A scuba diver observes the purple, white and green microbes covering rocks in Lake Huron’s Middle Island Sinkhole. Credit: Phil Hartmeyer, NOAA Thunder Bay National Marine Sanctuary.
The rise of oxygen levels early in Earth’s history paved the way for the spectacular diversity of animal life. But for decades, scientists have struggled to explain the factors that controlled this gradual and stepwise process, which unfolded over nearly 2 billion years.
Now an international research team is proposing that increasing day length on the early Earth—the spinning of the young planet gradually slowed over time, making the days longer—may have boosted the amount of oxygen released by photosynthetic cyanobacteria, thereby shaping the timing of Earth’s oxygenation.
Their conclusion was inspired by a study of present-day microbial communities growing under extreme conditions at the bottom of a submerged Lake Huron sinkhole, 80 feet below the water’s surface. The water in the Middle Island Sinkhole is rich in sulfur and low in oxygen, and the brightly colored bacteria that thrive there are considered good analogs for the single-celled organisms that formed mat-like colonies billions of years ago, carpeting both land and seafloor surfaces.
The researchers show that longer day length increases the amount of oxygen released by photosynthetic microbial mats. That finding, in turn, points to a previously unconsidered link between Earth’s oxygenation history and its rotation rate. While the Earth now spins on its axis once every 24 hours, day length was possibly as brief as 6 hours during the planet’s infancy.
The team’s findings are scheduled for publication Aug. 2 in the journal Nature Geoscience.
Lead authors are Judith Klatt of the Max Planck Institute for Marine Microbiology and Arjun Chennu of the Leibniz Centre for Tropical Marine Research. Klatt is a former postdoctoral researcher in the lab of University of Michigan geomicrobiologist Gregory Dick, who is one of the study’s two corresponding authors. The other co-authors are from U-M and Grand Valley State University.
“An enduring question in the Earth sciences has been how did Earth’s atmosphere get its oxygen, and what factors controlled when this oxygenation took place,” Dick said from the deck of the R/V Storm, a 50-foot NOAA research vessel that carried a team of scientists and scuba divers on a sample-collection trip from the town of Alpena, Michigan, to the Middle Island Sinkhole, several miles offshore.
“Our research suggests that the rate at which the Earth is spinning—in other words, its day length—may have had an important effect on the pattern and timing of Earth’s oxygenation,” said Dick, a professor in the U-M Department of Earth and Environmental Sciences.
The researchers simulated the gradual slowing of Earth’s rotation rate and showed that longer days would have boosted the amount of oxygen released by early cyanobacterial mats in a manner that helps explain the planet’s two great oxygenation events.
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The project began when co-author Brian Arbic, a physical oceanographer in the U-M Department of Earth and Environmental Sciences, heard a public lecture about Klatt’s work and noted that day length changes could play a role, over geological time, in the photosynthesis story that Dick’s lab was developing.
Cyanobacteria get a bad rap these days because they are the main culprits behind the unsightly and toxic algal blooms that plague Lake Erie and other water bodies around the world.
But these microbes, formerly known as blue-green algae, have been around for billions of years and were the first organisms to figure out how to capture energy from sunlight and use it to produce organic compounds through photosynthesis—releasing oxygen as a byproduct.
Masses of these simple organisms living in primeval seas are credited with releasing oxygen that later allowed for the emergence of multicellular animals. The planet was slowly transformed from one with vanishingly small amounts of oxygen to present-day atmospheric levels of around 21%.
At the Middle Island Sinkhole in Lake Huron, purple oxygen-producing cyanobacteria compete with white sulfur-oxidizing bacteria that use sulfur, not sunlight, as their main energy source.
In a microbial dance repeated daily at the bottom of the Middle Island Sinkhole, filmy sheets of purple and white microbes jockey for position as the day progresses and as environmental conditions slowly shift. The white sulfur-eating bacteria physically cover the purple cyanobacteria in the morning and evening, blocking their access to sunlight and preventing them from carrying out oxygen-producing photosynthesis.
But when sunlight levels increase to a critical threshold, the sulfur-oxidizing bacteria migrate back down below the photosynthetic cyanobacteria, enabling them to start producing oxygen.
This June 19, 2019 photo provided by NOAA Thunder Bay National Marine Sanctuary shows purple microbial mats in the Middle Island Sinkhole in Lake Huron, Mich. Small hills and “fingers” like this one in the mats are caused by gases like methane and hydrogen sulfide bubbling up beneath them. Feel like days are just getting longer? They are and it’s a good thing because we wouldn’t have much to breathe if they weren’t, according to a new explanation for how Earth’s oxygen rich atmosphere may have developed because of Earth’s rotation slowing. Scientists provided evidence for this new hypothesis by lab testing gooey smelly purple bacteria from a deep sinkhole in Lake Huron. Credit: Phil Hartmeyer/NOAA Thunder Bay National Marine Sanctuary
The vertical migration of sulfur-oxidizing bacteria has been observed before. What’s new is that the authors of the Nature Geoscience study are the first to link these microbial movements, and the resultant rates of oxygen production, to changing day length throughout Earth’s history.
