Nitrogen takes center stage in the Great Oxygenation Event

Altering the known path of evolution?

Algae making bubbles of O2 in a South African lake.

 

Research fresh from the University’s own School of Earth and Environmental Science provides fresh insight into a key part of Earth’s evolution. This new take on The Great Oxygenation Event by the team headed by Dr. Aubrey Zerkle is based on new data that fills a 400 million year gap in the Nitrogen isotope record left by previous research. This data can now be better used to assign a time frame for the oxygenation of the Oceans. This research resonates in many areas of Earth Science, both on Earth and in our own solar system.

The great event

Dr. Zerkle and colleague Dr. Mark Claire pond more than 2 billion years of Earth history, preserved in rock cores stored at the National Core Library, Donkerhoek, South Africa

The Great Oxygenation Event can, in basic terms, be described as a large increase in atmospheric oxygen levels, which later led to the oxygenation of the oceans. This provided the environment for other life to evolve, in what has been described as the most dramatic environmental change in Earth’s history. This had consequences for many delicate cycles going on in the early Earth, like for instance the Nitrogen cycle. The importance of nitrogen in the early Earth cannot be understated. It is a crucial component required for all RNA, DNA and the formation of proteins and amino-acids. It is also responsible for regulating the amount of oxygen at the Earth’s surface.

 

 

 

 

 

Outcrop pics from the Duitschland Formation, which underlies the Rooihoogte and Timeball Hill formations in the Eastern Transvaal basin, South Africa.

The research and what it means for our planet

Dr. Zerkle explained: “Our data shows the first occurrence of widespread nitrate, which could have stimulated the rapid diversification of complex organisms, hot on the heels of global oxygenation. The building blocks were apparently in place, the question that remains is why eukaryotic evolution was seemingly stalled for another billion or more years.”

Catastrophic upheavals in past surface conditions such as these provide a critical window for Earth scientists to study how the biosphere responds to environmental change. Understanding how life on this planet responded to geochemical changes in the past will help us to more clearly predict the response to future changes, including Earth’s warming climate. It will also inform our search for habitable planets in other solar systems.”

 

If not the Paleoproterozoic, then when? 

This research mirrors the findings of a similar study, also carried out by the University of St Andrews, by Dr. Eva Stüeken. This focused on the Selenium cycle and found a distribution that corroborates a large expansion in Oxygen at the Earths surface Ocean. This rise in Oxygen could explain the nitrate deposits from the period, and even the evolution of life. Dr. Andrey Bekker from UC-Riverside, who co-authored both studies, explained: “We now know that redox conditions were favourable for complex life to evolve immediately after the Great Oxidation Event”. But like many scientific discoveries, this paper leads to more questions: as Dr. Bekker outlines. “The question is if eukaryotes did not evolve in the early Paleoproterozoic, what are the other intrinsic controls that determine the evolution of life?

 

 

 

Photo credits

All photos © Aubrey Zerkle

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