During that time iron from weathering will enter the oceans and presumably form soluble compounds.
During the Precambrian era, before the significant accumulation of oxygen in the Earth's atmosphere, oceans likely had a greenish color. This is because photosynthetic bacteria, such as cyanobacteria, were present in the oceans and used pigments like chlorophyll to capture sunlight for energy. The absence of oxygen meant that the oceans had a reducing environment, and the pigments responsible for the green color likely dominated the marine ecosystems at that time.
Dear Miloud Chakit
Thank you for your interesting answer.
I was hoping the colour would be red to account for the red colour of the blood in the first animals that appeared later on during the Precambrian and continued up to now.
Maybe there was a transition later on from green to red?
In my knowledge, during the Precambrian, before the appearance of oxygen, oceans likely had a greenish hue due to the prevalence of iron in a reduced state. The transition to a reddish color occurred as oxygen levels rose, leading to the oxidation of iron and the formation of red sediments. This shift in ocean color is evident in geological records.
Dear Miloud Chakit
Thank you for your explanation. To me it means a lot.
The oldest "red beds" according to Hongwei Kuang et al (2022) was around 2.3 b.y., but before them were some of the (BIF) Iron Formations starting as old as 3.8 b.y. The most recent BIF was around 1.8.b.y. (Wikipedia)
According to the Smithsonian the first oceans were around 4.4 b.y.
From the above, to make it simple (probably, the real story may be different)
YEARS AGO DURATION COLOUR OF OCEAN
------------ ------------- ---------------------
4.4.b.y.--3.8.b.y. 600 m.y. green
3.8 b.y. --1.8 b.y. 2.6 b.y. red
1.8 b.y. to now 1.8 b.y. colourless
(assuming that all subsequent Red Beds were terrestrial, not marine)
If the first animals were created while the ocean was red, then I would be happy to know there is a similarity between our blood and the ocean of the older days. This similarity is real as far as composition goes, but not in colour so far.
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