Continuous measurements of dissolved O-2 and oxygen isotopes in the Southern California coastal ocean

TitleContinuous measurements of dissolved O-2 and oxygen isotopes in the Southern California coastal ocean
Publication TypeJournal Article
Year of Publication2015
AuthorsRafelski LE, Paplawsky B, Keeling RF
JournalMarine Chemistry
Date Published2015/08
Type of ArticleArticle
ISBN Number0304-4203
Accession NumberWOS:000358628600010
Keywordsaquatic ecosystems; atmospheric oxygen; Dissolved gases; Diurnal variations; fractionation; inlet mass-spectrometry; Mass spectrometer; oxygen isotopes; photosynthesis; productivity; respiration rates; sea; spaced data; stable-isotopes; water

Dissolved O-2/N-2, O-2/Ar, O-2 saturation and delta O-18 were measured continuously near the surface ocean at the Scripps Institution of Oceanography pier in La Jolla, California, for five weeks. The data showed diurnal cycles, in O-2 and delta O-18, with amplitudes of 19 mmol m(-3) and 1.1%., respectively. The diurnal cycles are well described by a box model that includes photosynthesis, respiration, air-sea gas exchange, and mixing. The timing of the cycles can be explained using a photosynthesis rate proportional to photosynthetically active radiation, and the shapes of the cycles can be explained by mixing with a subsurface layer of water that is supersaturated in O-2. Based on the diurnal cycles in O-2 and delta O-18, the average maximum daily photosynthesis rate was 3.7-4.7 mmol O-2 m(-3) h(-1), which is supported by the light-saturated photosynthesis rate estimated from the measured chlorophyll concentration. In the future, these continuous measurement techniques could be used at different locations and depths to improve the understanding of variability in oceanic primary production. (C) 2015 Elsevier B.V. All rights reserved.

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