Microbial incorporation of nitrogen in stream detritus

We adapted the chloroform fumigation method to determine microbial nitrogen (N) and microbial incorporation of ^sup 15^N on three common substrates [leaves, wood and fine benthic organic matter (FBOM)] in three forest streams. We compared microbial N and ^sup 15^N content of samples collected during...

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Bibliographic Details
Published in:Hydrobiologia 2001-11, Vol.464 (1-3), p.27-35
Main Authors: SANZONE, Diane M, TANK, Jennifer L, MEYER, Judy L, MULHOLLAND, Patrick J, FINDLAY, Stuart E. G
Format: Article
Language:English
Subjects:
Animal and plant ecology
Animal, plant and microbial ecology
Biological and medical sciences
Creeks & streams
Fresh water ecosystems
Fundamental and applied biological sciences. Psychology
Fungi
General aspects. Techniques
Methods and techniques (sampling, tagging, trapping, modelling...)
Microbial ecology
Microbiology
Research parks
Synecology
USA, New Hampshire, Bear Brook
USA, North Carolina, Upper Ball Creek
USA, Tennessee, Walker Branch
Various environments (extraatmospheric space, air, water)
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Summary:We adapted the chloroform fumigation method to determine microbial nitrogen (N) and microbial incorporation of ^sup 15^N on three common substrates [leaves, wood and fine benthic organic matter (FBOM)] in three forest streams. We compared microbial N and ^sup 15^N content of samples collected during a 6-week ^sup 15^N-NH^sub 4^ tracer addition in each stream. The ^sup 15^N was added during late autumn to Upper Ball Creek, a second-order stream at the Coweeta Hydrologic Lab, North Carolina, U.S.A.; during spring to Walker Branch, a first-order stream on DOE's Oak Ridge National Environmental Research Park, Tennessee; and during summer to Bear Brook, a first-order stream in the Hubbard Brook Experimental Forest, New Hampshire. FBOM was the largest component of organic matter and N standing stock in all streams. Microbial N represented the highest proportion of total N in leaves and least in FBOM in Walker Branch and Bear Brook. In Upper Ball Creek, the proportion of microbial N was higher in FBOM than in used biofilm or on leaves. Standing stock of microbial N on leaves and in FBOM ranged from 37 mg N m^sup -2^ in Bear Brook to 301 mg N m^sup -2^ in Walker Branch. Percent of detrital N in living microbial cells was directly related to total microbial biomass (fungal and bacterial biomass) determined from microscopic counts. [partial differential]^sup 15^N values for microbes were generally higher than for bulk detritus, which would result in higher [partial differential]^sup 15^N values for animals preferentially consuming or assimilating microbial cells. The proportion of ^sup 15^N taken up by detritus during the ^sup 15^N experiments that remained in microbial cells by the end of the experiments was highest for wood biofilm in Upper Ball Creek (69%), leaves in Walker Branch (65%) and FBOM in Upper Ball Creek (31%). Lower retention proportions (
ISSN:0018-8158
1573-5117
DOI:10.1023/A:1013930102876