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AME 33:201-205 (2003)
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Abstract
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Heterotrophic nanoflagellates and increased essential fatty acids during Microcystis decay
Sangkyu Park1,5,*, Michael T. Brett2, Dörthe C. Müller-Navarra3, Sang-Cheon Shin4, Anne M. Liston1, Charles R. Goldman1
1Department of Environmental Science and Policy, University of California, 1 Shields Avenue, Davis, California 95616, USA
2Department of Civil and Environmental Engineering, University of Washington, Box 352700, 301 More Hall, Seattle, Washington 98195, USA
3Institut für Hydrobiologie und Fischereiwissenschaft, Abteilung Biologische Ozeanographie, Universität Hamburg, Olbersweg 24, 22767 Hamburg, Germany
4Geyongsangbuk-do Provincial Institute of Health and Environment, Deagu, 702-702, South Korea
5Present address: West Sea Fisheries Research Institute, San 66-3, Eulwang-dong, Jung-gu, Incheon 400-420, South Korea
*Email: daphnia@hitel.net
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ABSTRACT: To investigate the potential for heterotrophic organisms to upgrade the food quality of seston, we performed decay experiments using a non-toxic Microcystis aeruginosa (cyanobacteria) monoculture. The experiment was performed in darkness
with aeration using a microbial inoculum collected from a hypereutrophic pond. Chlorophyll a concentrations decreased throughout the decay experiment. In contrast, eicosapentaenoic acid (EPA, 20:5w3) and docosahexaenoic
acid (DHA, 22:6w3) concentrations increased and peaked on Day 5, while a-linolenic acid (a-LA, 18:3w3) and stearidonic acid (18:4w3) gradually decreased, suggesting that EPA and DHA might be converted from a-LA and stearidonic acid. Microscopic examination revealed that a heterotrophic nanoflagellate (HNF) and the ciliate
Vorticella sp. dominated the biological community during this experiment. Further examination using scanning electron microscopy (SEM) identified the HNF as Paraphysomonas vestita ssp. vestita, whose biovolume was very strongly
correlated with EPA concentrations. Size-fractionized fatty acid determinations carried out on Day 6 showed that approximately two-thirds of the seston's total EPA content was in the <5 µm size fraction, which corresponded to the P. vestita size
fraction. This size fraction also had a fatty acid content (relative to carbon content) 3 times higher than the 5 to 10 or >10 µm seston size fractions.
KEY WORDS: Trophic upgrading · Essential fatty acids · Food quality · Microcystis · Decaying · Paraphysomonas
Full text in pdf format
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Published in AME Vol.
33, No. 2
(2003) on October 14
Print ISSN: 0948-3055; Online ISSN: 1616-1564.
Copyright © Inter-Research, Oldendorf/Luhe, 2003
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