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Marine nitrogen fixers mediate a low latitude pathway for atmospheric CO2 drawdown.


ABSTRACT: Roughly a third (~30?ppm) of the carbon dioxide (CO2) that entered the ocean during ice ages is attributed to biological mechanisms. A leading hypothesis for the biological drawdown of CO2 is iron (Fe) fertilisation of the high latitudes, but modelling efforts attribute at most 10 ppm to this mechanism, leaving ~20?ppm unexplained. We show that an Fe-induced stimulation of dinitrogen (N2) fixation can induce a low latitude drawdown of 7-16?ppm CO2. This mechanism involves a closer coupling between N2 fixers and denitrifiers that alleviates widespread nitrate limitation. Consequently, phosphate utilisation and carbon export increase near upwelling zones, causing deoxygenation and deeper carbon injection. Furthermore, this low latitude mechanism reproduces the regional patterns of organic ?15N deposited in glacial sediments. The positive response of marine N2 fixation to dusty ice age conditions, first proposed twenty years ago, therefore compliments high latitude changes to amplify CO2 drawdown.

SUBMITTER: Buchanan PJ 

PROVIDER: S-EPMC6787065 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Marine nitrogen fixers mediate a low latitude pathway for atmospheric CO<sub>2</sub> drawdown.

Buchanan Pearse J PJ   Chase Zanna Z   Matear Richard J RJ   Phipps Steven J SJ   Bindoff Nathaniel L NL  

Nature communications 20191010 1


Roughly a third (~30 ppm) of the carbon dioxide (CO<sub>2</sub>) that entered the ocean during ice ages is attributed to biological mechanisms. A leading hypothesis for the biological drawdown of CO<sub>2</sub> is iron (Fe) fertilisation of the high latitudes, but modelling efforts attribute at most 10 ppm to this mechanism, leaving ~20 ppm unexplained. We show that an Fe-induced stimulation of dinitrogen (N<sub>2</sub>) fixation can induce a low latitude drawdown of 7-16 ppm CO<sub>2</sub>. Thi  ...[more]

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