| Small bodies of water in forested areas are usually not marked or named on maps, they are often difficult to see from the air, and they have little forest canopy cover to screen them from aerial deposition. Therefore, in forest areas receiving aerial application of pesticides, small ponds are at risk of receiving high concentrations of contaminants.; Four acidic bog ponds near Lake George, New Brunswick, were treated experimentally with the insecticide fenitrothion. Formulated fenitrothion was applied from ground level with a mist blower to determine the sensitivity of the bog pond invertebrate community. Insect emergence, gyrinid populations, and the invertebrate community inhabiting the floating sphagnum fringe of the ponds were sampled before and after treatment in 1984 and 1985. Recovery of the invertebrate community in treated ponds was further monitored in 1986.; The bog pond aquatic invertebrate community was found to be sensitive to formulated fenitrothion. Concentrations of fenitrothion in bog pond water were in ranges that would be expected after a direct aerial application, with no buffer zone, at operational emission rates used for spruce budworm, of 210 g active-ingredient ha{dollar}sp{lcub}-1{rcub}{dollar}. Insect emergence was reduced for 6 to 12 weeks following fenitrothion treatment. Two ecologically important and numerically abundant insect families, the Chironomidae and Ceratopogonidae, had their population densities reduced by greater than 50% for one month after treatment. Most other benthic insect taxa present were also reduced in density. Some reductions in density lasted over winter into the next year. Effects lasting over a few weeks, are contrary to the usual small and transitory effects of fenitrothion on aquatic invertebrate communities in streams or large lakes.; Insecticide-induced suppression of aquatic insects and adult insect emergence in the small bog ponds allowed Hydrachnellae, Oligochaeta, and Nematoda to dominate the aquatic invertebrate community. Export of energy and nutrients to the terrestrial system via insect emergence was thus reduced and cycling or retention within the aquatic system increased. Sustained suppression of insect emergence could result in nutrient accumulation in the ponds. Loss of emerging insects as a food resource could have effects on higher predators in the bog ecosystem. |
