British researchers have hit on a clever way to search for ancientozone holes and their relationship to mass extinctions: measure theremains of ultraviolet-B absorbing pigments ancient plants left intheir fossilized spores and pollen.
To develop the approach, researcher Barry Lomax and his colleaguesat the University of Sheffield and other leading UK institutionsanalyzed spores held in the British Antarctic Survey's collection fromSouth Georgia Island, a UK territory in the far southwestern corner ofthe Atlantic Ocean. They discovered that since the 1960s, spores fromliving land plants have shown a three-fold increase in theconcentration of UV-B absorbing pigments to protect themselves againsta 14 percent decrease in stratospheric ozone, says Lomax.
"We have initially been investigating whether plants ofpalaeobotanical significance are capable of adapting to changes in UV-Bradiation," said Lomax. In particular, they studied the UV-B responseof the club moss Lycopodium magellanicum, a native of South GeorgiaIsland.
"Now that this has been established we are investigatingpossible changes in terrestrial UV-B flux during the Permian-Triassicboundary (251 million years ago)," said Lomax. That boundary marks thelargest mass extinction in the Earth's history and also coincides withthe largest known eruption of lava and potentially ozone-destroyinggases - the Siberian Traps.
The latest results from the ongoing work will be presented byLomax on Wednesday, 10 August, at Earth System Processes 2, a meetingco-convened by the Geological Society and Geological Association ofCanada this week in Calgary, Alberta, Canada.
The modern increase in UV-B at South Georgia is the directresult of high latitude springtime ozone destruction in thestratosphere caused by decades of releases of human-madechlorofluorocarbons (CFCs). The situation may have been the same aquarter billion years ago, except that the earlier ozone-destroyingchemicals came from the Earth itself.
"Volcanic eruptions can emit gases such as chlorine andbromine that are capable of destroying ozone," said Lomax. The heatingof rocks near volcanic flows of the Siberian Traps may also release awide range of organohalogens thought to be harmful to ozone, he said.
The next step is to search for the chemical remains of theplant pigments in fossilized spores and pollen. "The pigments breakdown to form compounds that are stable over geological time," saidLomax, "so providing samples have not been subjected to large amountsof heat, the signature should be preserved."
The research is funded by the UK's Natural Environment ResearchCouncil, with the specific aim of finding a way to measure ancient UV-Blevels by combining experimental and palaeobotanical investigations.
The Siberian Traps, Stratospheric Ozone, UV-B Flux, and Mutagenesis
Wednesday, 10 August, 10:00 a.m. MDT, Lakeview Endrooms
Calgary Westin Hotel
Abstract may be viewed athttp://gsa.confex.com/gsa/2005ESP/finalprogram/abstract_88582.htm
During The Earth System Processes 2 meeting, 8-11 August,contact Ann Cairns at the ESP2 Newsroom, Calgary Westin Hotel, forassistance and to arrange for interviews: 1-403-508-5135.
After the meeting, contact:
Department of Animal and Plant Sciences
University of Sheffield
Geological Society of America
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