Multi-generational exposure to benzoylecgonine induced multi-level effects in Daphnia magna

Benzoylecgonine (BE) is the main cocaine metabolite, and it has been found in aquatic ecosystems worldwide. Although the environmental concentrations can be considered low, several studies have highlighted that exposure to BE can induce different adverse effects on non-target aquatic organisms. Such studies demonstrated that sub-lethal effects can occur after short-term exposure. However, there is a lack of information about the long-term impact of BE, mainly on multiple generations. The present study intended to assess the effects of BE at different levels of the biological organization caused by multi-generational, long-term exposures on the freshwater crustacean Daphnia magna. Newborns were exposed to two environmentally relevant BE concentrations (0.05 and 0.5 µg/L) for 21 days over four generations. At the end of each exposure, changes in energy reserves, in terms of caloric content (i.e., sub-individual level), body growth, swimming behavior, and reproductive success (i.e., individual level) were assessed. Our results pointed out that environmentally relevant BE concentrations caused effects at sub-individual and individual levels, with differential sensitivity over generations. Overall, BE induced a significant alteration of caloric content, leading to a reduction in swimming activity and body growth, but an increase in reproductive success. These findings suggest that D. magna individuals can differently allocate energy in response to BE exposure, confirming the necessity of further investigations to understand the carry-over effects over different generations and potential consequences on population dynamics.