Field and Laboratory\nEvidence That Chlorpyrifos Exposure\nReduced the Population Density of a Freshwater Snail by Increasing\nJuvenile Mortality

Pesticides have been frequently detected in global freshwater\necosystems,\nbut attempts to document changes in population dynamics of organisms\nupon exposure to pesticides, establish a causal relationship between\nexposure and population effects, and identify the key toxic events\nwithin individuals under natural field conditions remain rare. Here,\nwe used a field survey, a reciprocal cross-transplant experiment,\nand a laboratory toxicity experiment to build a compelling case that\nexposure to the insecticide chlorpyrifos was responsible for differences\nin snail (Bellamya aeruginosa) densities\nin eastern (ELL) and western basins of Liangzi Lake in China. Our\nfield survey and reciprocal cross-transplant experiment revealed significant\ndifferences in snail densities, juvenile percentage, survival, and\nrelative telomere length (RTL) in the two basins. The insecticide\nchlorpyrifos detected in snail tissues was negatively correlated with\nsnail densities, the percentage of juvenile snails, and RTL and had\nan extremely high risk quotient in ELL. In the laboratory experiment,\ntissue concentrations of chlorpyrifos detected in ELL were associated\nwith reduced RTL and increased juvenile mortality in B. aeruginosa. These results support the hypothesis\nthat chlorpyrifos exposure in ELL reduced the density of snails by\nreducing juvenile survival and, consequently, recruitment to the adult\npopulation.