Thousands of pharmaceutically active compounds and their metabolites are present in aquatic environments worldwide at concentrations from ng to μgL-1. These low detected amounts show an impact on non-target organisms as they are designed to act at very low concentrations. However, pollutants persist in aquatic environments as complex mixtures. But how can these mixtures affect aquatic organisms? It remains largely unresolved.

The aim of the study was to determine how differs the response to the exposure of a combination of six pharmaceuticals (citalopram, sertraline, oxazepam, venlafaxine, tramadol, methamphetamine) from their individual exposure effects and how it affects the exploratory and sheltering behaviour as well as life history traits of crayfish. In the absence of shelter, exposed crayfish moved significantly shorter distances and at a lower velocity and showed significantly less activity than that of the control. With available shelter, exposed crayfish moved significantly longer distances, showed higher activity, and spent significantly more time outside the shelter than that of the control. Results suggest that environmentally relevant concentration of the mixture used can alter the behaviour of non-target aquatic organisms even more than detected in an individual exposure to these compounds. It may lead to deterioration of crayfish populations health, their higher vulnerability to predation and consequently into disruption of ecosystem processes. However, there is a need of more studies focused on different combinations of pollutants and their mode of action in the aquatic environment.

Further detailed information can be found in the original article: Hossain, M.S., Kubec, J., Guo, W., Roje, S., Ložek, F., Grabicová, K., Randák, T., Kouba, A., Buřič, M., 2021. A combination of six psychoactive pharmaceuticals at environmental concentrations alter the locomotory behaviour of clonal marbled crayfish. Science of the Total Environment 751: 141383.

Activity, velocity, time spend outside the shelter and distance moved by marbled crayfish Procambarus virginalis, exposed to a cocktail of pollutants (sertraline, oxazepam, citalopram, venlafaxine, tramadol, methamphetamine) compared to the control in conditions without (A) and with (B) available shelter.