Ecotoxicological assessment of arsenic contamination: Biological responses and bioaccumulation capacity in Leptodictyum riparium and Lymnaea stagnalis, individually and in a microcosm

Arsenic (As) is a widespread environmental pollutant recognised by the World Health Organization (WHO) and the International Agency for Research on Cancer (IARC) as posing a serious threat to human health due to its toxic, teratogenic and carcinogenic properties. As is highly mobile and persistent in aquatic environments, where it can bioaccumulate in organisms and enter the food chain. Although regulatory agencies have set the maximum limit for As in drinking water at 10 μg/L, concentrations often exceed this threshold, exposing millions of people worldwide to significant health risks. Phytoremediation has emerged as a promising, cost-effective strategy for mitigating metal contamination, particularly using hyperaccumulating plant species. In this study, we investigated the phytoremediation potential of the aquatic moss Leptodictyum riparium, examining its capacity to reduce the bioavailability and toxicity of As individually and in a freshwater microcosm. We also evaluated whether the presence of the moss could mitigate As bioaccumulation and related toxic effects in the freshwater gastropod Lymnaea stagnalis, a well-established biomonitor of aquatic contamination. To this aim, As bioaccumulation and bioaccumulation factor; the levels of reactive oxygen species (ROS); the antioxidant enzyme activities, and the expression of proteins related to cell death and stress were evaluated. Our results show that L. riparium removed efficiently As from the water, without, however, mitigating As effects in L. stagnalis. Moreover, our results showed that the co-presence of moss and snails impaired the accumulation capacity of both by inducing oxidative stress reactions, through mechanisms that have yet to be elucidated.