Pre-Phanerozoic CO2 levels and pluricell life influence in C Earth's cycle

Question

This graph presents an estimate of Phanerozoic CO₂ levels on Earth.

From the onset of the graph, it appears that CO₂ levels are rising. However, I've come across papers, such as this one, suggesting that Proterozoic CO₂ levels were higher than those in the Phanerozoic.

I'm seeking a summary of how multicellular life has influenced Earth's CO₂ levels to better understand our planet. I recognize that this topic is vast and could span an entire book. So, to narrow it down:

I understand that both foraminifera and other unicellular and multicellular organisms have been storing CO₂ since the beginning of the Phanerozoic.

On the other hand, multicellular organisms, especially plants, have acted as CO₂ sinks. This began during the Devonian-Carboniferous period. However, data suggests a declining CO₂ trend since the Cambrian. This leads me to believe that the decrease in atmospheric CO₂ throughout half of the Phanerozoic might be mainly attributed to shell-forming organisms. This brings me to a central question:

Which organisms have removed more CO₂ in Phanerozoic and in total Earth's history, plants or shell organisms?

Additionally, I'd appreciate it if you could answer this other related question I've posted with a bounty.

Answer 1

It changes, there is no one overwhelming effect.

At some times plants have dominated at others ocean sediments have dominated. Position of continents, global temperature, sea level, and evolution of lifeforms all effect it.

Also you have a problem that those time periods are time PERIODS, the Proterozoic is 5 times longer than the phanerozoic. It had higher AND lower levels.

https://rock.geosociety.org/net/gsatoday/archive/9/11/pdf/i1052-5173-9-11-1.pdf

https://earthscience.rice.edu/wp-content/uploads/2017/08/Berner_nature-2003-1.pdf

https://www.sciencedirect.com/science/article/pii/S1342937X18302818