A recent study conducted by Japanese researchers has revealed a fascinating new theory about the Earth’s oceans billions of years ago. The study suggests that the oceans were not blue, as they are today, but rather a vibrant green.
The Link Between Iron and Ocean Color
The study, published in Nature, focuses on a critical period in Earth’s history: the Archaean eon, which took place between 3.8 and 1.8 billion years ago. During this time, the atmosphere and oceans were devoid of oxygen. Scientists had long believed that the Earth’s oceans were blue, even during the early stages of its formation.
Japanese researchers from Nagoya University have discovered something different. According to the study, the oceans of this era were likely green due to the presence of high levels of iron, particularly oxidized iron.
Why Blue-Green Algae Were Essential for Life’s Beginnings?
The discovery was initially prompted by the unique environmental conditions surrounding Iwo Jima, a volcanic island in the Ogasawara Archipelago. Researchers noticed that the waters there had a greenish tint, which was later linked to the presence of blue-green algae or cyanobacteria.
These microorganisms thrive in iron-rich environments and play a key role in photosynthesis. The algae’s ability to perform photosynthesis in such environments allowed them to sustain life in the absence of oxygen.
Cyanobacteria: The Pioneers of Early Photosynthesis
“Blue-green algae, a meeting of the two colors, also called cyanobacteria, have existed for about 3.5 billion years. They were among the first organisms to perform photosynthesis using ferrous iron to source their electrons. The byproduct was oxygen,” states the article from Interesting Engineering.
This process of anaerobic photosynthesis, in which cyanobacteria used ferrous iron for energy, resulted in the gradual buildup of oxygen. The oxygen released into the atmosphere would later trigger the “great oxidation event,” a pivotal moment in Earth’s history that eventually led to the rise of more complex life forms.
The Green Ocean Hypothesis
The theory that the oceans were once green is further supported by the chemical composition of cyanobacteria. These organisms contain a pigment known as phycoerythrobilin (PEB), which helps them capture light. Unlike chlorophyll, the green pigment found in most plants and algae, PEB gave these organisms the ability to thrive in the iron-rich waters of the early Earth.
Japanese scientists took this theory a step further by genetically engineering cyanobacteria to include PEB, and to their surprise, the algae grew better in green-colored waters. This experiment confirmed that the green hue of the ocean was not only possible but also likely during the Archaean eon.
What Could This Mean for the Future?
“Will the ocean turn purple?” This is an intriguing question raised by the study. As the sun ages and its energy output increases, scientists speculate that Earth’s oceans could change color again.
Some researchers predict that the oceans could even turn purple or red, depending on the specific chemical changes in the atmosphere and the environment. Before this happens, Earth’s oceans are expected to evaporate as the sun reaches the end of its life cycle.
Source: The Daily Galaxy / Digpu NewsTex