Relationship between biochemical biomarkers and pre‐copulatory behaviour and mortality in Gammarus pulex following pulse‐exposure to lambda‐cyhalothrin

The impact of the pyrethroid lambda‐cyhalothrin was studied in an in‐stream mesocosm placed in a natural riffle of a Danish stream. Twice during summer 2002, the natural macroinvertebrate community was exposed in situ to a 30‐min pulse of lambda‐cyhalothrin. During exposure, nets caught macroinvertebrates in drift. Exposed and unexposed individuals of the amphipod Gammarus pulex (L) were transferred to aquaria in the laboratory and monitored for biochemical changes (ie biomarkers), pre‐copulatory behaviour and mortality. Biochemical biomarkers were identified by screening extracts of exposed and unexposed G pulex using high‐performance planar chromatography (HPPC). Biochemical biomarkers were detected 3 h after pulse‐exposure, and one biomarker was persistent up to 7 days after exposure. Pre‐copulatory behaviour (ie pair formation) was significantly impaired up to 5 days after exposure, and had not fully recovered at the end of the observation period. EC 10 (0.5 h) and EC 50 (0.5 h) values for pre‐copulatory behaviour were 0.04 and 0.20 µg litre −1 , respectively. Mortality was significant at 0.35 µg litre −1 with an LC 50 (0.5 h) of 5.69 µg litre −1 . There was a significant relationship between two biomarkers and mortality. The study demonstrated that pulse‐exposure at expected environmental concentrations can reduce local populations of G pulex , resulting in severe impact on populations with limited possibilities of re‐colonisation. Copyright © 2005 Society of Chemical Industry