Effects of trace metals on larvae and adults of the buff-tailed bumble bee

The accumulation of trace metals and metalloids (TMM) in organisms is known to cause severe cellular and physiological damage. Increasing concentrations of TMM in nesting materials and floral resources have been identified as potential threats to bee populations. Despite this concern, the effects of TMM on bees, particularly during their larval and adult stages, remain poorly understood. In this study, we examined the impact of field-realistic concentrations of copper and cadmium, as determined by the PoshBee project, on the buff-tailed bumble bee (Bombus terrestris). First, we assessed the ability of bumble bees to detect these metals. Our findings revealed that bumble bees could not detect TMM in sucrose solutions, except for copper at a high, field-unrealistic concentration (LC50). Second, behavioural assays showed no significant effects of TMM exposure on walking and flying behaviours, oocyte size, or lipid content in adult bumble bees, indicating a lack of sublethal effects at these concentrations. Third, larvae fed with copper-laced food exhibited accelerated pupation, although no other developmental impacts were observed. While these results may seem reassuring for bumble bee populations regarding TMM pollution, they may be overly optimistic. We recommend future research to employ field-realistic concentrations from TMM-polluted areas (e.g., near industries) to better understand the potential risks for bee health and development.