This review has discussed the controls of the oxygen isotope ratios in
atmospheric CO
and O
and in the O
/N
ratio and how
measurements of these quantities can be used to study the material
exchanges with biota over large areas. Measurements of the
O/
O ratio of atmospheric CO
can provide information on
stomatal conductance and gross primary production of terrestrial
ecosystems. Measurements of variations in the 
O/
O ratio of
atmospheric O
can provide information on variations in the isotopic
composition of globally averaged metabolic water, which is linked to the
ratio of gross primary production on land versus the ocean. Measurements
of the O
/N
ratio can provide information on net rates of carbon
storage or release from the terrestrial biosphere and on rates of carbon
fixation in the ocean.
I thank Joe Berry for first articulating to me the idea of using
O in CO
for constraining GPP and stomatal conductances. This
work has been supported by the Environmental Protection Agency
Global Change Research Program, IAG#DW49935603-01-2, and the
National Science Foundation under grant ATM-9309765.