Ring of existence
The new data from China supported this view. It was
based on the traces left in rocks by cyanobacteria. These photosynthetic,
mostly single-celled organisms existed in vast blooms in the Permian
oceans. They are one of the major groups of phytoplankton, which
form the basis of the marine food chain.
However, the phytoplankton not eaten by higher organisms
would have fallen to the seafloor over time to be incorporated into
the sedimentary rocks seen today. And chemical components in their
cell membranes left telltale signs of their past existence.
Specifically, a lipid molecule known as 2-methylhopane
left ring structures in the Meishan rock. These ring structures form
a kind of hydrocarbon skeleton which can be preserved for a very long
time. The research team found two peaks of abundance in the Chinese
rocks which were believed to indicate periods immediately following
biotic crises in the oceans - times at which the collapse of higher
marine lifeforms allowed the cyanobacteria populations to boom.
What is theorised to have happened is that the
grazing pressure changed. A lot of the fauna that went extinct went
through larval stages that would have fed on the phytoplankton.
Changes in the faunal assemblages would have changed predation
patterns, and this led to the phytoplankton prospering.
Land of turmoil
The Permian-Triassic mass extinction killed off
about 95% of all marine species and about three-quarters of all land
families. It is the boundary at which the famous water-dwelling
arthropods known as the trilobites were wiped out.
The Permian saw the creation of the supercontinent
known as Pangea (not the planet's first supercontinent, however), and
the geological evidence suggests that this landmass experienced huge
volcanic turmoil. The Siberian Traps were built during this period -
millions of cubic kilometres of basalt lavas were spilled onto Earth's
This is the first time that scientists knew with
some certainty what was happening to the very base of the food chain
at this time. There was had no handle on plankton populations before
this because they don't fossilise, claimed Dr Paul Wignall of the
University of Leeds, who was also studying the Permian-Triassic
extinction. The study was highly interesting, because to affect the
base of the food chain takes a lot of doing. This event showed a world