification. Glucose likely increased the metabolism of heterotrophic bacteria, which then out-competed nitrifying bacteria for NH4+. White pine leachate probably increased heterotrophic metabolism and directly inhibited nitrification by allelopathy.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Effect of dissolved organic carbon quality on microbial decomposition and nitrification rates in stream sediments
Series title:
Freshwater Biology
DOI:
10.1046/j.1365-2427.2002.00776.x
Volume
47
Issue:
1
Year Published:
2002
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Freshwater Biology
First page:
65
Last page:
74
Number of Pages:
10