[Source: ScienceDaily] – More than two and a half billion years ago, Earth differed greatly from our modern environment, specifically in respect to the composition of gases in the atmosphere and the nature of the life forms inhabiting its surface. While today’s atmosphere consists of about 21 percent oxygen, the ancient atmosphere contained almost no oxygen. Life was limited to unicellular organisms. The complex eukaryotic life we are familiar with — animals, including humans — was not possible in an environment devoid of oxygen.
The life-supporting atmosphere Earth’s inhabitants currently enjoy did not develop overnight. On the most basic level, biological activity in the ocean has shaped the oxygen concentrations in the atmosphere over the last few billion years. In a paper published August 23 by Nature Geoscience online, Arizona State University researchers Brian Kendall and Ariel Anbar, together with colleagues at other institutions, show that “oxygen oases” in the surface ocean were sites of significant oxygen production long before the breathing gas began to accumulate in the atmosphere.
For more information: Ancient Microbes Responsible for Breathing Life Into Ocean ‘Deserts’