[Variation of bacteria numbers in fish-shrimp mix-culturing ecosystem]

The study on variation of bacteria numbers in Penaeus chinensis-fish mix-culturing ecosystem in 1997. Indicated that at the beginning of culturing season, total number of heterotrophic bacteria and that of nitrate-reducing bacteria in mix-culturing ponds was low, but it was higher than that in mono-culturing shrimp pond. With time going on, the number of bacteria in mono-culturing pond increased rapidly and remained at a high level in August and September, an that in mix-culturing ponds also increased. But the latter increased slowly, and it was never over 10(4) cells.ml-1 and dropped in September. Number of bacteria in bottom of the ponds varied with the similar regulation, but the numbers was 10-100 times higher. The numbers of vibrio in mix-culturing ponds was always lower than that in contrastive pond at the same time. So, in fish-shrimp mix-culturing ponds, the contents of organic matter were lower and the total amount and variability of phytoplankton were higher than corresponding items in mono-culturing pond. It was concluded that mix-culture could stimulate and control the growth of heterotrophic bacteria, accelerate the degradation of organic pollutants, consequently fasten and stabilize the circulation of mater in ecosystem of ponds in culturing season.