Effect of temperature and light on the toxicity and growth of the blue-green alga Microcystis aeruginosa (UV-006)

Abstract

The toxicity and growth of Microcystis aeruginosa (UV-006) from the Hartbeespoort Dam, South Africa were investigated at different temperatures and photon fluence rates under laboratory conditions. Cells harvested in late logarithmic growth phase were most toxic when grown at 20°C (LD50) median lethal dose [IP, mouse]=25.4 mg kg(-1)). Toxicity was markedly reduced at growth temperatures above 28° C. Fluence rate had a smaller effect on the toxicity of the cells, but toxicity tended to be less at the very low and high light fluences. Optimal conditions for growth did not coincide with those for toxin production. Well-aerated cultures of this isolate kept at pH 9.5 by CO2 addition, a temperature of 20-24° C, a fluence rate of 145 μmol photons m(-2) s(-1) and harvested in the late logarithmic growth phase yielded the maximum quantity of toxin.

Mathematical modeling of Microcystis aeruginosa growth and [D-Leu1] microcystin-LR production in culture media at different temperatures

“…The production of [D-Leu 1 ] MC-LR decreased with increasing temperature, coinciding with the findings of Gorham, 1964;Runnegar et al, 1983;van der Westhuizen and Eloff, 1985;Cood and Poon, 1988;Sivonen, 1990;Rapala et al, 1997;Lehman et al, 2008;Wang et al, 2010 andGiannuzzi et al (2016). van der Westhuizen and Eloff (1985) reported that the optimal growth conditions do not coincide with the production of toxins.…”

“…van der Westhuizen and Eloff (1985) reported that the optimal growth conditions do not coincide with the production of toxins. Similarly, Gorham (1964) affirmed that the optimum temperature for growth (30 C -35 C) differed from that for optimal toxicity (25 C).…”

“…Increased water temperature is expected to give cyanobacteria a selective advantage over competing phytoplankton because of the high optimal growth temperature of cyanobacterial species (Elliott et al, 2006;Jöhnk et al, 2008). Laboratory studies on Microcystis aeruginosa have demonstrated increasing growth rates with increasing temperatures from 20 to 32 C (van der Westhuizen and Eloff, 1985;Watanabe and Oishi, 1985;Imai et al, 2009). Robarts and Zohary (1987) found that temperatures of 25-35 C resulted in the highest growth rates of bloom-forming cyanobacteria, including Microcystis.…”

“…Laboratory studies have shown that the toxicity (LD 50 , mg dry algae kg À1 mice) of temperate strains of M. aeruginosa were highest at 18-20 C, and decreased greatly as the temperature increased above 28 C (van der Westhuizen and Eloff, 1985;Watanabe and Oishi, 1985). Culture-based studies have shown that MC concentrations are generally highest between 20 and 25 C (van der Westhuizen and Eloff, 1985;van der Westhuizen et al, 1986;Codd and Poon, 1988;Amé and Wunderlin, 2005).…”

Late-summer phytoplankton in western Lake Erie (Laurentian Great Lakes): bloom distributions, toxicity, and environmental influences

“…Given that secondary metabolites are produced by diverse cyanobacteria encompassing varied ecological niches, it is plausible that microcystin synthesis is associated with and/or regulated by environmental factors affecting cell metabolism, growth, and ultimately, abundance . Reports that state microcystin production and/ or cell quota are influenced by select abiotic parameters, including temperature, irradiance, macro/micronutrients, and pH (van der Westhuizen and Eloff 1985;Lukac and Aegerter 1993;Song et al 1998;Downing et al 2005), support this premise.…”