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January
10, 2007 The The title of an
accompanying News
and Views piece says it all, "Looking for [N2] Fixation in all the
Wrong
Places." It's important to
have a global
picture of where nitrogen fixation is occurring – that is
where nitrogen gas is
being converted into substances like nitrate that are usable by life
– in order
to understand the environmental controls on nitrogen fixation and its
likely
response to climate change in the past and in the future, says Curtis
Deutsch,
a University of Washington research assistant and lead author of a
paper in the
January 11 issue of Nature. The new
research, for example, indicates that the inventory of nitrogen in the
oceans
is likely to be less subject to major fluctuations than had been
assumed. Because it has been
thought that
nitrogen fixation is limited without enough iron, the conventional
wisdom for
the past decade dictated that the Winds can't carry
such dust all
the way across the The new research
also means
places where nitrogen is being fixed by certain microorganisms are in
close
proximity to where it is being pulled back apart into its gaseous state
by a
different kind of micoorganism, he says. Nitrogen gas, [N2],
is unusable
by life. It has to be fixed, that is, latched onto other chemicals to
form
compounds such as nitrate, [NO3]. Only then can it be used to build
amino acids
and proteins essential to all life. Eventually the fixed
nitrogen is
returned to its gaseous state, a process called denitrification.
Scientists
have known for several decades that denitrification occurs in the deep,
low-oxygen waters of the Pacific and Indian oceans. If the The new findings
show the
processes are happening within a few hundred miles of each other so the
balance
could be reached within a decade, the authors estimate. Deutsch
compares the
old assumption to a house where the thermostat is many rooms away from
a window
that has swung open, letting in cold air. The house could get quite
chilly
before the draft reaches the thermostat and the furnace turns on. But
if the
thermostat is in the same room as the window, the furnace will turn on
and even
out the temperature much faster. In his research
Deutsch used a
novel analysis of surface nutrients in the world's oceans that relied
on
several decades of existing large-scale data on nitrogen-to-phosphorous
ratios,
phosphorous also playing a major role in primary production. His work
has been
supported by a NASA Earth System Science Fellowship and the UW Program
on
Climate Change. "There has been a
great deal
of controversy in the literature as to whether fixed nitrogen in the
ocean
remains constant with time or fluctuates widely," says Jorge Sarmiento,
professor of geosciences at
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