Net and gross production in the Ross Sea as determined by incubation experiments and dissolved O-2 studies

We report net and gross production rates for samples from three JGOFS cruis es to the Ross Sea during spring-autumn 1996-1997. We summarize continuous electrode measurements of mixed-layer O-2 supersaturation taken during Janu ary 1997, and use these to calculate air-sea O-2 fluxes and upper ocean net production. We also calculate net production rates from changes in the 0-8 0 m inventories of dissolved nitrate. Net C production rates during summer (January-February 1997), inferred from bottle incubations and O-2 supersatu ration, are 60 and 56 mmol m(-2) day(-1), respectively. These values agree well with net production values from November 1 to February 6 estimated fro m the decrease in the nitrate inventory of the upper water column, 108 mmol m(-2) day(-1). Depth-integrated gross C production measured on the summer cruise averaged 185 mmol m(-2) day(-1). High values of net C production, gr oss C production, and net/gross ratio (0.32) confirm earlier studies (e.g., Smith and Gordon, Geophysical Research Letters 24 (1997) 233-236) concludi ng that net and gross rates of carbon production are very high during the s pring and summer. delta O-18 values of dissolved O-2 also demonstrate that C and O-2 are rapidly cycled metabolically even when mixed-layer O-2 concen trations are close to saturation. (C) 2000 Published by Elsevier Science Lt d.