Glaciers in Antarctica may be releasing ddt through meltwaterGlobal use of the pesticide DDT has been sharply curtailed since the 1970s, so it’s natural to expect that over time, less of it would find its way into living creatures. Not so among Adelie penguins in the Western Antarctic Peninsula, however, according to a study in the journal Environmental Science and Technology. DDT levels in these birds have remained about the same in the past 30 years, and the researchers say it’s likely that Antarctic glaciers, which would have accumulated DDT through atmospheric deposition before its use was restricted, are delivering the pesticide into the food chain through meltwater. The lead author, Heidi N. Geisz of the Virginia Institute of Marine Science of the College of William and Mary, said that the purpose of the study “was not to further vilify DDT.” The findings, she said, may help in studying the persistence of organic pollutants like PCBs. Geisz and colleagues analysed penguin carcasses and eggs for levels of DDT and DDE, which is produced when DDT is metabolised. They found that the ratio of DDT to DDE declined over the years, indicating that the pesticide sources were predominantly old, having already been metabolised in the food chain. But the presence of some unmetabolized DDT in the samples suggests a fresh source. By contrast, tissue samples from McMurdo Sound, 2,000 miles away, contained only DDE. Scientists document bustling community far below ocean floorThe lost civilization of Atlantis may just be legend, but way down below the ocean there are some things that are very real—namely, bacteria and archaea. By some estimates, sub-seafloor prokaryotes may account for two-thirds of the biomass of these types of organisms on Earth. The latest evidence for such a huge undersea biosphere, and a depth record of sorts, is reported in Science by R. John Parkes of Cardiff University and colleagues. They have found living prokaryotes 5,335 ft below the ocean floor off Newfoundland, about twice as deep as the previous record. Intact cells were found in cores drilled through sediments up to 111 million years old, although the age of the prokaryotes themselves is an open question. The researchers were able to amplify genetic material, which strongly suggests that the cells are living, feeding on trapped methane, other hydrocarbons and organic carbon. Temperatures of the deepest core samples were estimated from 140 degrees to 212 degrees Fahrenheit, so the cells qualify as extremophiles, able to withstand harsh conditions like those found around deep-sea hydrothermal vents. (NYT)