“Two groups of microbes in the Middle Island Sinkhole mats compete for the uppermost position, with sulfur-oxidizing bacteria sometimes shading the photosynthetically active cyanobacteria,” Klatt said while processing a core sample from Middle Island Sinkhole microbial mats in an Alpena laboratory. “It’s possible that a similar type of competition between microbes contributed to the delay in oxygen production on the early Earth.”
A key to understanding the proposed link between changing day length and Earth’s oxygenation is that longer days extend the afternoon high-light period, allowing photosynthetic cyanobacteria to crank out more oxygen.
“The idea is that with a shorter day length and shorter window for high-light conditions in the afternoon, those white sulfur-eating bacteria would be on top of the photosynthetic bacteria for larger portions of the day, limiting oxygen production,” Dick said as the boat rocked on choppy waters, moored a couple hundred yards from Middle Island.
The present-day Lake Huron microbes are believed to be good analogs for ancient organisms in part because the extreme environment at the bottom of the Middle Island Sinkhole likely resembles the harsh conditions that prevailed in the shallow seas of early Earth.
Lake Huron is underlain by 400-million-year-old limestone, dolomite and gypsum bedrock that formed from the saltwater seas that once covered the continent. Over time, the movement of groundwater dissolved some of that bedrock, forming caves and cracks that later collapsed to create both on-land and submerged sinkholes near Alpena.
Cold, oxygen-poor, sulfur-rich groundwater seeps into the bottom of the 300-foot-diameter Middle Island Sinkhole today, driving away most plants and animals but creating an ideal home for certain specialized microbes.
Dick’s team, in collaboration with co-author Bopaiah Biddanda of the Annis Water Resources Institute at Grand Valley State University, has been studying the microbial mats on the floor of Middle Island Sinkhole for several years, using a variety of techniques. With the help of scuba divers from NOAA’s Thunder Bay National Marine Sanctuary—which is best known for its shipwrecks but is also home to the Middle Island Sinkhole and several others like it—the researchers deployed instruments to the lake floor to study the chemistry and biology there.
They also brought mat samples to the lab to conduct experiments under controlled conditions.
Klatt hypothesized that the link between day length and oxygen release can be generalized to any given mat ecosystem, based on the physics of oxygen transport. She teamed up with Chennu to conduct detailed modeling studies to relate microbial mat processes to Earth-scale patterns over geological timescales.
The modeling studies revealed that day length does, in fact, shape oxygen release from the mats.
“Simply speaking, there is just less time for the oxygen to leave the mat in shorter days,” Klatt said.
This led the researchers to posit a possible link between longer day lengths and increasing atmospheric oxygen levels. The models show that this proposed mechanism might help explain the distinctive stepwise pattern of Earth’s oxygenation, as well as the persistence of low-oxygen periods through most of the planet’s history.
Throughout most of Earth’s history, atmospheric oxygen was only sparsely available and is believed to have increased in two broad steps. The Great Oxidation Event occurred about 2.4 billion years ago and has generally been credited to the earliest photosynthesizing cyanobacteria. Nearly 2 billion years later a second surge in oxygen, known as the Neoproterozoic Oxygenation Event, occurred.
Earth’s rotation rate has been slowly decreasing since the planet formed about 4.6 billion years ago due to the relentless tug of the moon’s gravity, which creates tidal friction.
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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.
That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.
“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”
The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.
Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.
Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.
Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.
Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.
Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.
“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”
The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.
North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.
Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”
Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.
Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.
For Dello, the “fingerprints of climate change” were clear.
“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”
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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.
On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.
They call it “Big Sam.”
The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.
It didn’t die alone.
“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.
She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”
“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.
The head alone, she said, is about the size of a baby elephant.
The discovery was a long time coming.
The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.
“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.
When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”
“It contains about 100 to 300 bones per square metre,” she said.
Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.
About a year ago, they found the second adult: Big Sam.
Bamforth said both dinosaurs are believed to have been the elders in the herd.
“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.
“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”
The genders of the two adults are unknown.
Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.
The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.
She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.
“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.
“It’s pretty exciting.”
This report by The Canadian Press was first published Sept. 25, 2024.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
![New theory: Earth's longer days kick-started oxygen growth](https://scx1.b-cdn.net/csz/news/800a/2021/new-theory-earths-long.jpg "This June 19, 2019 photo provided by NOAA Thunder Bay National Marine Sanctuary shows purple microbial mats in the Middle Island Sinkhole in Lake Huron, Mich. Small hills and "fingers" like this one in the mats are caused by gases like methane and hydrogen sulfide bubbling up beneath them. Feel like days are just getting longer? They are and it's a good thing because we wouldn't have much to breathe if they weren't, according to a new explanation for how Earth's oxygen rich atmosphere may have developed because of Earth's rotation slowing. Scientists provided evidence for this new hypothesis by lab testing gooey smelly purple bacteria from a deep sinkhole in Lake Huron. Credit: Phil Hartmeyer/NOAA Thunder Bay National Marine Sanctuary")
