Effect of UV-B radiation on the population dynamics of the rotifer Brachionus urceus

The effect of UV-B radiation enhancement at experimental doses of 0.00, 0.24, 0.48, 0.72, 0.96, and 1.20 kJ/m² on the population dynamics of the rotifer Brachionus urceus feeding on the alga Chlorella sp. was studied under controlled laboratory conditions using clonal culture and life-table techniques. The results show that UV-B radiation treatment significantly shortened the survival time of the rotifer (P <0.05):The longest survival time (336 h) occurred in the control (0.00 kJ/m²) while the shortest (222 h) occurred when exposed to the highest UV-B radiation treatment (1.20 kJ/m²). The fecundity of the rotifer B. urceus was enhanced by the lower UV-B radiation treatment (0.24 and 0.48 kJ/m²) but inhibited by the higher treatments (0.96 and 1.20 kJ/m²). Life expectancy also was obviously affected by UV-B radiation (P <0.05). The highest life expectancy occurred in the control (0.00 kJ/m²), and it became shorter with increasing doses of UV-B radiation. The resutls in the present study indicate that the life expectancy of the rotifer B. urceus can be used as an indicator for UV-B radiation enhancement.