The crumble of 10,000-year-old glacier ice into the sea rumbles thunder through a crisp and cloudless Antarctic summer day. Polar amplification of climate change has our ancient glaciers melting faster every year. However, it is the pesticide chemicals released into penguin foraging areas by this melting ice that interests Heidi Geisz.
Geisz, a VIMS Ph.D. student with professors Rebecca Dickhut and Hugh Ducklow, has found that DDT and its breakdown products persist within the tissues of Adélie penguins, three decades after use of the powerful pesticide was banned in most countries. Like their emperor penguin cousins, Adélies don’t migrate out of Antarctica, so Geisz knew the pollutant source was local.
DDT and other persistent organic pollutants, or POPs such insecticides, industrial wastes and flame-retardants accumulate in the Antarctic and Arctic via transport in the atmosphere. Deposited on the sea ice, these chemicals enter the short Southern Ocean food web, where penguins are top predators.
“It was a mystery,” says Geisz, “We did not see a decline of DDT in the penguin tissues, yet we had not seen any DDT in Antarctic air, snow, ice or ocean water.” However, DDT was found in glacial meltwater. We now know accelerated melting due to global warming implicates a new source of old DDT to Antarctica’s coastal waters.
Ducklow leads a National Science Foundation funded team of researchers examining the ecosystem level effects of global climate change. Driving the research is the 10ºF increase in the average annual temperature on the Antarctic Peninsula in the last 30 years, more than five times the global average.
This recent consequence of climate change is by no means the most compelling for Adélie penguins. Current levels of DDT are not sufficient to impact penguin health, Geisz says. But, she sums up some of her tissue collection for the study stating; “warmer air holds more moisture and unseasonable snows bury the penguins on their nests, freezing the eggs in puddles of ice.”
Once frozen, the eggs will never hatch. “Sad for the penguins, but good for the contaminant researcher, I suppose” utters Geisz.
Future work for Geisz includes examining penguins and other Antarctic seabird tissues for an entire suite of POPs. Contaminants more toxic than DDT are cycling in the environment, raising concerns about the potential cumulative effects of these compounds on Antarctic wildlife.