Interaction Effects of Temperature, Light, Nutrients, and pH on Growth and Competition of Chlorella vulgaris and Anabaena sp. Strain PCC

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.