Net community production in the North Atlantic Ocean derived from Volunteer Observing Ship data

Clare Ostle,Peter Landschützer,Susan Hartman,Tom Hull,Carol Robinson,Martin Johnson,Ute Schuster

doi:10.1002/2014gb004868

Abstract

AbstractThe magnitude of marine plankton net community production (NCP) is indicative of both the biologically driven exchange of carbon dioxide between the atmosphere and the surface ocean and the export of organic carbon from the surface ocean to the ocean interior. In this study the seasonal variability in the NCP of five biogeochemical regions in the North Atlantic was determined from measurements of surface water dissolved oxygen and dissolved inorganic carbon (DIC) sampled from a Volunteer Observing Ship (VOS). The magnitude of NCP derived from dissolved oxygen measurements (NCP) was consistent with previous geochemical estimates of NCP in the North Atlantic, with an average annual NCP of 9.5 ± 6.5 mmol O2 m−2 d−1. Annual NCP did not vary significantly over 35° of latitude and was not significantly different from NCP derived from DIC measurements (NCPDIC). The relatively simple method described here is applicable to any VOS route on which surface water dissolved oxygen concentrations can be accurately measured, thus providing estimates of NCP at higher spatial and temporal resolution than currently achieved.

Highlights

The global cycling of oxygen and carbon is regulated by the interactions between oceanic physical and biogeochemical processes including mixing and plankton respiration and photosynthesis
Not globally applicable due to regional variability in horizontal temperature gradients that can influence the solubility of oxygen, preliminary data collected in the Western English Channel suggest little difference between estimates of net community production (NCP) derived from measurements of Ar/O2 and those derived from optode measurements of dissolved oxygen [Gloël, 2012]
Seasonal Cycle of NCPO2 Monthly mean NCPO2 was calculated for each month between December 2011 and March 2013 for each biogeochemical region shown in Figure 2, from the daily time step quasi-1-D model and the calculations described above (see equations (1)–(8)), and is shown in Figure 3 together with mean monthly Chl a data and oxygen saturation

Summary

Introduction

The global cycling of oxygen and carbon is regulated by the interactions between oceanic physical and biogeochemical processes including mixing and plankton respiration and photosynthesis. The concentrations of O2 and CO2 are further influenced by physical processes including bubble injection [Woolf and Thorpe, 1991], and mixing of deep, often oxygen deplete and CO2 replete waters into the mixed layer with associated increased nutrient concentrations stimulating biological production. Heterotrophic oxidation (respiration) leads to the production of dissolved inorganic carbon (DIC), whereas autotrophy (photosynthesis) leads to a reduction of DIC [Falkowski, 1998]. Net community production (NCP) (in the sense of Williams [1993]) indicates the balance between production of organic carbon by autotrophs (P) and production of CO2 by heterotrophs (R) at the time scale and space scale of the measurement technique used [Serret et al, 2009]. The metabolic state of a system can be defined by NCP (= P − R), with autotrophic systems occurring when gross primary production is greater than respiration and heterotrophic systems occurring when respiration is greater than primary production [Ducklow and Doney, 2013]

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Discussion

Conclusion