Annual Cycle of Freshwater Diatoms in the High Arctic Revealed by Multiparameter Fluorescent Staining
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MICROBIOLOGY OF AQUATIC SYSTEMS
Annual Cycle of Freshwater Diatoms in the High Arctic Revealed by Multiparameter Fluorescent Staining Eva Hejduková 1
&
Josef Elster 2,3
&
Linda Nedbalová 1,2
Received: 13 January 2020 / Accepted: 1 May 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Diatoms (Bacillariophyceae) are important primary producers in a wide range of hydro-terrestrial habitats in polar regions that are characterized by many extreme environmental conditions. Nevertheless, how they survive periods of drought and/or freeze remains unknown. A general strategy of microorganisms to overcome adverse conditions is dormancy, but morphologically distinct diatom resting stages are rare. This study aimed to evaluate the annual cycle of freshwater diatoms in the High Arctic (Central Spitsbergen) and provide an insight into their physiological cell status variability. The diversity and viability of diatom cells were studied in samples collected five times at four study sites, tracing the key events for survival (summer vegetative season, autumn dry-freezing, winter freezing, spring melting, summer vegetative season [again]). For viability evaluation, a multiparameter fluorescent staining was used in combination with light microscopy and allowed to reveal the physiological status at a single-cell level. The proportions of the cell categories were seasonally and locality dependent. The results suggested that a significant portion of vegetative cells survive winter and provide an inoculum for the following vegetative season. The ice thickness significantly influenced spring survival. The thicker the ice layer was, the more dead cells and fewer other stages were observed. The influence of the average week max–min temperature differences in autumn and winter was not proven. Keywords Diatoms . Life cycle . Overwintering . Freezing tolerance . Viability . Polar regions
Introduction Natural conditions in polar regions are characterized by many extremes that are challenging for any organism. Despite this fact, diatoms (Bacillariophyceae) apparently adapted well and became one of the most abundant algal groups in many polar freshwater and terrestrial habitats [1, 2] where they have to face inhospitable and stressful polar conditions represented by Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00248-020-01521-w) contains supplementary material, which is available to authorized users. * Eva Hejduková [email protected] 1
Department of Ecology, Faculty of Science, Charles University, Viničná 7, 128 44 Prague 2, Czech Republic
2
Institute of Botany of the Czech Academy of Sciences, Dukelská 135, 379 82 Třeboň, Czech Republic
3
Centre for Polar Ecology, Faculty of Science, University of South Bohemia, Na Zlaté stoce 3, 370 05 České Budějovice, Czech Republic
low light and nutrient supply, as well as low temperatures causing recurrent freezing events and irregular liquid water availability [3, 4]. These patterns differ in periodic
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