Arctic food affects mercury in polar bears

ANN ARBOR, Mich., Dec. 9 (UPI) -- U.S. and New Zealand-led researchers say environmental threats such as mercury pollution, as well as global warming, are threatening polar bears' existence.

New research led by biogeochemists Joel Blum of the University of Michigan and Travis Horton of the University of Canterbury, located in Christchurch, New Zealand, focused on assessing the effects of mercury deposition and climate change on polar bears.

Approximately 150 tons of Mercury, a naturally occurring element, enters the Earth's environment each year from human-generated sources, the scientists said. That mercury, deposited on land or into water, is picked up by micro-organisms that convert some of it to methylmercury -- a highly toxic form that builds up in fish and the animals that eat them.

As bigger animals eat smaller ones, the methylmercury is concentrated -- a process known as bioaccumulation. Sitting at the top of the food chain, polar bears amass high concentrations of the contaminant.

The study by Horton, Blum and colleagues showed polar bears get most of their nutrition from phytoplankton-based food webs and, therefore, have greater mercury concentrations than animals participating primarily in ice algae-based food webs.

"This work provides background information that will be important in our in-depth understanding of mercury bioaccumulation in polar bears," said Blum

The study that included Zhouqing Xie, Michael Hren and C. Page Chamberlain appears in the journal Polar Research.