The researchers note that their work, performed in the laboratory, needs to be done next in the field because the bees' reduced response to sugar could diminish floral resources needed to support coworker bees and larvae in the field.

In preliminary studies they conducted in the field, the researchers found that some foragers leaving radish plants were carrying pollen with high concentrations of selenium. Further, they noted that plants with high concentrations of selenium were being visited by foragers just as frequently as were plants with no selenium, suggesting that the bees do not avoid feeding on selenium.

"The consequences of their inability to avoid selenium could be substantial," Trumble said. "We must emphasize that our data do not show that large losses of honey bees are currently occurring or that there is any relationship with Colony Collapse Disorder (CCD). Field studies need to be conducted to determine if honey bees collect enough selenium from contaminated plants to cause significant effects on learning, behavior and adult or larval survival."

(For more, see: Piecing together colony collapse disorder clues)

The researchers already have received a three-year 480,000 grant from USDA-NIFA to take their research from the lab to the field. The grant, which will support Hladun's postdoctoral work at UCR, will allow the researchers also to investigate other elements, such as cadmium and lead, which have been found in urban honeybee hives.

"In our lab experiments, we focused on individual bees," said Hladun, who will graduate with a Ph.D. this summer. "But bees are social insects. In our future work, we plan also to focus on whole colony health."

Selenium occurs naturally in certain soils from shale deposits of prehistoric inland seas. Agricultural drainage dissolves selenium from these soils and causes the buildup of selenate. One of the worst cases of selenium pollution is the San Joaquin Valley in California, a major drainage site for many of the state's agricultural regions and an area that has reported honey bee loss due to CCD.