A study into Lake Superior has revealed a 3 billion-year-old secret about planet Earth.
Researchers at the University of California, Santa Barbara, and University of Minnesota, Duluth, discovered a new type of sulfur cycle in Lake Superior, the largest freshwater lake in the world. And this is going to give scientists insight into the biochemistry of Earth's ancient ocean.
"It's really hard to look back billions of years," Phillips, a former postdoctoral researcher at the universities said in a news release detailing the findings. "So this is a great window."
Sulfur is an important macronutrient, a chemical that sustains plant growth. It is one of the most abundant elements found in seawater.
The researchers found that Lake Superior contained little sulfate. This makes it very similar to the world's ancient oceans, as it contains a thousand times less than what we see in the modern oceans today. Ancient oceans typically contained less sulfate because of the lack of free oxygen.
"In terms of sulfate, Lake Superior looks a lot closer to the ocean billions of years ago and may help us understand processes we can't go back in time to observe directly," Phillips said.
This means the lake provides a great example on what the world's ancient oceans may have been like. This allows scientists to analyze the sulfur cycle, gaining better insight into how it would have been billions of years ago.
"For a long time, our thinking was dominated by what we could learn from modern oceans, which are sulfate-rich," senior author of the study Sergei Katsev, a professor at University of Minnesota's Large Lakes Observatory, said in the release. "Understanding early Earth, however, requires looking at processes that emerge when sulfate is scarce, and this is where organic sulfur can change the whole paradigm."
Throughout the study, scientists found that organic sulfur serves as an energy source for microorganisms.
Combined, these factors could help scientists understand the evolution of early sulfur-cycling microorganisms and their impact on Earth's chemistry.
"Organic sulfur cycling, like what we see in Lake Superior, is probably ubiquitous in marine and freshwater sediments. But in the ocean sulfate is so abundant that its behavior swamps out most of our signals," another senior author of the study, Morgan Raven, and biogeochemist at UC Santa Barbara, said in a release. "Working in low-sulfate Lake Superior lets us see how dynamic the sedimentary organic sulfur cycle really is."
Lake Superior itself is actually one of the earth's younger features. It only formed around 10,000 years ago, which is relatively young in context with other lakes and oceans.
About the writer
Robyn White is a Newsweek Nature Reporter based in London, UK. Her focus is reporting on wildlife, science and the ... Read more
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