Laboratory experiments on the effect of prometryn on the growth process of crucian carp(Carassius auratus) and the variation of nutrient concentrations
In order to evaluate the ecological risk of prometryn in the water environment, prometryn and crucian carp (Carassius auratus) were chosen respectively as the target pollutant and target organism to investigate the effect of prometryn on the growth of crucian carp and the variations of nutrient concentrations in the water. To this end, the weight and length of crucian carp raised in the aquariums in the laboratory and the concentrations of nutrients in the water were continuously monitored. The results showed that variations of fish weight gain rates, length gain rates, and nutrient concentrations with time could be described well with Logistic equation (R2=0.959-0.997), and the weight gain rate and protein efficiency ratio of fish in groups with prometryn was 8.7%-50.3% (P<0.05) lower than those in groups without prometryn. In fishless groups, no significant effect of prometryn on nutrient concentrations and ratios of TN/TP concentration was observed; whereas when there was fish in the aquariums, TPN and TPP concentrations with prometryn were 41.4% and 33.8% (P<0.05) lower than those without prometryn respectively. In addition, prometryn also had a significant effect on the proportion of various nutrients and total TN concentration/total TP concentration (P<0.05). It was shown that the toxic effect of prometryn on crucian carp could indirectly affect the concentrations of nutrients in the water.