Mercury Levels in Polar Bears Determined by Food Web
10.12.2009 - Flora & Fauna, Other, Arctic
New research, conducted by biogeochemists Travis Horton of the University of Canterbury and Joel Blum of the University of Michigan, opens a new perspective in the study of mercury deposition in polar bears.
While mercury occurs in many naturally occurring compounds, it can be turned into a highly toxic form when picked up by microorganisms once deposited on land or in water. As you go up the food chain the levels of mercury increase due to a process called bioaccumulation. Extremely high levels can be found in species at the top of the food chain such as polar bears.
Collecting polar bear hair samples from museum specimens from the 19th and 20th centuries, the scientists looked at three different chemical signatures (nitrogen isotopes, carbon isotopes, and mercury concentrations) in the hairs. The evidence shows that there are two distinct food webs with two distinct bases: one with microscopic plants floating on the surface of the ocean and the other with algae from the sea ice. The study concludes that polar bears feeding on phytoplankton-based food webs have higher mercury concentrations than those that do not, making it possible for scientists to better understand the effects of climate change on polar bears through the distinction it makes between the two food webs.
