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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 2
Biogeosciences, 15, 649–667, 2018
https://doi.org/10.5194/bg-15-649-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Biogeosciences, 15, 649–667, 2018
https://doi.org/10.5194/bg-15-649-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 01 Feb 2018

Research article | 01 Feb 2018

Marine isoprene production and consumption in the mixed layer of the surface ocean – a field study over two oceanic regions

Dennis Booge1, Cathleen Schlundt2, Astrid Bracher3,4, Sonja Endres1, Birthe Zäncker1, and Christa A. Marandino2 Dennis Booge et al.
  • 1GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany
  • 2Marine Biological Laboratory, MBL, Woods Hole, MA, USA
  • 3Alfred Wegener Institute – Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
  • 4Institute of Environmental Physics, University of Bremen, Germany

Abstract. Parameterizations of surface ocean isoprene concentrations are numerous, despite the lack of source/sink process understanding. Here we present isoprene and related field measurements in the mixed layer from the Indian Ocean and the eastern Pacific Ocean to investigate the production and consumption rates in two contrasting regions, namely oligotrophic open ocean and the coastal upwelling region. Our data show that the ability of different phytoplankton functional types (PFTs) to produce isoprene seems to be mainly influenced by light, ocean temperature, and salinity. Our field measurements also demonstrate that nutrient availability seems to have a direct influence on the isoprene production. With the help of pigment data, we calculate in-field isoprene production rates for different PFTs under varying biogeochemical and physical conditions. Using these new calculated production rates, we demonstrate that an additional significant and variable loss, besides a known chemical loss and a loss due to air–sea gas exchange, is needed to explain the measured isoprene concentration. We hypothesize that this loss, with a lifetime for isoprene between 10 and 100 days depending on the ocean region, is potentially due to degradation or consumption by bacteria.

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Our isoprene data from field measurements in the mixed layer from the Indian Ocean and the eastern Pacific Ocean show that the ability of different phytoplankton functional types to produce isoprene seems to be mainly influenced by light, ocean temperature, salinity, and nutrients. By calculating in-field isoprene production rates, we demonstrate that an additional loss is needed to explain the measured isoprene concentration, which is potentially due to degradation or consumption by bacteria.
Our isoprene data from field measurements in the mixed layer from the Indian Ocean and the...
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