biogeochemical cycling – fall 2010
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Biogeochemical Cycling – Fall 2010
Theme
Modern Changes in the Nitrogen Cycle
Friday Discussion GroupDiscussion Leader: Priya Ganguli12 November, 2010
• N 5th most abundant element in solar system• Essential for synthesis of nucleic acids and proteins• For every 100 atoms of C in cells, need 2 to 20 atoms of N• Biogeochemistry of N primarily oxidation-reduction and microbially mediated• Secondarily influenced by long-term cycling through geosphere• N2 largely unavailable to organisms• NO3
- and HN4+ (fixed forms) often limit primary productivity in both marine &
terrestrial ecosystems
Nitrogen Fixation
prokaryotes in bacterial and
archaeal domains
reduce N2 gas to ammonium
ion (NH4+)
from Baker MA, Dahm CN, Valett HM, 2000
elec
tron
acc
epto
rs
nitrate (NO3-)
reduction coupled to anaerobic
oxidation of Corg
N2 gas(denitrification)
or
NH4+
(dissimilatory nitrate reduction to ammonium)
(DNRA)
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