Take heart! Organic life on Earth will continue for millions of years even if the organic life on the surface of Earth is wiped out by cataclysms. There is a huge amount of biomass at the bottom of oceans and even beneath the oceans.
It is estimated that 1/3 of the biomass on Earth is buried under the oceans. Organisms known as intraterrestrials live beneath the bottom of the oceans. Some live in the mud beneath the seafloors; others live hundreds of meters down in fractures of rock.
On 17 March 2013, researchers reported that microbial life forms thrive in the Mariana Trench (central west Pacific Ocean). This 36,000-foot-deep (11,000 m) trench is the deepest known point on Earth’s surface.
Other researchers reported that micro-organisms live inside rocks up to 1900 feet (580 meters) below the sea floor under 8500 feet (2590 meters) of ocean off the coast of the northwestern United States. These microbes (bacteria) apparently live off energy from chemical reactions between water and rock instead of nutrients snowing from above.
Knowing that an entire ecosystem exists beneath the ocean floor gives me a good feeling. Scientists call this ecosystem the dark biosphere which may be, potentially, one of the biggest ecosystems on the planet.
C.R. Smith and A.W.J. Demopoulos, “The Deep Pacific Ocean Floor”