Accidentally discovered and rare fossilized algae close evolutionary gaps

Katie Maloney, a geobiology student, set out to discover microscopic fossils of early life in the mountains of the Canadian isolated Yukon Territory.

(Photo: Leonard Laub on Unsplash)

Even with precise terrain planning, the chances of discovering the same rocks were slim. She did not leave empty-handed. However, she returned with some of the most important fossils from that period.

Algae and oxygen production

Green ice in Antarctica

(Photo: Cambridge University)
Snow in some parts of Antarctica turns green from algal blooms that thrive in the snow. Green snow algae grow mainly on the Antarctic coast, in areas where it is warmer.

More than two billion years ago, eukaryotic life (cells with a DNA-containing nucleus) formed, and photosynthetic algae dominated the field for hundreds of millions of years as oxygen accumulated in the Earth’s atmosphere. Algae are thought to have first formed in freshwater ecosystems on land and then moved into the sea, geobiologists say. However, since fossil records from early Earth are incomplete, the exact date of the evolutionary process is not known.

Maloney’s observations were published in the journal Geology. Her team discovered macroscopic fossils of different species of algae that coexisted on the seabed about 950 million years ago, located between bacterial clusters in the shallow ocean. The discovery bridges the evolutionary division between algae and more complex life, placing time constraints on eukaryotic evolution.

Lucky Discovery

Despite the fact that the head of Maloney’s field team, sedimentologist Galen Halverson, deliberately chose the field and worked in the area for years, the finding was unlikely luck.

“Maybe we’ll find some microfossils,” Maloney speculated. She did not mention the likelihood of discovering larger fossils. “So when we started finding well-preserved bones, we put everything on hold and assembled a whole team to collect more fossils. That’s when we started to come across large, intricate plates that contained hundreds of specimens. It was really exciting!”

In paleobiology, a step is needed to determine if traces like those discovered by Maloney are biogenic (formed from living organisms). Although the final decision is made in the lab, several aspects have helped her in this area. Inside the tracks were visible patterns, which can be a positive predictor of survival. Her decision was facilitated by the fact that hundreds of them were involved.

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Unnoticed fossil

Most people certainly did not notice the fossils that day.

Marc Laflamme, Maloney’s assistant, said, “We were really lucky Katie was there to find them because at first glance they don’t really look like anything.” “Katie is used to staring at strange fossils, so it makes sense to see them and think, ‘This is something worth looking at.'”

The heavy plates were pushed into his helicopter by Maloney and her colleagues in the field for safe transport back to the University of Toronto-Mississauga lab. She, Laflamme, and their colleagues used microscopy and geochemical techniques to prove that fossils were early eukaryotes. They then accurately mapped the cellular characteristics of the samples, allowing them to distinguish different organisms in the group.

Maloney and her co-authors were convinced that they had discovered the first macroscopic samples from this crucial time frame as they recorded their findings. However, during the peer review process, they learned from a colleague that another group in China had discovered a similar discovery at the same time as macrofossils from the same era. That didn’t deter them.

“What is a couple of hundred million years between friends?” says one of the characters. Laflamme burst out laughing. “Our fossils, I believe, have more detail, which makes them easier to understand … They’re stunning. They’re massive, intricately detailed, and contain anatomy. Your eyes naturally attract them.”

Eukaryotic evolution

Chlamydomonas Reinhardtii (PICTURE)

(Photo: RIPE)
Recent research has revealed a link missing in the photosynthetic process of green algae called Chlamydomonas reinhardtii that could be used to increase crop productivity.

Finally, the possession of two collections of macrofossils from approximately the same time period will only reinforce the history of eukaryotic evolution by acting as important reference points for DNA-based biological dating techniques. The latest fossils also retain a period in which algae lived in aquatic habitats, implying that evolution was already taking place in inland lakes. According to Maloney, a sedimentologist, they also raise concerns about what is stored in the stone records and why.

“Algae were significant early on because of their role in oxygenation and biogeochemical cycles,” Maloney said. “Well, why does it take them so long to appear in fossil records? It certainly makes us think about animal populations and whether we get the full picture or lose a lot due to a lack of sustainability.”

Hoping for further discoveries

To Maloney, who switched from a newer biota to algae, the whole experiment was fascinating. “I had no idea algae could fascinate me,” she said. “But I was happily shocked when I started researching modern algae and discovered what a crucial role they play in biodiversity and climate change – all the major problems we face today. As a result, it’s amazing to play a role in algal evolution.”

Read also: Better primates? Humans have evolved to be more efficient in water than the nearest animal species

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