EFFECTS OF HARVEST STAGE AND LIGHT ON THE BIOCHEMICAL COMPOSITION OF THE DIATOM THALASSIOSIRA PSEUDONANA1

Authors

  • Malcolm R. Brown,

    Corresponding author
    1. CSIRO Division of Fisheries, GPO Box 1538, Hobart, Tasmania 7001, Australia
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  • Graeme A. Dunstan,

    1. CSIRO Division of Oceanography, GPO Box 1538, Hobart, Tasmania 7001, Australia
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  • Suzanne. J. Norwood,

    1. CSIRO Division of Fisheries, GPO Box 1538, Hobart, Tasmania 7001, Australia
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    • 3

      Department of Agricultural Science, University of Tasmania, GPO Box 252C, Hobart, Tasmania 7001, Australia.

  • Kelly A. Miller

    1. CSIRO Division of Fisheries, GPO Box 1538, Hobart, Tasmania 7001, Australia
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      Department of Biochemistry, University of Tasmania, GPO Box 252C, Hobart, Tasmania 7001, Australia.


  • 1

    Received 5 July 1995. Accepted 11 October 1995.

  • We thank Drs. P. D. Nichols and P. A. Thompson for commenting on an earlier version of the manuscript. This work was supported by the Fisheries Research and Development Corporation (Grants 90/63 and 91/59).

Author for reprint requests.

ABSTRACT

The marine diatom Thalassiosira pseudonana (Hustedt, clone 3H) Hasle and Heimdal was cultured under three different light regimes: 100 μmol photon · m−2· s−1 on 12:12 h light : dark (L:D) cycles; 50 μmol photon · m−2· s−2 on 24:0 h L:D; and 100 μmol photon · m−2· s−1 on 24:0 h L:D. It was harvested during logarithmic and stationary phases for analysis of biochemical composition. Across the different light regimes, protein (as % of organic weight) was highest in cells during logarithmic phase, whereas carbohydrate and lipid were highest during stationary phase. Carbohydrate concentrations were most affected by the different light regimes; cells grown under 12:12 h L:D contained 37–44% of the carbohydrate of cells grown under 24:0 h L:D. Cells in logarithmic phase had high proportions of polar lipids (79 to 89% of total lipid) and low triacylglycerol (≤10% of total lipid). Cells in stationary phase contained less polar lipid (48 to 57% of total lipid) and more triacylglycerol (22 to 45% of total lipid). The fatty acid composition of logarithmic phase cells grown under 24:0 h L:D were similar, but the 100 μmol photon · m−2· s−1 (12:12 h L:D) cells at the same stage contained a higher proportion of polyunsaturated fatty acids (PUFAs) and a lower proportion of saturated and monounsaturated fatty acids due to different levels of 16:0, 16:1(n-7), 16:4(n-1), 18:4(n-3), and 20:5(n-3). With the onset of stationary phase, cells grown at 100 μmol photon · m−2· s−1 (both 12:12 and 24:0 h L:D) increased in proportions of saturated and monounsaturated fatty adds and decreased in PUFAs. Concentrations (% organic or dry weight) of 14:0, 16:0, 16:1(n-7), 20:5(n-3), and 22:6(n-3) increased in cells of all cultures during stationary phase. The amino acid compositions of cells were similar irrespective of harvest stage and light regime. For mariculture, the recommended light regime for culturing T. pseudonana will depend on the nutritional requirements of the animal to which the alga is fed. For rapidly growing bivalve mollusc larvae, stationary-phase cultures grown under a 24:0 h L:D regime may provide more energy by virtue of their higher percentage of carbohydrate and high proportions and concentrations of energy-rich saturated fatty acids.

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