Pyrethroid bioaccumulation in field-collected insecticide-resistant Hyalella azteca

Area of Science:

• Environmental Toxicology
• Aquatic Ecology
• Chemical Risk Assessment

Background:

• Wild-type Hyalella azteca are highly sensitive to pyrethroid insecticides.
• Insecticide-resistant H. azteca can bioaccumulate pyrethroids, creating a risk for trophic transfer in aquatic systems.

Purpose of the Study:

• To investigate pyrethroid bioaccumulation in insecticide-resistant Hyalella azteca populations.
• To assess the potential for trophic transfer of pyrethroids in aquatic food webs.

Main Methods:

• Collected four populations of pyrethroid-resistant H. azteca and sediment samples seasonally.
• Measured concentrations of nine current-use pyrethroids in H. azteca tissues and sediment.
• Calculated biota-sediment accumulation factors (BSAF) for key pyrethroids.

Main Results:

• Bifenthrin was detected in all H. azteca samples (up to 813 ng/g lipid); cyhalothrin and permethrin were less frequent.
• Sediment pyrethroid concentrations exceeded toxic thresholds for non-resistant organisms.
• Bifenthrin concentrations in H. azteca were higher in winter, suggesting seasonal influences on bioaccumulation.
• BSAF values for bifenthrin and permethrin in resistant H. azteca were comparable to less sensitive invertebrates.

Conclusions:

• Pyrethroid resistance in H. azteca facilitates bioaccumulation and presents a potential pathway for trophic transfer to higher aquatic species.
• Seasonal factors may influence the extent of pyrethroid bioaccumulation in H. azteca.
• The findings highlight the ecological risk posed by pyrethroid-resistant invertebrates in contaminated aquatic environments.