The role of Dileptus anser on the detritus chain was studied in batch culture experiments carried out in three 500-ml Erlenmeyer flasks. Culture solutions of bacteria and Tetrahymena pyriformis were suspended in 500-ml Erlenmeyer flasks containing 100 ml of sterilized CE medium. 0, 1 and 8 cells ml-1 of D. anser were added to each flask on day 0. Three series of experiments were performedusing the control system (No.1) and the systems with D. anser added (No.2, No.3). The batch experiments were carried out over a 7-day period at 20°C. Eight ml of the culture solution was collected from each flask on day 0, 3 and 7. The amount of bacteria was assessed by the plate culture method and direct method, and protozoan species were examined. The concentration of DOC and that of ATP containing one cell of bacteria were measured.
It was shown that the presence of D. anser led to a decrease in density of bacteria when therewas not enough T pyriformis as prey for D. anser. The clearance rate of DOC in each system on day 7 was 14, 26 and 49% respectively. The concentration of ATP contained in one cell of bacteria of each system on day 3 was 5.3×10-13, 6.1×10-13 and 8.2×10-13mg-ATP·mg-cell-1 respectively. It was found thata high concentration of ATP contained in one cell of bacteria led to a high rate of degradation of DOC. The study confirmed that D. anser greatly influences the population of other microorganisms, and the concentration of ATP contained in one cell of bacteria could enhance the degradation of dissolved organic carbon.
