Acute toxicity of some treatments commonly used by the salmonid aquaculture industry to Corophium volutator and Hediste diversicolor: Whole sediment bioassay tests

The commercial farming of Atlantic salmon, Salmo salar, typically requires the periodic application of copper-based anti-foulants and chemotherapeutic treatments, including Slice®, Excis®, Salmosan® and Aquatet®/Tetraplex® to reduce the effects of biological pests. Information on the environmental safety of any chemical agent released into the aquatic environment must be obtained before a product can be licensed for use, but such information typically exists only in confidential technical reports which can be difficult to obtain. Furthermore, different test organisms, experimental protocols and reporting procedures make comparison of the various compounds/studies difficult. Here we present a series of 10-day, whole sediment bioassay tests that determined the concentrations of emamectin benzoate (EB), cypermethrin (CP), azamethiphos (AZ) and oxytetracycline hydrochloride (OTC), the active ingredients of the aforementioned chemotherapeutants, and copper, that caused 50% mortality (LC50) in the non-target benthic crustacean, Corophium volutator. Additional whole sediment bioassays of identical design were conducted with the non-target polychaete worm, Hediste diversicolor exposed to copper and EB. C. volutator demonstrated similar sensitivity to EB and AZ, with LC50s of 153 (95% confidence intervals, CI = 119–198) and 182 (95% CI = 152–217) µg active ingredient [kg wet sediment]− 1 respectively. OTC caused 50% mortality of C. volutator at a concentration of 414 (95% CI = 233–734) µg OTC [kg wet sediment]− 1. The LC50 for H. diversicolor exposed to EB was 1368 (95% CI = 744–2516) µg EB [kg wet sediment]− 1, an order of magnitude greater than that for C. volutator. Conversely, C. volutator was able to tolerate much higher concentrations of copper than H. diversicolor, with LC50s of 193,326 (95% CI = 171,034–218,523) and 74,988 (95% CI = 61,192–91,895) µg Cu [kg wet sediment]− 1 respectively. CP was the most toxic to C. volutator of all compounds investigated, causing 50% mortality at a concentration of 5 (95% CI = 4–6) µg CP [kg wet sediment]− 1. These data allow direct inter-comparison of the toxicities of some of the commonly applied treatments used by the global salmonid aquaculture industry.