Pyrethroid insecticide pollution of wetlands reduces amphipod density

Area of Science:

• Ecotoxicology
• Wetland Ecology
• Agricultural Science

Background:

• Freshwater amphipods are crucial food sources for waterfowl in North American Prairie Pothole Region (PPR) wetlands.
• Declining amphipod populations and their uneven distribution raise concerns, with limited understanding of underlying causes.
• The impact of agrochemicals on PPR wetland ecosystems and amphipod populations remains understudied despite extensive agriculture.

Purpose of the Study:

• To investigate the relationship between amphipod abundance, land use, water quality, and pyrethroid insecticide contamination in wetland sediments.
• To identify potential sources and transport mechanisms of pyrethroids into PPR wetlands.
• To assess the role of landscape features in mitigating pyrethroid exposure.

Main Methods:

• Studied amphipod abundances (Gammarus lacustris, Hyalella azteca) across a gradient of wetland conditions.
• Collected and analyzed wetland sediment for pyrethroid insecticide concentrations.
• Quantified land use, water quality, hydrology, and habitat metrics within study watersheds.

Main Results:

• A significant negative correlation was found between pyrethroid concentrations and amphipod abundance.
• Pyrethroids were detected in 44% of wetlands, particularly in intensively cropped areas with minimal vegetation buffers.
• Pyrethroids occurred even in wildlife reserves, indicating widespread contamination via overland transport and spray drift.

Conclusions:

• Pyrethroid insecticides pose a threat to freshwater amphipod populations in the PPR.
• Intensive agriculture and inadequate vegetative filter strips contribute to pyrethroid contamination of wetlands.
• Forest patches and filter strips can reduce pyrethroid transport and exposure to aquatic ecosystems and their inhabitants.