BROADCASTS.com

One of the most significant events in Earth\u2019s history has been the\xa0oxygenation of its atmosphere 2.45\u20132.32 billion years ago.\xa0This accumulation of molecular oxygen in Earth\u2019s atmosphere was\xa0so significant that it is now commonly known as the\xa0Great Oxidation\xa0Event\xa0(GOE). The long-reaching effects of the GOE were\xa0literally world-changing; the compositions of the\xa0atmosphere and hydrosphere were altered, and through various redox reactions (where atoms have their oxidation state changed),\xa0the nature of the continents and global climate changed too. However, and perhaps from an\xa0anthropocentric viewpoint, the most important effect would be upon\xa0the biosphere: the GOE paved the way for the evolution of aerobic\xa0(oxygen respiring) organisms, including our earliest ancestors.

It is possible to track the GOE through geochemical traces left in the rock record. However, one thing we're still uncertain about is whether or not this event represents either a\xa0sharp increase in oxygen production or a reduction in oxygen sinks - the jury is still out on that one. With this level of ambiguity over the\xa0dynamics of the GOE, it may be a little surprising to know that there has been a long-standing consensus on how the oxygen was actually produced:\xa0photosynthetic organisms called cyanobacteria (blue-green\xa0algae, so named after the pigment they produce).

In this episode we discuss with Dr. Bettina Schirrmeister (University of Bristol) about the evolution of cyanobacteria and the role they played in the GOE.