Beneficial Insects and Soil Contamination

Does heavy metal contamination impact bee behavior?

Farming in urban environments is growing rapidly, with market gardens, community supported agricultural operations and small-scale direct farms improving the profitability of farmers, the food security of low-income communities, and the environmental quality of cities nationwide. While the economic, social, and nutritional benefits of urban agriculture highlight its promise, urban farmers are often faced with the challenge of heavy metal contamination of their soils from decades of pollution. While the health risks of heavy metal soil contamination to humans are well established, heavy metals’ impact on beneficial insects is largely unknown. Sunflowers (Helianthus annuus), a popular plant in urban agroecosystems and an important nectar source for pollinators, are hyperaccumulators of lead. This bioaccumulation may result in an exposure pathway for bees.


(photo: Frances recording pollinator visits to a sunflower.)

How is this research conducted?

To evaluate the impact of heavy metal contamination on bee behavior, we grew sunflowers in the greenhouse in soils with varying levels of lead contamination. Our lead treatment levels reflect the variation in regulatory limits for soil lead guidelines: 400 ppm (US Environmental Protection Agency), 80 ppm (CA Office of Environmental Health Hazard Assessment), and an uncontaminated control. On each of three days, we placed mature sunflowers in the field as a randomized complete block design and used security camera systems to monitor insect activity, identify pollinators, and quantify their behavior for an average of five hours each day.

What impact can this research have?

We found that lead contamination negatively affected plant growth and floral traits. There was a significant interaction between soil treatment and flower head area, suggesting that while bumblebees (Bombus spp.) and honey bees (Apis mellifera) spent less time probing flowers grown in lead contaminated soils, this effect was in part mediated by sunflower condition. Our results shed light on a potential mechanism by which heavy metal contamination affects pollination, the sustainability of which is critical to the success of urban agriculture.

This project is lead by Frances S. Sivakoff. Frances is a Postdoctoral Researcher in the Department of Entomology at the Ohio State University.

This material is based upon work supported by the National Science Foundation under Grant No. 1253197.

Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.