In order to explore the effects of addition of green alga(Chlorella vulgaris),bacterium(Bacillus subtilis)and mixture of C.vulgaris and B.subtilis on aquatic environment,growth performance and related enzyme activities of largemouth bass(Micropterus salmoides),juvenile largemouth bass with body weight of(11.71±0.90)g was reared in a 1 000 L polyethylene barrel filled with 800 L water added with C.vulgaris(density of 1×109 cells/L at 6.25 mL/L)(alga group),B.subtilis(1×1011 CFU/g at 0.75 mg/L)(bacterium group),both C.vulgaris and B.subtilis(bacte-rium + alga mixture group),and blank(without any bacterium and alga,control group for days).The results showed that there were generally optimised physical and chemical indices in the water environment in the alga group and bac-terium group during the experiment,compared with the blank group,with the relatively small differences in the total nitrogen,total phosphorus and dissolved oxygen contents in each experimental group,while there were considerably varied in the contents of ammonia nitrogen,nitrate nitrogen and nitrite nitrogen,especially in the water environment in the bacterium + alga mixed group,with the minimal ammonia nitrogen,nitrate nitrogen and nitrite nitrogen con-tents in water in most time points(P<0.05).At the end of the experiment,the largemouth bass in all experimental groups had increase in body weight,weight gain rate,and specific growth rate compared with the blank group,with significant differences in only the bacterium + alga mixture group compared with the blank group(P<0.05).The he-patic glutathione(GSH)content,and activities of catalase(CAT),superoxide dismutase(SOD),glutathione perox-idase(GSH-PX)and lysozyme(LZM)in general were shown to be significantly increased(P<0.05),and malondi-aldehyde(MDA)content to be significantly decreased(P<0.05),especially in the bacterium + alga mixture group compared with the blank group.To sum up,it can be seen that addition of either C.vulgaris or B.subtilis to the water environment can improve the water quality,promote the growth and hepatic antioxidant capacity and immunity in largemouth bass,and addition of both the green alga and bacterium at the same time is more effective.
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