Saturday, August 13, 2005

Ancient Ozone Holes and Mass Extinctions

This blog is, primarily, about evolution. Whenever possible I like to publish stories about some of the interesting techniques scientists use to learn things about the past. This is another along those lines.

Lycopodium magellanicum is a species of clubmoss native to South America, and islands in the southern Atlantic and Indian oceans.

The leaves are arranged in cones which bear sporangia containing spores of one type only.

Reserchers examined the spores of Lycopodium magellanicum for UV-B screening pigments. The idea being that as the ozone layer thins an increase in UV-B screening pigments should be observed. This is exactly what they found. Basically this first step was a test to see if the methodology (examining spores for UV-B screening pigments) would yeild results relevant to the question of whether or not we can detect ozone depletion in the past. Having answered the question in the affirmative, the researchers are turning their attention to the Permian-Triassic boundry some 250 million years ago (I should mention that the chemical traces of UV-B screening pigments can be detected in the geological record).
One of the important events, geologically speaking, to occur around the end of the Permian was the volcanic eruption of the Siberian traps, a byproduct of which is the destruction of the ozone layer. Hypothetically, this would mean we should detect an increase in UV-B screening pigments in spores from that time period.

For more info:


New Window Into Ancient Ozone Holes

Permian Extinction

Rocks Reveal Details of Mass Extinction