Abstract
Interaction effects of temperature, light, nutrients, and pH on growth and competition of Chlorella vulgaris and Anabaena sp. strain PCC were evaluated using an orthogonal design method to elucidate how these environment factors promote the growth of beneficial algae and limit the growth of harmful algae. The optimal conditions for the growth of C. vulgaris in the mono-culture system were as follows: temperature, 35°C; light, 660 lx; N concentration, 0.36 mg L−1; P concentration, 0.1 mg L−1; and pH, 9.0; and those for Anabaena were as follows: temperature, 30°C; light, 6,600 lx; N concentration, 0.18 mg L−1; P concentration, 0.1 mg L−1; and pH, 7.0. The optimal conditions for the growth of C. vulgaris in the co-culture system were as follows: temperature, 25°C; light, 4,400 lx; N concentration, 0.18 mg L−1; P concentration, 0.5 mg L−1; and pH, 6.0; and those for Anabaena were as follows: temperature, 35°C; light, 4,400 lx; N concentration, 0.36 mg L−1; P concentration, 0.5 mg L−1; and pH, 6.0. Both competition-inhibition parameters of Anabaena against C. vulgaris and those of C. vulgaris against Anabaena were the largest under the following conditions: temperature, 30°C; light intensity, 6,600 lx; N concentration, 0.36 mg L−1; P concentration, 0.025 mg L−1; and pH, 8.0. According to the Lotka–Volterra competition model, Anabaena won in the competition in the co-culture system with the following conditions: 1) temperature, 15°C; light, 660 lx; total N (TN), 0.18 mg L−1; total P (TP), 0.025 mg L−1; pH, 6; 2) temperature, 15°C; light, 2,200 lx; TN, 0.36 mg L−1; TP, 0.025 mg L−1; pH, 7; 3) temperature, 15°C; light, 6,600 lx; TN, 3.6 mg L−1; TP, 0.5 mg L−1; pH, 9; 4) temperature, 30°C; light, 4,400 lx; TN, 0.18 mg L−1; TP, 0.05 mg L−1; pH, 9; 5) temperature, 35°C; light, 660 lx; TN, 3.6 mg L−1; TP, 0.05 mg L−1; pH, 8; and 6) temperature, 35°C; light, 2,200 lx; TN, 0.72 mg L−1; TP, 0.025 mg L−1; pH, 9. However, C. vulgaris could not win in the competition in the co-culture system under all conditions tested.
Highlights
Harmful cyanobacterial blooms are becoming increasingly common in eutrophic water bodies, and they may result in a wide range of environmental, social, and economic consequences
Our analyses showed that the maximum cell density of C. vulgaris increased with temperature (Supplementary Figure S1) and reached the peak point at 35°C
Song et al (2013) observed an apparent exponential growth phase of Chlorella when the temperature increased to 20°C or 25°C, and its specific growth rate and maximum cell density increased with the increase in temperature
Summary
Harmful cyanobacterial blooms are becoming increasingly common in eutrophic water bodies, and they may result in a wide range of environmental, social, and economic consequences. The social and economic effects of cyanobacterial blooms include negative effects on recreational opportunities due to the closure of affected areas, declining local fisheries, and increased water treatment costs (Hoagland et al, 2002; Paerl, 2008). In addition to their wider ecological effects, cyanobacteria are known to produce a suite of secondary metabolites that include hepatotoxins, neurotoxins, and dermatotoxic compounds. These toxins have been linked to reduced water quality and detrimental effects at higher trophic levels (Leonard and Paerl, 2005; Ferrão-Filho et al, 2009), small-animal illness and even mortality (Boyer, 2007; Jacoby and Kann, 2007), and adverse health risks in humans (Paerl, 2008)
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