Determining primary production from the mesoscale oxygen field

Steven Emerson, Paul Quay, Charles Stump, David Wilbur, and Rebecca Schudlich

School of Oceanography WB-10, University of Washington, Seattle, WA 98195, USA

Abstract

Net biological oxygen production can be determined from models of time-series measurements of the oxygen field. so long as there are simultaneous measurements of inert gas tracers to estimate the role of air-water transfer and mixing with the ocean interior. In the two locations where this has been done, the oxygen balance yields net nutrient production values that are within a factor of three of sediment trap and in vitro incubation experiments. Initial findings from a similar study at the US JGOFS time-series station near Hawaii (Station ALOHA) reveal that nitrogen uptake determined by net biological O₂ production in the upper 175 m, which includes both the euphoric and shallow respiration zones. agrees to within a factor of two of the mean annual sediment trap N flux at 150 m. Poorly known processes that should be explored to reconcile differences in the various methods are: (a) transport of dissolved and suspended particulate organic matter out of the euphotic zone, (b) alteration of O₂:DIC:NO₃^- stoichiometry in the euphotic zone by production of carbon-rich dissolved organic matter. and (c) bacterial heterotrophic NO₃^- uptake.