The Effect Of Environmental Factors On The Growth And Competition Of Chlorella Vulgaris And Anabaenasp.Strain PCC

Chlorella vulgaris is a common freshwater algae and Anabaena sp.strain PCC is one of the most common blue-green algae in eutrophication lakes. The results indicated that:1. C.vulgaris grew best at 35 ? and Anabaena sp.strain PCC grew best between 30-35 ? both in the uni-culture system and the co-culture system. The inhibition parameter of interspecies competition could be significantly influenced by temperature. The maximum inhibition parameter of Anabaena sp.strain PCC against C.vulgaris was found at 15 "C and the number is 0.9111. The maximum inhibition parameter of C.vulgaris against Anabaena sp.strain PCC was found at 30 ? and the number is 18.38. Anabaena sp.strain PCC and C.vulgaris could unstablely coexist in the co-culture system with the 4 temperatures based on the competition model of Lotka-Volterra.2. C.vulgaris grew best at 6600 1x and Anabaena sp.strain PCC grew best between 4400-6600 lx in the uni-culture system. The inhibition parameter of interspecies competition could be significantly influenced by light. The maximum inhibition parameter of Anabaena sp.strain PCC against C.vulgaris was found at 4400 1x. The maximum inhibition parameter of C.vulgaris against Anabaena sp.strain PCC was found at 6600 lx. Anabaena sp.strain PCC and C.vulgaris could unstablely coexist in the co-culture system with 660 lx and 4400 lx and 6600 lx, and C.vulgaris dominated in the co-culture system with 2200 lx based on the competition model of Lotka-Volterra.3. C.vulgaris grew best at the medium high nitrogen and phosphorus ratio(64:1) and Anabaena sp.strain PCC grew best at the medium low nitrogen and phosphorus ratio(32:1) both in the uni-culture system and the co-culture system. The inhibition parameter of interspecies competition could be significantly influenced by nitrogen and phosphorus ratios. The maximum inhibition parameter of Anabaenasp.strain PCC against C.vulgaris was found at low nitrogen and phosphorus ratio(16:1).The maximum inhibition parameter of C.vulgaris against Anabaena sp.strain PCC was found at the medium high nitrogen and phosphorus ratio.The inhibition parameters of C.vulgaris against Anabaena sp.strain PCC were larger than that of Anabaena sp.strain PCC against C.vulgaris at the low and the medium low nitrogen and phosphorus ratios, but was lower at the medium high and the high nitrogen and phosphorus ratios, which meant that the inhibition effects of Anabaena sp.strain PCC on C.vulgaris were stronger than that of C.vulgaris on Anabaena sp.strain PCC at the low and the medium low nitrogen and phosphorus ratios, but the position was reverse at the medium high and the high nitrogen and phosphorus ratios. Anabaena sp.strain PCC dominated in the co-culture system with the low and the medium low nitrogen and phosphorus ratios, and Anabaena sp.strain PCC and C.vulgaris could unstablely coexist in the co-culture system with the medium high and the high nitrogen and phosphorus ratios based on the competition model of Lotka-Volterra.4. C.vulgaris grew best at the high concentration of nitrogen and phosphorus (N=3.6 ?g-mL-1, P=0.5 ?g-mL-1) both in the uni-culture system and the co-culture system. Anabaena sp.strain PCC grew best at the high concentration of nitrogen and phosphorus in the uni-culture system while in the co-culture system the best growth condition is at the medium concentration of high nitrogen and phosphorus (N=0.72 ?g·mL-1, P=0.1 ?g·mL-1). The inhibition parameter of interspecies competition could be significantly influenced by the concentration of nitrogen and phosphorus. The maximum inhibition parameter of Anabaena sp.strain PCC against C.vulgaris was found at the low concentration of nitrogen and phosphorus (N=0.18 ?g·mL-1, P=0.025 ug·mL-1). The maximum inhibition parameter of C.vulgaris against Anabaena sp.strain PCC was found at the medium high nitrogen and phosphorus. Anabaena sp.strain PCC dominated in the co-culture system with the low and the medium high and the high concentration of nitrogen and phosphorus, and Anabaena sp.strain PCC and C.vulgaris could unstablely coexist in the co-culture system with the medium low concentration of nitrogen and phosphorus based on the competition model of Lotka-Volterra.5. C.vulgaris grew best at pH 9.0 and Anabaena sp.strain PCC grew best at pH 9.0 both in the uni-culture system and the co-culture system. The inhibition parameter of interspecies competition could be influenced by pH significantly. The maximum inhibition parameter of Anabaena sp.strain PCC against C.vulgaris was found at pH 6.0 and the number is 1.778. The maximum inhibition parameter of C.vulgaris against Anabaena sp.strain PCC was found at pH 7.0 and the number is 12.91. The inhibition parameters of C.vulgaris against Anabaena sp.strain PCC were larger than that of Anabaena sp.strain PCC against C.vulgaris at each pH, which meant that the inhibition effects of C.vulgaris on Anabaena sp.strain PCC were stronger than that of Anabaena sp.strain PCC on C.vulgaris.6. The orthogonal experiment showed that Chlorella vulgaris grew best at 35 ? under 660 lx while C(N)=0.36 mg·L-1 and C(P)= 0.1 mg·L-1 and pH 9.0; Anabaena sp.strain PCC grew best at 30 ? under 6600 lx while C(N)=0.18 mg·L-1 and C(P)= 0.1 mg·L-1 and pH 7.0 in the uni-culture system. In the co-culture system, the best growth condition of C.vulgaris is at the temperature of 25 ? under 4400 lx while C(N)=0.18 mg·L-1 and C(P)= 0.5 mg·L-1 and pH 6.0; the best growth condition of Anabaena sp.strain PCC is at the temperature of 35 ? under 4400 lx while C(N)=0.36 mg·L-1 and C(P)= 0.5 mg·L-1 and pH 6.0. Light is not the key factor that affects the growth of C.vulgaris, pH is not the key factor that affects the growth of Anabaena sp.strain PCC and Anabaena sp.strain PCC has stronger affinity with nutrient. The inhibition parameter of interspecies competition could be influenced by temperature and light and nutrient and pH significantly. The maximum inhibition parameter of C.vulgaris against Anabaena sp.strain PCC and Anabaenasp.strain PCC against C.vulgaris were both found at 30 ? under 6600 lx while C(N)=0.36 mg·L-1 and C(P)= 0.025 mg-L"1 and pH 8.0 in the competition experiments.