Study On Concentration And Preservation Of Three Kinds Of Commonly Used Bait Microalgae

The chemical flocculants including alum, ferric chloride and bait microalgaes in shellfish aquaculture including Isochrysis galbana, Platymonas subcordiformis and Pyramimonas sp. were mainly used to research the following several aspects:(1) By measuring the flocculating efficiency on cells of alum, ferric chloride on algal, the survival rate and the specific growth rate of algal cells after flocculation,and observing the cell morphology, the study researched the effect of the common chemical flocculant on bait microalgae. The results showed that, for Isochrysis galbana, concentration of alum, ferric chloride respectively less than 200mg/L,60mg/mL, for Platymonas subcordiformis and Pyramimonas sp., concentration of alum, ferric chloride respectively less than 120mg/L,30mg/L, had very good flocculating efficiency on bait microalgae above, and couldn’t destroy the structural integrity of algal cells. Algal also could keep the good survival rate and the ability to recovery growth.(2) By measuring the protein, polysaccharide, total lipid, chlorophyll contents of bait microalgae above after flocculated by a certain concentration of alum, ferric chloride and the survival rate and the daily growth rate of Coelomactra antiquata which had been fed with bait microalgae above, the effect of the chemical flocculantson the physical and chemical properties of bait microalgae and bait effect were researched. The results showed that various biochemical contents of bait microalgae had no significant difference between after flocculation and before. The bait effect was good.(3) By measuring the survival rate and the specific growth rate of microalgae above after cryopreservation, it is explored that the effect of the concentrated method of microalgae, the storage temperature, the microalgae age and antifreeze protectantson cryopreservation of bait microalgae concentrated solution. When there was not any antifreeze protectant, under 4℃ the survival rate and recovery growth of algal cells were better than under-10℃, and -30℃; The cryopreservation effect of algal cells in the early days of the stationary phase was better than in the logarithmic phase. The preservation effect was affected by the kinds and concentrations of antifreeze protectants.(4) By measuring the intracellular protein, polysaccharide, chlorophyll and total lipid contents and observing morphology, spontaneous fluorescence of algal cell after bait microalgae above were preserved for three months under 4℃,-10℃ and -30℃, which researched the effect of cryopreservation on the algal cells in bait microalgae concentrated solution. The results showed that besides total lipid content was not affected, the rest of the nutrient contents had been significantly affected by the preserved temperature.The vast majority of algal cells in the process of cryopreservation could maintain the morphological integrity, but the spontaneous fluorescence intensity of intracellular chlorophyll could be affected by low temperatures.