Transgenerational effects of water-soluble polymers on Daphnia magna at environmentally relevant concentrations: The role of multigenerational plasticity.

The widespread use of water-soluble polymers (WSPs) like polyethylene glycol (PEG) and polyvinyl alcohol (PVA) across multiple industrial and household uses has recently raised concerns about their environmental persistence and potential toxicity to aquatic organisms. Despite being excluded from regulatory oversight, recent studies suggest possible ecological risks associated with sub-lethal exposures to these polymers. In this context, this study investigates the transgenerational effects of PEG and PVA on Daphnia magna, focusing on both life-history parameters and epigenetic modifications at the environmentally relevant concentration of 1 μg/L. Through continuous exposure experiments, spanning three generations (from F0 to F3), and "recovery" groups, where only the parental generation (F0) was exposed, our results reveal significant reductions in the number of newborns and reproductive parameters in the F0 generation exposed to PEG but not in subsequent generations. This suggests a multigenerational plasticity in Daphnia through a compensatory or acclimation reproductive response over time. Global cytosine methylation patterns also showed a significant initial increase in the F0 generation exposed to PEG, which decreased in later generations, indicating a possible epigenetic mechanism underlying observed reproductive effects. In contrast, PVA exhibited no significant changes in both life history parameters and methylation but showed a global methylation trend suggesting its likely epigenetic influence. These findings underscore the need for comprehensive risk assessments of WSPs, particularly their potential for inducing long-term (epigenetic) effects, influencing reproductive functions across generations and how increased plasticity may affect responses against novel other stressors.