Optimization Of Three Useful Algae Culture Conditions And Initial Study Of Interspecific Competition Mechanisms

Microalgae is a primary producer in water,which can effectively carry out photosynthesis,and improve the water environment by converting harmful substances into organic compounds,like ammonia nitrogen,nitrite,and hydrogen sulfide.Microalgae can provide biological feed for aquatic animals,thereby playing an important role in the aquaculture industry.The purpose of this experiment is to determine the optimal culture conditions of three beneficial algae,including temperature,light,pH,nutrient concentration,and study their interspecies competition mechanism,so as to provide high-density cultivation of beneficial algae and multi-algae conditioning Water quality provides data reference.The experiment mainly used the single factor test,Plackett-Burman test and Box-Behnken test to conduct research.The results are as followed:This is the optimal culture conditions for C.vulgaris: 25 ?,light intensity 5000 lux and pH 7.Based on the BG11 medium,three significant factors NaHCO₃,KH₂PO₄ and NaNO₃ were obtained by Plackett-Burman test.The medium composition was optimized by response surface methodology: NaNO₃ 550 mg/L,KH₂PO₄ 60 mg /L,NaHCO₃ 80 mg/L,C₆H₈FeNO₇ 6mg/L,MgSO₄ 75 mg/L,CaCl₂ 36 mg/L,C₆H₈O₇ 6 mg/L and A5 solution 1 m L/L.Using the optimized culture conditions to cultivate C.vulgaris for 15 days,the cell density was 45.65%higher than that in the BG11 medium.This is the optimal culture conditions for O.elliptica: 25 ?,light intensity 5000 lux and pH 8.Based on the BG11 medium,three significant factors obtained by Plackett-Burman test were NaNO₃,KH₂PO₄ and NaHCO₃.The medium composition was optimized: NaNO₃ 300mg/L,KH₂PO₄ 20 mg /L,NaHCO₃ 80 mg/L,C₆H₈FeNO₇ 6 mg/L,MgSO₄ 75 mg/L,CaCl₂ 36mg/L,C₆H₈O₇ 6 mg/L and A5 solution 1 m L/L.Using the optimized culture conditions to cultivate O.elliptica for 15 days,the cell density was 47.13% higher than that in the BG 11 medium.This is the optimal culture condition for N.palea: 20 ?,light intensity 2000 lux and pH8.Based on the CSI medium,three significant factors obtained by Plackett-Burman test were NaSiO₃,NaNO₃ and KH₂PO₄.The optimized medium composition is NaNO₃ 300 mg/L,KH₂PO₄ 20 mg/L,NaHCO₃ 80 mg/L,C₆H₈FeNO₇ 6 mg/L,MgSO₄ 75 mg/L,CaCl₂ 36 mg/L,C₆H₈O₇ 6 mg/L and PIV solution 1m L/L.Through the 15 days culture,the cell density was80.51% higher than that in the CSI medium.When two species of algae were co-cultured in pairs,the average inhibiting effect of N.palea on C.vulgaris was 7.08 times than reverse and on O.elliptica was 1.44 times thanreverse.The average inhibiting effect of O.elliptica on C.vulgaris was 8.85 times than reverse.When the three species of algae were co-cultured,the average inhibitory effect of C.vulgaris on N.palea was 39.75 times than reverse and on O.elliptica was 1.98 times than reverse.The average inhibiting effect of N.palea on O.elliptica was 1.71 times than reverse.