Acute toxicity and antioxidant enzyme responses of Gammarus sp. exposed to malathion in Caspian Coastal Waters

Articles in Press

Document Type : Research Paper

Authors

1 Department of Biology, Faculty of Science, University of Guilan, Rasht, Iran

2 Department of Marine Biology, Islamic Azad University, Lahijan Branch, Lahijan

3 Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran

10.22124/cjes.2026.9877

Abstract

Malathion is a widely used organophosphate insecticide in Northern Iran, where agricultural runoff may introduce it into the Caspian coastal ecosystems and threaten non-target aquatic invertebrates. This study evaluated the acute toxicity of a commercial malathion formulation (57% emulsifiable concentrate) and the sublethal antioxidant responses of the Caspian amphipod Gammarus sp. collected from the western coast of Bandar Anzali, Iran. Under laboratory conditions, acute toxicity was assessed at six nominal malathion concentrations (0.2–2.2 µg L⁻¹). Probit analysis estimated the 96-h median lethal concentration (LC₅₀) at 0.97 µg L⁻¹, from which a maximum allowable concentration of 0.097 µg L⁻¹ was derived. For the sublethal exposure experiment, amphipods were exposed to 0.1, 0.2, 0.3, and 0.5 µg L⁻¹ malathion for up to 96 h. Superoxide dismutase (SOD) and catalase (CAT) activities were measured as biomarkers of oxidative stress. Both enzymes showed significant time- and concentration-dependent changes relative to the control. Superoxide dismutase activity increased progressively and reached its highest level after 72 h of exposure. In contrast, CAT activity showed an early transient increase, peaking between 24 and 48 h depending on malathion concentration, followed by a decline towards control levels at 96 h. The contrasting temporal patterns of SOD and CAT indicate that prolonged exposure to sublethal malathion concentrations may disrupt antioxidant defence in Gammarus sp. These findings indicate the high sensitivity of this amphipod to malathion and support the use of SOD and CAT activities as biomarkers of organophosphate-induced oxidative stress in the Caspian coastal environments.
 

Keywords

Caspian Journal of Environmental Sciences

Articles in Press, Corrected Proof
Available Online from 27 August 2026

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