Research Product

The effects of fenthion on macrobenthic animals that colonized sand-filled boxes at two salt marsh sites were determined after two field sprayings within 5 days and in the laboratory after intermittent exposures that simulated field conditions. ULV ground applications for adult mosquito control resulted in water concentrations <=0.68 µg fenthion/l at one site and <=0.38 µg/l at the other site. There were no statistically significant differences (a= 0.05) in average numbers of benthic individuals and species (primarily annelids and arthropods) that colonized control communities and those exposed to these concentrations. The average numbers of individuals and species of animals that colonized sand-filled boxes in the laboratory (during 9 wk by planktonic larvae from continuously supplied unfiltered seawater) were not significantly affected by two treatments at 1.1 µg fenthion/l or by four treatments at 1.3 µg/l. However, the average number of species in communities exposed to two treatments at 11.8 µg/l was significantly less than that in control communities and those exposed to lower concentrations. Mean abundances of mollusks, arthropods, and chordates were substantially (19 or more percent), but not statistically significantly, lower in this concentration than in the control.