Respiration, mineralization, and biochemical properties of the particulate matter in the southern Nansen Basin water column in April 1981

12 pages, 4 figures, 5 tablesDeterminations of the activity of the respiratory electron transport system (ETS), during the FRAM III expedition permit us to estimate oxygen utilization rates (RO2) from the surface to 2000 m under the polar pack ice in the Nansen Basin just north of Svalbard (83°N, 7°E) during April 1981. We found RO2 at in situ temperatures ranging from 20 pM O2 min-1 just below the ice to 0.2 pM O2 min-1 at 2000 m. These rates are low compared to most other ocean regions, but they could decrease particulate organic carbon and nitrogen by 76% and 74%, respectively, over a period of ∼6 months. The RO2 calculations based on measurements made at 0 °C yielded a power function of RO2 vs. depth (Z) of RO2=67Z-0.5534. When this RO2 profile was superimposed on a more recent oxygen utilization rate profile made using the 3He-3H-AOU method (OUR), in the same vicinity of the Nansen Basin during 1987 (OUR=52Z-0.4058, [Zheng, Y., Schlosser, P., Swift, J.W., Jones, E.P., 1997. Oxygen utilization rates in the Nansen Basin, Arctic Ocean: implications for new production. Deep Sea Research I 44, 1923-1943]), the agreement of the two profiles was close. On one hand, this was to be expected because RO2 is the biological basis of OUR, on the other hand, it was a surprise because the methodologies are so different. Nitrate mineralization obtained from ETS activities also compared favorably with calculations based on the data of Zheng et al. [1997. Oxygen utilization rates in the Nansen Basin, Arctic Ocean: implications for new production. Deep Sea Research I 44, 1923-1943]. Chlorophyll ranged from 6 ng L-1 at 5 m to 0.06 ng L-1 at 2000 m. Particulate organic carbon (POC) decreased from 0.93 μM C just below the ice to less than 0.4 μM C at 500 m. Particulate organic nitrogen (PON) was not detectable below 70 m, however in the upper 70 m it ranged from 0.16 to 0.04 μM N. The C/N mass ratio over these depths ranged from 5.8 to 11.3. Annual carbon productivity as calculated to balance the total water column respiration was 27 g C m-2 y-1. The integrated respiration rate between 50 and 4000 m suggests that exported production and carbon flux from the 50 m level was 24 g C m-2 y-1. These are minimal estimates for the southern Nansen Basin because they are based on measurements made at the end of the Arctic winter. © 2007 Elsevier Ltd. All rights reservedWe acknowledge Institut Ciències del Mar (CSIC), CICYT project MAR98-0932, BIOHAB project EVK3-1999-00072, TURFIREN2002-01591/Mar), MICROROL (CICYT LTM 2004-02575/Mar), and NSF Grants DPP-825744, OPP-0125399 (J. Swift, PI) and OPP-0125306 for financial support. This is contribution No. 200510 from the Bigelow Laboratory from Ocean Sciences. ReferencesPeer Reviewe