[Rockhounds] A Slowdown in Earth’s Rotation Could Have Affected the Oxygen Content of the Atmosphere

[Kreigh Tomaszewski]

Virtually all oxygen on Earth was and is produced by photosynthesis, which
was invented by tiny organisms, the cyanobacteria, when our planet was
still a rather uninhabitable place. Cyanobacteria evolved more than 2.4
billion years ago, but Earth only slowly transformed to the oxygen-rich
planet we know today. “We do not fully understand why it took so long and
what factors controlled Earth’s oxygenation,“ said geomicrobiologist Judith
Klatt. “But when studying mats of cyanobacteria in the Middle Island
Sinkhole in Lake Huron in Michigan, which live under conditions resembling
early Earth, I had an idea.”
Klatt worked together with a team of researchers around Greg Dick from the
University of Michigan. The water in the Middle Island Sinkhole, where
groundwater seeps out of the lake bottom, is very low in oxygen. “Life on
the lake bottom is mainly microbial, and serves as a working analog for the
conditions that prevailed on our planet for billions of years,” says Bopi
Biddanda, a collaborating microbial ecologist from the Grand Valley State
University. The microbes there are mainly purple oxygen-producing
cyanobacteria that compete with white sulfur-oxidizing bacteria. The former
generate energy with sunlight, the latter with the help of sulfur.
In order to survive, these bacteria perform a tiny dance each day: From
dusk till dawn, the sulfur-eating bacteria lie on top of the cyanobacteria,
blocking their access to sunlight. When the sun comes out in the morning,
the sulfur-eaters move downwards and the cyanobacteria rise to the surface
of the mat. “Now they can start to photosynthesize and produce oxygen,”
explained Klatt. “However, it takes a few hours before they really get
going, there is a long lag in the morning. The cyanobacteria are rather
late risers than morning persons, it seems.” As a result, their time for
photosynthesis is limited to only a few hours each day. When Brian Arbic, a
physical oceanographer at the University of Michigan, heard about this diel
microbial dance, he raised an intriguing question: “Could this mean that
changing daylength would have impacted photosynthesis over Earth’s history?”

https://scitechdaily.com/a-slowdown-in-earths-rotation-could-have-affected-the-oxygen-content-of-the-atmosphere/