Biological Productivity in the Northeast Pacific: Comparing an in-situ method with incubation based methods

Date

2013-10-29

Authors

Giesbrecht, Karina

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Abstract

In-situ net community production (NCP) was measured on nine cruises along Line P in the subarctic Northeast Pacific during 2007-2009 and incubation based new, regenerated and carbon production on four cruises starting in August 2008. In-situ NCP, determined using the O2/Ar gas ratio in the mixed layer, averaged 18.4±5.1 mmol O2 m-2 d-1 for stations west of 130°W in June and August. In-situ NCP was nearly equivalent to 24-h 15NO3 - based euphotic zone integrated new production (New-P) with an average NCP: New-P ratio of 1.3±0.4 that was consistent over a range of environmental conditions. The relationship between NCP and 24-h 13C integrated production (C-PP) was variable, but with a consistent mean NCP:C-PP ratio of 0.42±0.27 even when historical measurements were included in the comparison. Two offshore high productivity events were observed in the HNLC region of Line P, one centered between 134°W and 139°W and the other west of 130°W. Only one high productivity event shows conclusive evidence of being caused by iron deposition.

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Keywords

NCP, subarctic, euphotic zone

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