The influence of the balance of inorganic and organic nitrogen on the trophic dynamics of microbial food webs.

Davidson, Keith, Gilpin, Linda, Hart, Mark C, Fouilland, Eric, Mitchell, Elaine, Calleja, Ignacio Alvarez, Laurent, Celine, Miller, Axel E J and Leakey, Raymond J G (2007) The influence of the balance of inorganic and organic nitrogen on the trophic dynamics of microbial food webs. Limnology & Oceanography, 52 (5). pp. 2147-2163. ISSN 0024-3590

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A nutrient-manipulation mesocosm study was conducted in Norwegian coastal waters to determine the effect
on a nitrogen-limited microbial food web of changes in the relative concentrations of dissolved organic and
inorganic nitrogen (N). Four replicated treatments were studied: no N addition, inorganic N, organic N, or
a 50 : 50 mix of inorganic and organic N. Comprehensive abundance, biomass, and rate measurements were made
over the 20-d experiment. The form of N available influenced species composition, succession, and the efficiency
of carbon (C) incorporation. Inorganic N generated a bloom of the diatom Leptocylindrus danicus, even though
silicon concentrations were below 1 mmol L21. The c-proteobacteria initially competed effectively with diatoms
for inorganic N, exhibiting high productivity and escaping grazing control. Organic N, when available alone, was
utilized more slowly by the microbial community, with diatom growth, fueled by regenerated N, achieving a lower
peak abundance. A more diverse diatom species assemblage was also evident. The c-proteobacteria were less
prevalent and net bacterial productivity was initially lower when the N source was organic and, in contrast to the
response following inorganic N addition, the bacterial community was initially grazer controlled. A rapid
succession of heterotrophic grazers occurred but with differences in species and their contribution to biomass
between treatments. The efficiency of C-biomass production was lower when the N source was purely organic.
However, when both inorganic and organic N were available, biomass yield was greater than the mean of the two single N source treatments

Item Type: Article
Print ISSN: 0024-3590
Uncontrolled Keywords: nutrient-manipulation mesocosm; nitrogen-limited microbial food web; C-biomass;
University Divisions/Research Centres: Faculty of Health, Life & Social Sciences > School of Life Sciences
Dewey Decimal Subjects: 500 Science > 570 Life sciences; biology > 572 Biochemistry
500 Science > 550 Earth sciences & geology
500 Science > 570 Life sciences; biology > 570 Life sciences; biology
Library of Congress Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Q Science > QH Natural history > QH301 Biology
G Geography. Anthropology. Recreation > GC Oceanography
Item ID: 1696
Depositing User: RAE Import
Date Deposited: 08 Jul 2008 10:14
Last Modified: 09 Jul 2010 14:27

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