Scientists discover vast underground ecosystem of 'deep life' microbes

The video discusses the discovery of an underground biosphere 2.5 kilometers below the seabed, filled with ancient microbes. These lifeforms thrive in extreme conditions, feeding on energy from rocks. It is suggested that 70% of Earth's bacteria and archaea exist underground, contributing significantly to the planet's carbon. Unique microorganisms, such as those living in sulphuric springs and hydrothermal vents, are highlighted for their ability to grow at high temperatures.

What percentage of Earth's bacteria and archaea are believed to exist underground?

What is the significance of the carbon amount found in the underground biosphere?