"Phosphorus ultimately limits net primary productivity on geological timescales," said Plavansky. "High marine phosphorus levels would have facilitated a shift to a more oxygen-rich ocean-atmosphere system. This shift could have paved the way for the rise of animals and their ecological diversification."
Planavsky explained the link between marine phosphorus concentrations and the levels of oxygen in the atmosphere.
"High phosphorus levels would have increased biological productivity in the ocean and the associated production of oxygen by photosynthesis," he said.
Much of this organic matter is consumed, in turn, as a result of respiration reactions that also consume oxygen. However, the burial of some proportion of the organic matter results in a net increase of oxygen levels in the atmosphere.
Until now, scientists believed that geochemical conditions in the iron-rich ocean would have led to low phosphorus concentrations.
The researchers discovered no evidence of a phosphorus crisis after Snowball Earth glacial events, however, finding instead indications of an abundance of phosphorus.
"There are several known chemical fingerprints for increasing oxygen in the ocean and, by inference, in the atmosphere during the middle part of Neoproterozoic, and the rise of animals is an expected consequence," said Timothy Lyons, a biogeochemist at UC Riverside and the senior investigator in the study.
"These results may be the first to capture the nutrient driver that was behind this major step in the history of life. That driver was ultimately tied to the extreme climate of the period."
The scientists present data from some 700 individual samples of iron-oxide-rich rocks, which include new results as well as those obtained from a comprehensive survey of the literature.
|Contact: Cheryl Dybas|
National Science Foundation