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CELL-SPECIFIC EXTRACELLULAR PHOSPHATASE ACTIVITY OF DINOFLAGELLATE POPULATIONS IN ACIDIFIED MOUNTAIN LAKES

Authors

  • Jana Novotná,

    1. Department of Ecology, Faculty of Science, Charles University, Viničná 7, CZ-12844, Prague, Czech Republic Institute of Botany AS CR, Dukelská 135, CZ-37982, Třeboň, Czech Republic
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  • Linda Nedbalová,

    1. Department of Ecology, Faculty of Science, Charles University, Viničná 7, CZ-12844, Prague, Czech Republic Institute of Botany AS CR, Dukelská 135, CZ-37982, Třeboň, Czech Republic
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  • Jiří Kopáček,

    1. Department of Ecosystem Biology, Faculty of Science, University of South Bohemia, Branišovská 31, CZ-37005 České Budějovice, Czech Republic Institute of Hydrobiology, Biology Centre AS CR, Branišovská 31, CZ-37005 České Budějovice, Czech Republic
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  • Jaroslav Vrba

    Corresponding author
    1. Department of Ecosystem Biology, Faculty of Science, University of South Bohemia, Branišovská 31, CZ-37005 České Budějovice, Czech Republic Institute of Hydrobiology, Biology Centre AS CR, Branišovská 31, CZ-37005 České Budějovice, Czech Republic
      Author for correspondence: e-mail vrba@hbu.cas.cz.
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  • Received 13 March 2009. Accepted 28 January 2010.

Author for correspondence: e-mail vrba@hbu.cas.cz.

Abstract

High bulk extracellular phosphatase activity (PA) suggested severe phosphorus (P) deficiency in plankton of three acidified mountain lakes in the Bohemian Forest. Bioavailability of P substantially differed among the lakes due to differences in their P loading, as well as in concentrations of aluminum (Al) and its species, and was accompanied by species-specific responses of phytoplankton. We combined the fluorescently labeled enzyme activity (FLEA) assay with image cytometry to measure cell-specific PA in natural populations of three dinophyte species, occurring in all the lakes throughout May–September 2007. The mean cell-specific PA varied among the lakes within one order of magnitude: 188–1,831 fmol · cell−1 · h−1 for Gymnodinium uberrimum (G. F. Allman) Kof. et Swezy, 21–150 fmol · cell−1 · h−1 for Gymnodinium sp., and 22–365 fmol · cell−1 · h−1 for Peridinium umbonatum F. Stein. To better compare cell-specific PA among the species of different size, the values were normalized per unit of cell biovolume (amol · μm−3 · h−1) for further statistical analysis. A step-forward selection identified concentrations of total and ionic Al together with pH as significant factors (< 0.05, Monte Carlo permutation test), explaining cumulatively 57% of the total variability in cell-specific PA. However, this cell-specific PA showed an unexpected reverse trend compared to an overall gradient in P deficiency of the lake plankton. The autecological insight into dinophyte cell-specific PA therefore suggested other factors, such as light availability, mixotrophy, and/or zooplankton grazing, causing further PA variations among the acidified lakes.

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