Assessing the toxicity of chemical compounds associated with marine land-based fish farms: The use of mini-scale microalgal toxicity tests

Many chemicals that are currently used in aquaculture have not been evaluated with regard to their specific effects on the aquatic environment. In the present study, the toxic effects of several chemicals associated with land-based marine fish farming activities were assessed using two species of marine microalgae (Phaeodactylum tricornutum and Isochrysis galbana). Mini-scale toxicity tests were performed with six antibiotics (amoxicillin, ampicillin, flumequine, oxytetracycline, streptomycin and sulfadiazine) and two disinfectants (formaldehyde and hypochlorite). Amoxicillin and streptomycin did not exert toxic effects. Sulfadiazine was the most toxic chemical; the EC₅₀ values were 0.11 mg/L and 1.44 mg/L for P. tricornutum and I. galbana respectively. As expected, the disinfectants displayed high toxicity, and P. tricornutum was particularly sensitive to these compounds. Although the differences in microalgal sensitivity depended on the chemical considered, both species were highly sensitive to most of the compounds tested. We recommend the inclusion of mini-scale microalgal toxicity tests in environmental risk assessment (ERA) and environmental monitoring plans because they are cost-effective and rapid.