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| Titel |
Selenium Uptake and Volatilization by Marine Algae |
| VerfasserIn |
Katja E. Luxem, Bas Vriens, Bettina Wagner, Renata Behra, Lenny H. E. Winkel |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106930
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| Publikation (Nr.) |
 EGU/EGU2015-6613.pdf |
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| Zusammenfassung |
| Selenium (Se) is an essential trace nutrient for humans. An estimated one half to one billion
people worldwide suffer from Se deficiency, which is due to low concentrations and
bioavailability of Se in soils where crops are grown. It has been hypothesized that more than
half of the atmospheric Se deposition to soils is derived from the marine system, where
microorganisms methylate and volatilize Se. Based on model results from the late 1980s, the
atmospheric flux of these biogenic volatile Se compounds is around 9 Gt/year, with two thirds
coming from the marine biosphere.
Algae, fungi, and bacteria are known to methylate Se. Although algal Se uptake,
metabolism, and methylation influence the speciation and bioavailability of Se in the oceans,
these processes have not been quantified under environmentally relevant conditions and are
likely to differ among organisms. Therefore, we are investigating the uptake and methylation
of the two main inorganic Se species (selenate and selenite) by three globally relevant
microalgae: Phaeocystis globosa, the coccolithophorid Emiliania huxleyi, and the diatom
Thalassiosira oceanica.
Selenium uptake and methylation were quantified in a batch experiment, where parallel
gas-tight microcosms in a climate chamber were coupled to a gas-trapping system. For E.
huxleyi, selenite uptake was strongly dependent on aqueous phosphate concentrations,
which agrees with prior evidence that selenite uptake by phosphate transporters is a
significant Se source for marine algae. Selenate uptake was much lower than selenite
uptake. The most important volatile Se compounds produced were dimethyl selenide,
dimethyl diselenide, and dimethyl selenyl sulfide. Production rates of volatile Se
species were larger with increasing intracellular Se concentration and in the decline
phase of the alga. Similar experiments are being carried out with P. globosa and T.
oceanica.
Our results indicate that marine algae are important for the global cycling of Se,
especially in low phosphate regimes such as oligotrophic waters and late stage phytoplankton
blooms. |
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