Synthetic Pesticide Levels in Antarctic Penguins Present a Complex Mystery
06.05.2008 - Other
For the past 30 years, DDT (Dichloro-Diphenyl-Trichloroethane synthetic pesticide) derivatives have persisted in Antarctic penguins at a constant level, and researchers say glacial meltwater may be the source.
The use of DDT peaked several decades ago at more than 36,000 metric tons per year (t/yr). Today, less than 1000 t of the organochlorine pesticide-banned in most countries since the 1980s-is applied annually for mosquito control and farming, mainly in the Southern Hemisphere. Despite this drop, Adélie penguins in the Antarctic continue to have the same levels of total DDT in their bodies as they did 30 years ago. New research published in ES&T identifies Antarctic meltwater as the continued source of total DDT, and possibly other pollutants, in the southern continent's ecosystems.
DDT and other persistent organic pollutants (POPs) follow atmospheric paths to the Antarctic and the Arctic and eventually are deposited there in snow and ice. Animals at both poles sequester the derivatives DDT in their fat. But while Arctic-dwelling creatures such as birds, whales, and seals have shown a dramatic drop in total DDT levels during the past decade, levels in Adélie penguins in the Antarctic have remained steady, according to the new results.
According to Derek Muir of Environment Canada, the "remarkable" differences between Arctic and Antarctic trends for DDT in seabirds, ringed seals, and other animals present a complex mystery. The Arctic ice holds more DDT because of its past use in the Northern Hemisphere, but declining levels in animals there "suggest it is not having a large impact". The new results "point out the need to examine this in more detail," particularly in the Arctic, where researchers have collected more high-resolution data over time on DDT in animals.
