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13th Biennial Challenger Conference for Marine Science8th -11th September 2008 |
The distribution of net and gross production in the oceans
Michael Bender, Nicolas Cassar, and Rachel Stanley, Department of Geosciences, Princeton University, Princeton, NJ 08544, U. S. A.
Jan Kaiser, School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ
Photosynthesis in the oceans forms the base of the food chain, and net community production (NCP, which is comparable to export production) accounts for the flux of organic matter to the dark ocean and most chemical variability in the sea. Jenkins, Emerson, Quay, Luz and their collaborators have assessed net community production rates in the upper ocean at time series stations from the biological O2 supersaturation (O2 supersaturation in excess of Ar supersaturation) and an estimate of the gas transfer velocity. Luz also pioneered an approach for assessing gross primary production (GPP) from the triple isotope composition of dissolved O2. More recently, we and other groups have complemented this work by assessing NCP and GPP from O2/Ar ratios, and O2 isotopes, measured in discrete samples taken along cruise tracks of volunteer observing ships. In addition, we and Tortell have implemented continuous underway measurements of O2/Ar ratios by membrane inlet (or equilibrator inlet) mass spectrometry. The current data, largely summarized in this talk, give a first order picture, generally consistent with other approaches, of NCP variability in the stratified (spring and summertime) ocean.