October 4, 2013
Industrial Toxin Selenium May Be Killing Off Honey Bees
redOrbit Staff & Wire Reports - Your Universe Online
Selenium, a chemical element that is both naturally occurring and often found near mining and industrial activities, can delay the development of or even kill honey bees, according to new research in the October issue of Environmental Toxicology and Chemistry.
Researchers from the University of California, Riverside found that the four primary forms of the anthropogenic pollutant - selenate, selenite, methylselenocysteine and selenocystine - can cause mortality and developmental delays in the insects, which are an important agricultural pollinator both domestically and abroad. The authors believe that the bees could become contaminated through the biotransfer of the metal from selenium-accumulating plants.
“Metal pollutants like selenium contaminate soil, water, can be accumulated in plants, and can even be atmospherically deposited on the hive itself,” explained lead author Kristen Hladun a postdoctoral entomologist at the university. “Our study examined the toxic effects of selenium at multiple life stages of the honey bee in order to mimic the chronic exposure this insect may face when foraging in a contaminated area.”
According to the university, selenium contamination is a global issue that originated from naturally contaminated soils as well as sources that are human in origin, including coal-fired power plants, petroleum refineries or factories. Low concentrations of the element can be beneficial to many creatures – in fact, the authors noted that it is a critical component of an antioxidant enzyme. Higher levels of the metal can be toxic to several different types of insects, however.
Honey bees ingest selenium through contaminated pollen and nectar, Hladun and her colleagues discovered. Organic forms of the metal can alter protein conformation, causing developmental issues, while inorganic forms can lead to oxidative stress. Hladun said that additional research is required to determine if selenium can damage the bee’s internal organs, or if the insect is able to somehow detoxify the compounds.
In addition, she explained that honeybees could be more susceptible to the pollutant due to a lack of detoxification enzymes that other insects still possess. Furthermore, the researchers reported that honey bees in the larval stage are at an increased risk of selenium poisoning than other, similarly-aged insect species.
“Mortality within the hive can reduce the number of workers and foragers overall,” Hladun said. “The forager's ability to tolerate high concentrations of selenium may act against the colony as a whole. Honey bees are social animals and their first line of defense against environmental stressors is the foraging bees themselves.”
“High concentrations of Se (selenium) will not kill foragers outright, so they can continue to collect contaminated pollen and nectar, which will be stored and distributed throughout the colony,” she added. “Selenium occurs naturally in many places around the world, but it also is a byproduct of many industrial activities, and finding ways of recovering and recycling it is key to minimizing the damage to the environment.”
The investigators said that beekeepers can help protect their honey-producers by minimizing their exposure to the substance. Hives should be moved away from contaminated areas, and efforts should be made to keep bees from foraging during flowering periods in plants that could be high in selenium. Hladun also advises improved management of weedy plant species known to be Se-accumulators.
“Currently the researchers are conducting experiments feeding honey bee colonies with Se-laden food,” the university said in a statement. “They will monitor the bees for changes in survival and behavior. In addition, they are exploring the effects of other metal pollutants (cadmium, copper, and lead in particular) that have been found in honey bee hives, especially the ones located near urban or industrial areas.”