Soil lead contamination decreases bee visit duration at sunflowers

Abstract

Legacies of lead contamination present challenges in the management of urban greenspaces for beneficial insect conservation. In particular, the sublethal effects of lead contamination on bee foraging behavior could negatively impact plant-pollinator interactions and the sustainability of urban agriculture. It is difficult, however, to distinguish between differences in foraging behavior caused by lead contamination directly as compared to differences resulting from variation in floral traits, which can also be affected by contamination. We compared the foraging behavior of bees, specifically the number of visits and visit duration, at sunflowers grown in lead-contaminated and uncontaminated soils. We also measured soil lead contamination’s effects on sunflower morphological traits. While the number of visits a sunflower head received was not affected by soil lead contamination, bee visit duration was shorter at sunflowers grown in lead contaminated soil. This effect of lead contamination on visit duration was not mediated by sunflower floral traits, which were themselves affected by lead contamination. The inability of bees to distinguish between sunflowers grown in contaminated vs. uncontaminated soil prior to visitation suggests a possible bioaccumulation pathway for lead in bees.