Salinity tolerance in biogeographically different strains of the marine benthic diatom Cylindrotheca closterium (Bacilla
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Salinity tolerance in biogeographically different strains of the marine benthic diatom Cylindrotheca closterium (Bacillariophyceae) Karin Glaser 1 & Ulf Karsten 1 Received: 28 April 2020 / Revised and accepted: 18 August 2020 # Springer Nature B.V. 2020
Abstract In coastal zones, salinity is commonly a rather local environmental factor that can be highly variable. Future climate change scenarios indicate for many coastal regions besides warming also changes in current salinity regime due to less precipitation, higher evaporation, or more freshwater run-off, resulting in decreasing or increasing saline conditions. The soft bottom of shallow water coastal zones is typically inhabited by benthic diatoms which cover as photosynthetic biofilms extensive areas of sediments. Cylindrotheca closterium is a cosmopolitan and abundant taxon of such communities, and is widely used as a benthic diatom model system. Nevertheless, comprehensive ecophysiological data on the salinity tolerance of this ecologically important benthic species are still missing. Therefore, the main goal was to investigate the salinity tolerance in 6 strains of C. closterium from 5 different clades and from marine to brackish habitats. An analysis of growth as function of salinity allowed the evaluation of tolerance limits, growth optima, and acclimation abilities of individual strains. The data documented isolate-specific growth response patterns and rather broad tolerance widths among the six strains of C. closterium, which point to strong genotypic differentiation. The results of the phylogenetic network analysis indicate several well separated grades within C. closterium, thereby supporting the earlier suggestion of a cryptic species complex. Keywords Cylindrotheca closterium . Benthic diatom . Growth . Salinity tolerance
Introduction Physiological performance, biogeographic distribution, and biodiversity of micro- and macroalgae are primarily controlled by various environmental factors such as salinity. The salt concentration and composition is almost constant throughout the open oceans due to intensive mixing, and it varies only between 33 and 37 SA (absolute salinity SA: mass fraction of salt in seawater, g dissolved salts kg−1 water, Wright et al. 2010). In estuaries and near-shore waters, however, where river freshwater mixes with marine water bodies, salinity typically shows strong fluctuations. Here, vertical and horizontal gradients between 0 and 33 SA can be observed. Other processes such as hydrological conditions, tidal flows, precipitation, wind, and Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10811-020-02238-6) contains supplementary material, which is available to authorized users. * Ulf Karsten [email protected] 1
University of Rostock, Institute of Biological Sciences, Albert-Einstein-Strasse 3, 18057 Rostock, Germany
evaporation strongly influence the salt content of the respective water body. Consequently, salinity is typically a local rather than a global parameter and
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