CLAMity: Mixtures of agricultural pesticides as multiple stressors in a bivalve species

Pesticides play a vital role in ensuring global food security amid a growing global population; however, their movement away from application sites can pose significant risks to the health of non-target species. Pollution of freshwater is a key contributor to the high extinction rates of freshwater species, which often face exposure to a complex "cocktail" of pollutants simultaneously. A better understanding of pesticide interactions will enable more targeted policies and land management practices to mitigate environmental damage while ensuring food security. In this study, Corbicula fluminea (Asian clam) were exposed to binary pesticide mixtures commonly found in two rivers in the South of England. The exposures involved individual pesticides and mixtures at a concentration of 0.1μg/L per pesticide. Selected molecular markers were targeted and proved to be impacted by the timing and the pesticide mixture; an Integrated Biomarker Response (V2) value was also calculated. Our results show that both seasonality and the chemicals characteristics of the pesticides may significantly modulate their toxicity, both individually and in a mixture. When put into the context of catchment management this data combined with pesticide monitoring could improve estimating ecological risk. To the authors' knowledge, this is the first study to assess the molecular responses of these mixtures in bivalve molluscs using the IBR_v2 value following exposure to combined pesticides.