| Summary: | In response to global warming, an increase in cyanobacterial blooms is expected. In this work, the response of two native species of <i>Planktothrix agardhii</i> and <i>Aphanizomenon gracile</i>, as well as the response of two species alien to Europe—<i>Chrysosporum bergii</i> and <i>Sphaerospermopsis aphanizomenoides</i>—to gradual temperature increase was tested. The northernmost point of alien species distribution in the European continent was recorded. The tested strains of native species were favoured at 20⁻28 °C. Alien species acted differently along temperature gradient and their growth rate was higher than native species. Temperature range of optimal growth rate for <i>S. aphanizomenoides</i> was similar to native species, while <i>C. bergii</i> was favoured at 26⁻30 °C but sensitive at 18⁻20 °C. Under all tested temperatures, non-toxic strains of the native cyanobacteria species prevailed over the toxic ones. In <i>P. agardhii</i>, the decrease in concentration of microcystins and other oligopeptides with the increasing temperature was related to higher growth rate. However, changes in saxitoxin concentration in <i>A. gracile</i> under different temperatures were not detected. Accommodating climate change perspectives, the current work showed a high necessity of further studies of temperature effect on distribution and toxicity of both native and alien cyanobacterial species.
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