Rising CO2 levels reduce protein in crucial pollen source for bees

http://www.eurekalert.org/pub_releases/2016-04/pu-rcl041316.php

Public Release: 13-Apr-2016
Rising CO2 levels reduce protein in crucial pollen source for bees
Purdue University

Rising levels of atmospheric carbon dioxide have reduced protein in goldenrod pollen, a key late-season food source for North American bees, a Purdue University study shows.

Researchers found that the overall protein concentration of goldenrod pollen fell about one-third from the onset of the Industrial Revolution to the beginning of the 21st century.

Previous studies have shown that increases in carbon dioxide can lower the nutritional value of plants such as wheat and rice - staple crops for much of the global human population - but this study is the first to examine the effects of rising CO2 on the diet of bees.

"Bee food is less nutritious than it used to be," said Jeffrey Dukes, study co-author and professor of forestry and natural resources and biological sciences. "Our findings also suggest that the quality of pollen will continue to decline into the future. That's not great news for bees."

Native bee species and honeybees rely on flowering plants for energy and nutrition. While nectar is the primary energy source for bee colonies, pollen is the sole source of protein for bees. Pollen is essential for the development of bee larvae and helps maintain bees' immunity to pathogens and parasites.

Goldenrod, a common North American perennial that blooms from late July through October, offers bees some of the last available pollen before winter. Bees that overwinter must store substantial amounts of pollen to rear their winter young. Declines in pollen protein could potentially threaten bee health and survival and weaken bees' ability to overwinter on a continental scale, said Jeffery Pettis, study co-author and research entomologist with the U.S. Department of Agriculture's Agricultural Research Service.

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