枯草芽孢杆菌培育生物絮团对池塘水体浮游生物的影响

为探究枯草芽孢杆菌(Bacillus subtilis)培育生物絮团对浮游生物的影响,以枯草芽孢杆菌作为试验菌种,以养殖池塘水为试验用水,在有机玻璃水族箱(100 cm×60 cm×50 cm)中进行为期40 d的生物絮团培育试验。试验以添加葡萄糖为处理组I,同时添加枯草芽孢杆菌和葡萄糖为处理II组,仅添加枯草芽孢杆菌为处理III组,对照组不添加任何物质。试验过程中每5 d对各组水体取样,对形成的絮团物质进行显微观察,同时对各组水体中浮游生物进行定性和定量分析。结果表明,本试验条件下,处理I组和处理II组在第15天左右形成成熟生物絮团,生物絮团形成前期(试验开始至第15天),生物絮团组(处理I组和处理II组)水体中浮游植物丰度显著高于处理III组和对照组,而絮团形成后期(第15~40天),生物絮团组水体中蓝藻门的微囊藻属(Microcystis)、鞘丝藻属(Lyngbya)和绿藻门的扁藻属(Platymonas)、盘藻属(Gonium)和团藻属(Volvax)的丰度显著低于处理III组和对照组,表明生物絮团的形成前期对浮游植物有明显促作用,生物絮团形成后期对蓝藻门中的微囊藻属、鞘丝藻属和绿藻门的扁藻属、盘藻属和团藻属有明显抑制效果;生物絮团形成后期,生物絮团组水体中轮虫、枝角类和桡足类浮游动物丰度显著高于处理对照III组和对照组,表明生物絮团对轮虫、枝角类和桡足类有明显促进作用。

Effect of a Bacillus subtilis Biofloc on Plankton in Pond Water

Biofloc is an advanced technology in aquaculture and can effectively reduce excessive nitrogen in water, improve the immunity of aquatic animals and provide natural food for some fish species and shrimp. In this study, a biological flocculation test was conducted to evaluate the effects of biofloc on the species number and quantity of plankton in pond water, aiming to provide a reference for treatment of pond culture wastewater and to extend existing research on biofloc technology. From May to August, 2015, a biological flocculation test was carried out in an aquarium (100 cm×60 cm×50 cm) with 250 L of pond water, using glucose as the carbon source and Bacillus subtilis as the experimental strain. Four groups were set for the experiment: a control group; Treatment I, supplemented with glucose; Treatment II, supplemented with both glucose and Bacillus subtilis; Treatment III, supplemented with Bacillus subtilis. The quantity of glucose added in Treatments I and II resulted in a carbon-nitrogen ratio of 20:1 and Bacillus subtilis was added to give 109 CFU/L in Treatments II and III. During the 40 day test, plankton and biofloc were monitored at five day intervals. Biofloc formation was enhanced by the addition of glucose to culture water. The addition of glucose and Bacillus subtilis shortened the formation time of a mature biofloc by about five days, compared to addition of glucose alone. In Treatments I and II, the formation of a mature biofloc both peaked on day 15. Early in the test, phytoplankton abundance in Treatments I and II was significantly higher than in Treatment III and the control, but later the abundance of Microcystis, Lyngbya and Platymonas, Gonium and Volvax in Treatments I and II was significantly lower than those in Treatment III and control. These results indicate that the formation of a biofloc initially increases phytoplankton abundance and then later inhibits the growth of Microcystis, Lyngbya and Platymonas, Gonium and Volvax. The abundance of rotifers, cladocera and copepods in Treatments I and II was also significantly higher than in Treatment III and control late in the experimental period, suggesting that the biofloc promotes the growth of rotifers, cladocera and copepods.