NITROGEN FIXATION MEASURED BY STOICHIOMETRIC FLUCTUATIONS
The elemental quotas of carbon, nitrogen, and phosphorus were measured in the 20-200 um size fraction in July 2015 in samples collected from surface waters of an anticyclonic eddy encountered near Hawaii in the oligotrophic North Pacific Subtropical Gyre. The N:P ratio was observed to fluctuate by approximately a factor of two over the diel cycle. Based on this diurnal change, we present a simple mathematical argument to estimate that the rate of nitrogen fixation driven by this size class was >13 nmol N per liter per day, a value consistent with other approaches. Our method represents a novel means for quantification of nitrogen fixation rates from diurnal changes in size-fractionated particulate stoichiometry. We also present estimates of carbon fixation, oxygen generation, specific growth rates, and phosphorus uptake rate for this size class. Importantly, we believe that this method is scalable to allow for continuous estimation of nitrogen fixation rates in oligotrophic regions where diazotrophy is prevalent.
Follett, C. L., MIT, USA, firstname.lastname@example.org
White, A. E., Oregon State University, USA, awhite@COAS.OREGONSTATE.EDU
Follows, M. J., MIT, USA, email@example.com
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