Comparative study of selenium requirements of three phytoplankton species: Gymnodinium catenatum, Alexandrium minutum (Dinophyta) and Chaetoceros cf. tenuissimus (Bacillariophyta) |
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Authors: | Doblin M; Blackburn S; Hallegraeff G |
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Institution: | Department of Plant Science, University of Tasmania, GPO Box 252-55, Tasmania, 7001, Australia; CSIRO Division of Marine Research, GPO Box 1538, Hobart, Tasmania, 7001, Australia; Corresponding author address: Department of Ocean, Earth & Atmospheric Sciences, Old Dominion University, 4600 Elkhorn Avenue, Norfolk, VA 23529-0276, USA |
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Abstract: | This study investigated the selenium (SE) requirements of three
phytoplankton species which commonly bloom in southern Australian
estuaries. The present study showed that the toxic dinoflagellate
Gymnodinium catenatum Graham had an obligate
requirement for Se (IV) in culture. After two transfers ( 4 weeks =
7 generations) in Se-deficient seawater medium, this phytoplankton species
exhibited a decline in growth rate (25%) and biomass yield (90%), while
complete cessation of cell division occurred under prolonged (8 weeks = 12
generations) Se starvation. Addition of
10-9-10-7 M H2SeO3 to
nutrient-enriched seawater medium resulted in increased
G.catenatum growth and biomass yields in direct
proportion to the Se concentrations offered. In contrast to
G.catenatum, Se limitation was observed in the
dinoflagellate Alexandrium minutum Halim after four
transfers (5 weeks = 20 generations) in Se-deficient medium. Exponential
growth rates of A.minutum decreased slightly (5-10%)
when Se was not supplied, but biomass yields decreased as much as 80-90%.
The diatom Chaetoceros cf.
<It>tenuissimus Meunier showed no evidence of Se
limitation even after eight transfers (8 weeks; >60 generations) in
Se-deficient medium. Variations in growth rates and biomass yields between
transfers provide valuable information about the relative potential for Se
limitation in the three species studied. In addition, differences in Se
requirement between these bloom-forming phytoplankton species suggest that
this micronutrient may play a role in structuring phytoplankton communities
in southern Australian waters.
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