Study on the influences of probiotics on ecological characteristics of plankton in the maricultural ponds

The influences of probiotics on ecological characteristics of plankton in the shrimp growing ponds were studied. The zooplankton and phytoplankton in the shrimp culture system had been investigated for three months. The results showed phytoplankton density was low in early period with the dominant species of diatom, and increased rapidly from middle stage, and reached the peak with quantities of 70×10⁶~160×10⁶cell · L^-1 and phytoplankton population mainly composed of chlorophyta, while density of zooplankton increased steadily and maintained the highest level of 25×10³~30×10³ ind · m^-3 in the later stage. The main species were euryhalinous and coastal species, and the dominant species were very evident. In the control pond, the density of phytoplankton and zooplankton was lower in the early stage than that in the later stage and was less stable than that in the experiment pond in the later stage, the density of Cyanobacteria of pernicious algae which is harmful to shrimp culture was higher than in the experiment pond in the later stage. The results indicated that Bacillus could inhibit the reproduction of Cyanobacteria and promote the growth of beneficial algae. The plankton diversity index of shrimp pond was lower than that of nature waters, and species evenness was similar to that of natural waters.