Macroinvertebrate community response to pulse exposure with the insecticide lambda-cyhalothrin using in-stream...

Area of Science:

• Environmental Science
• Ecotoxicology
• Freshwater Ecology

Background:

• Pesticide application in agricultural catchments raises concerns about aquatic ecosystem health.
• Limited data exists on the in-situ impact of pesticides on aquatic biota during natural exposure events.

Purpose of the Study:

• To investigate the impact of the pyrethroid lambda-cyhalothrin on natural macroinvertebrate communities in an in-stream mesocosm.
• To assess macroinvertebrate drift and community structure changes following pulse exposure to lambda-cyhalothrin.

Main Methods:

• An in-stream mesocosm setup was used to expose natural macroinvertebrate communities to lambda-cyhalothrin pulses.
• Macroinvertebrate drift was measured using nets before, during, and after exposure.
• Benthic samples were collected quantitatively before and after exposure to assess community structure.

Main Results:

• Macroinvertebrate drift significantly increased immediately after lambda-cyhalothrin exposure across all tested concentrations.
• Taxa such as Gammarus pulex, Ephemeroptera, Leuctra sp., and Simuliidae exhibited pronounced drift responses.
• Significant structural changes in the macroinvertebrate community were observed only at the highest concentrations (5.00 and 10.0 microg L(-1)).

Conclusions:

• Pulse exposure to lambda-cyhalothrin causes immediate and significant macroinvertebrate drift in freshwater ecosystems.
• Aquatic communities demonstrated a recovery period of approximately two weeks following pesticide exposure.
• Findings contribute to evaluating pyrethroid impacts in natural environments and refining laboratory-based risk assessments.