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Adélie penguin in Antarctica feeding two newly hatched chicks. Photo credit: Hugh Ducklow

DDT Found in Penguins Due to Melting Glaciers

The pesticide DDT was banned in much of the world in the 1970’s, but Adélie penguins today carry the same DDT levels in their bodies as the species did 30 years ago, when DDT was heavily used world-wide for insect control. Research conducted by Ecosystems Center scientist Hugh Ducklow and his student Heidi Geisz of the Virginia Institute of Marine Science (VIMS) shows  that Antarctic meltwater is the source of the pesticide.

DDT and other persistent organic pollutants reach the polar regions through the atmosphere. While the level of DDT in Arctic birds, whales and seals has dropped dramatically, the DDT level in Adélie penguins has stayed the same.

For their study, published last month in the journal, Environmental Science and Technology, Ms. Geisz, Dr. Ducklow and VIMS scientist Rebecca Dickhut sampled dead Adelie penguins and compared the results with measurements from decades ago. They discovered that the birds have been exposed to remnants of old DDT, not new sources. DDT is still used, in much smaller quantities, in the Southern Hemisphere.

The scientists found that there is very little recent DDT deposition in Antarctica, but have discovered measurable amounts in the meltwater that comes from the Antarctic Peninsula ice sheet, where the DDT is stored from decades ago. Dr. Ducklow and Ms. Geisz estimate that meltwater could be contributing about 1 to 4 kilograms of DDT per year to offshore Antarctic ecosystems.

In addition, they note that climate warming, which, in that area has accounted for a 6º C increase in temperature in the last 30 years, has led to increased volume and frequency of glacial retreat and meltwater.

Geisz, H. N., R. M. Dickhut, M. A. Cochran, W. R. Fraser and H. W. Ducklow. 2008. Melting Glaciers: A probable source of DDT to the Antarctic marine ecosystem. Environmental Science and Technology 42(11): 3958-3962.