Influences of a Laboratory Diet and Natural Seston on the Bioavailability of Carbaryl, Chlorpyrifos, and Malathion to Black Fly Larvae (Diptera: Simuliidae) in an Acute Toxicity Test

摘要

To determine the effects organic food particles can have on insecticide bioavailability, two food types, a laboratory diet and dried, natural seston, were evaluated using black fly larvae, Simulium vittatum Zetterstedt cytospecies IS-7, in a 24-h orbital shaker toxicity test. The bioavailability of all three insecticides was significantly altered when diet concentrations in the flasks were ≥150 mg/L. Chlorpyrifos availability decreased, whereas carbaryl and malathion availability increased. Dried, natural seston had little effect on the bioavailability of these insecticides except in carbaryl-dosed larvae where mortality was significantly increased when seston concentrations were 150 mg/L in the flasks. Differences in insecticide bioavailability between the two food types in these experiments might have been related to the particle size and organic carbon content of the two materials. Laboratory diet particles were significantly smaller (11.7 ± 0.5 μm) and had a significantly greater organic carbon content (26.4%) than the seston particles (30.9 ± 3.3 μm; 1.1%). These results suggest that the concentration, as well as the physical and chemical component of the food source, are important factors in determining the effects of food on insecticide bioavailability in aquatic systems.