Variability in the organic ligands released by Emiliania huxleyi under simulated ocean acidification conditions

The variability in the extracellular release of organic ligands by Emiliania huxleyi under four different pCO 2 scenarios (225, 350, 600 and 900 μatm), was determined. Growth in the batch cultures was promoted by enriching them only with major nutrients and low iron concentrations. No chelating agen...

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Bibliographic Details
Published in:AIMS Environmental Science
Main Authors: Guillermo Samperio-Ramos, J. Magdalena Santana-Casiano, Melchor González-Dávila, Sonia Ferreira, Manuel A. Coimbra
Format: Article in Journal/Newspaper
Language:English
Published: AIMS Press 2017
Subjects:
Emiliania huxleyi
acidification
extracellular release
phenolic compounds dissolved uronic acids
Environmental sciences
GE1-350
Dua
Ocean acidification
Online Access:https://doi.org/10.3934/environsci.2017.6.788
https://doaj.org/article/8856a3a9b53642a5bb0a1fcc7b68866c
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Summary:The variability in the extracellular release of organic ligands by Emiliania huxleyi under four different pCO 2 scenarios (225, 350, 600 and 900 μatm), was determined. Growth in the batch cultures was promoted by enriching them only with major nutrients and low iron concentrations. No chelating agents were added to control metal speciation. During the initial (IP), exponential (EP) and steady (SP) phases, extracellular release rates, normalized per cell and day, of dissolved organic carbon (DOC ER ), phenolic compounds (PhC ER ), dissolved combined carbohydrates (DCCHO ER ) and dissolved uronic acids (DUA ER ) in the exudates were determined. The growth rate decreased in the highest CO 2 treatment during the IP (＜48 h), but later increased when the exposure was longer (more than 6 days). DOC ER did not increase significantly with high pCO 2 . Although no relationship was observed between DCCHO ER and the CO 2 conditions, DCCHO was a substantial fraction of the freshly released organic material, accounting for 18% to 37%, in EP, and 14% to 23%, in SP, of the DOC produced. Growth of E. huxleyi induced a strong response in the PhC ER and DUA ER . While in EP, PhC ER were no detected, the DUA ER remained almost constant for all CO 2 treatments. Increases in the extracellular release of these organic ligands during SP were most pronounced under high pCO 2 conditions. Our results imply that, during the final growth stage of E. huxleyi , elevated CO 2 conditions will increase its excretion of acid polysaccharides and phenolic compounds, which may affect the biogeochemical behavior of metals in seawater.

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