Oceans' Toxicity Changed Evolution Of Complex Life: Study Reveals New Findings
A team of international researchers examined rocks from the bottom of ancient oceans, which revealed that oceans had a long history of toxic and arsenic concentrations, which varied over the years, according to a study from Stockholm University. The researchers found that early oceans had varying levels of arsenic, which changed gradually as oxygen levels increased in the atmosphere along with the coming and going global glaciations.
"In the article we argue that when we first see the appearance of complex life on Earth, is when life have developed mechanisms to resist catastrophic chemical changes forced by global glaciations," Dr. Ernest Chi Fru, lead author of the study, said in a news release. "This enabled the expansion of complex life in oceans, and paved the way for our own evolution."
Oxygen first appeared in the atmosphere when marine arsenic concentrations were quite low, which was after 2.45 billion years ago, according to the researchers. Around this time, the earth had its first global glaciation. When these glaciations ended, there was an increase in marine arsenic concentrations, which resulted in a reduction of atmospheric oxygen.
The researchers claimed that the reactions of modern photosynthetic organism towards the varying marine arsenic concentrations indicated that ocean toxicity was caused by the release of toxic elements when the ice melted.
The researchers found that high and low arsenic levels were associated with global glaciations 0.7 billion years ago, when the earth had its first development of complex life. Low levels of marine arsenic concentrations coincided with an increase of atmospheric oxygen near modern times.
As the ice melted, the increase of marine arsenic concentrations was not accompanied by a reduction in atmospheric oxygen, according to the researchers.
The findings of this study were published in Scientific Reports.
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