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Is Diesel Exhaust Responsible for Honey Bee Disappearance




Diesel pollution snuffs out floral odors, interfering with honeybees' ability to find and pollinate flowers, new research suggests.

Honeybees use both visual and olfactory cues to recognize flowers that produce nectar in return for insect pollination. Not all flowers produce nectar, and bees avoid those that don't by learning to recognize the odors of nectar-bearing flowers.

But these floral odors— which consist of reactive chemicals called volatiles — react with other substances in the atmosphere; in the presence of certain pollutants, these scents can chemically transform into undetectable forms.

The research, led by Dr. Tracey Newman and Professor Guy Poppy at the University of Southampton, claims that exposure to common air pollutants present in diesel exhaust can hinder the honeybees' ability to identify floral odors. This hampers their foraging efficiency as the bees depend on their sense of smell to locate, identify and recognize flowers.

Diesel exhaust that is known for its characteristic smell, contains fine toxic air contaminants. In the previous decade, it was believed that diesel exhaust made up a quarter of the air pollution. The exhaust gases have the capacity to alter the profile of a flora odor.

Scientists produced a synthetic floral odor from a blend of eight volatiles that closely matched those found in oilseed rape flowers. They released the smell into a series of glass containers, and exposed some but not all of the containers to different concentrations of nitrogen oxide gases, leaving others uncontaminated.

Over the course of two hours, the researchers measured the concentrations of the eight volatile compounds under the various conditions.

Within a minute, two volatiles that together accounted for more than 70 percent of the floral odor became completely undetectable within contaminated chambers, but remained detectable in uncontaminated chambers, the team reports.
"A bee has far poorer recognition of an altered floral mix," said study co-author Tracey Newman. "The bee needs to learn the unadulterated version, and if the bee has learned it, it will then struggle with the version that has been chemically altered."

Though the researchers focused on the effects of nitrogen oxide gases on floral odors, other highly reactive contaminants, such as naturally occurring ozone gas, which is toxic only when present close to the ground, may have a similar effect on floral volatiles, the researchers said.

Global honeybee populations have dramatically declined within the past decade or so due to a condition called colony collapse disorder, which has been associated with the spread of synthetic pesticide use and other manmade materials, but remains poorly understood.

The researchers suspect that diesel pollution may be yet another factor playing into colony collapse disorder, and that these new findings should provide further impetus to reduce diesel emissions


Is Diesel Exhaust Responsible for Honey Bee Disappearance Reviewed by Blogs on 3:34 PM Rating: 5

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