Impact of lambda-cyhalothrin on a macroinvertebrate assemblage in outdoor experimental channels: implications for...

Area of Science:

• Environmental Toxicology
• Ecotoxicology
• Stream Ecology

Background:

• Pyrethroid insecticides, like lambda-cyhalothrin, are widely used and can enter aquatic environments.
• Understanding their impact on non-target stream organisms and ecosystem processes is crucial for environmental risk assessment.

Purpose of the Study:

• To investigate the effects of a single pulse exposure to lambda-cyhalothrin on a stream macroinvertebrate assemblage.
• To assess the subsequent impacts on microalgal biomass and leaf litter decomposition in experimental stream channels.

Main Methods:

• Macroinvertebrates (Gammarus pulex, Leuctra nigra, Heptagenia sulphurea, Ancylus fluviatilis) were exposed to lambda-cyhalothrin (10.65 or 106.5 ng L(-1)) in laboratory conditions.
• Exposed organisms were introduced into outdoor experimental stream channels with natural substratum for 10 days.
• Drift, macroinvertebrate behavior, microalgal biomass, and leaf litter decomposition were monitored.

Main Results:

• Increased lambda-cyhalothrin concentrations significantly elevated the drift of Gammarus pulex and Leuctra nigra, with reduced mobility observed.
• Microalgal biomass accumulation was significantly higher in channels exposed to the higher lambda-cyhalothrin concentration (106.5 ng L(-1)).
• Leaf litter decomposition rates were significantly greater in control channels compared to those with exposed macroinvertebrates, indicating altered ecosystem functioning.

Conclusions:

• Lambda-cyhalothrin exposure disrupts stream macroinvertebrate behavior and community dynamics.
• The insecticide indirectly affects ecosystem processes, including primary production (algal growth) and decomposition, at environmentally relevant concentrations.
• This research provides valuable insights into the ecotoxicological effects of pyrethroids on stream ecosystem functioning.