Effects of temperature and salinity on bioconcentration and toxicokinetics of permethrin in pyrethroid-resistant Hyalella azteca

Abstract

Recent studies demonstrated pyrethroid resistance associated with voltage-gated sodium channel mutations in populations of the epibenthic amphipod, Hyalella azteca. Resistant populations were able to tolerate and bioconcentrate pyrethroids at concentrations significantly higher than toxic levels for non-resistant populations. In conjunction with elevated bioconcentration potential, environmental alteration particularly as a result of global climate change is anticipated to significantly alter abiotic parameters including temperature and salinity. These changes are expected to influence uptake and biotransformation of contaminants. Thus, the aims of the current study were a) to examine the bioconcentration potential of permethrin in two pyrethroid-resistant clades of H. azteca and b) assess the influence of temperature and salinity changes on toxicokinetic parameters. Two pyrethroid-resistant clades of H. azteca were exposed to 14C-permethrin at three salinities (0.2, 1.0 and 6.0 practical salinity units (PSU)) and temperatures (18, 23 and 28 °C). Tests were conducted for up to 36 h and uptake, elimination and biotransformation rates were calculated. Both populations demonstrated bioconcentration factors (BCFs) between five and seven times greater than published data for non-resistant H. azteca, with significant differences between clades. Calculated BCF values were comparable to field populations of resistant H. azteca, emphasizing the potential for elevated pyrethroid bioconcentration in the natural environment and increased exposure for predators consuming pyrethroid-resistant aquatic invertebrates. Alterations to temperature and salinity had no statistically significant effect on uptake or parent compound half-life in either population, though biotransformation was elevated at higher temperatures in both populations. Salinity had a variable effect between the two populations, with lower BCF values at 1.0 PSU in clade D H. azteca and greater BCFs at 6.0 PSU in clade C H. azteca. This is the first study to demonstrate the potential for future climate scenarios to influence toxicokinetics in pyrethroid-resistant aquatic organisms.