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AME 34:93-104 (2004)
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Abstract
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Transparent exopolymer particles and dissolved organic carbon production by Emiliania huxleyi exposed to different CO2 concentrations: a mesocosm experiment
Anja Engel1,*, Bruno Delille2, Stéphan Jacquet3, Ulf Riebesell1, Emma Rochelle-Newall4, Anja Terbrüggen1, Ingrid Zondervan1
1Alfred Wegener Institute for Polar- and Marine Research, 27515 Bremerhaven, Germany
2Unité d'Océanographie Chimique, Université de Liège, 4000 Liège, Belgium
3UMR CARRTEL, Station INRA d'Hydrobiologie Lacustre, 74203 Thonon-les-Bains cedex, France
4Laboratoire d'Océanographie de Villefranche-sur-Mer, 06234 Villefranche-sur-Mer, France
*Email: aengel@awi-bremerhaven.de
ABSTRACT: The role of transparent exopolymer particles (TEP) and dissolved organic carbon (DOC) for organic carbon partitioning under different CO2 conditions was examined during a mesocosm experiment with the coccolithophorid Emiliania
huxleyi. We designed 9 outdoor enclosures (~11 m3) to simulate CO2 concentrations of estimated 'Year 2100' (~710 ppm CO2), 'present' (~410 ppm CO2) and 'glacial' (~190 ppm CO2) environments, and
fertilized these with nitrate and phosphate to favor bloom development. Our results showed fundamentally different TEP and DOC dynamics during the bloom. In all mesocosms, TEP concentration increased after nutrient exhaustion and accumulated steadily
until the end of the study. TEP concentration was closely related to the abundance of E. huxleyi and accounted for an increase in POC concentration of 35 ± 2% after the onset of nutrient limitation. The production of TEP normalized to the cell
abundance of E. huxleyi was highest in the Year 2100 treatment. In contrast, DOC concentration exhibited considerable short-term fluctuations throughout the study. In all mesocosms, DOC was neither related to the abundance of E. huxleyi nor
to TEP concentration. A statistically significant effect of the CO2 treatment on DOC concentration was not determined. However, during the course of the bloom, DOC concentration increased in 2 of the 3 Year 2100 mesocosms and in 1 of the
present mesocosms, but in none of the glacial mesocosms. It is suggested that the observed differences between TEP and DOC were determined by their different bioavailability and that a rapid response of the microbial food web may have obscured
CO2 effects on DOC production by autotrophic cells.
KEY WORDS: Emiliana huxleyi · Transparent exopolymer particles · TEP · Dissolved organic carbon · DOC · Carbon overconsumption · CO2 · Redfield ratios · Mesocosms
Full text in pdf format
Published in AME Vol.
34, No. 1
(2004) on January 16
Print ISSN: 0948-3055; Online ISSN: 1616-1564.
Copyright © Inter-Research, Oldendorf/Luhe, 2004
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