As the deep ocean faces growing peril from climate change, seabed mining and other threats, scientists have discovered that seafloor sediments are home to vast populations of previously unknown organisms that may play a crucial role in carbon sequestration and marine food webs.

When researchers analysed DNA sequences taken from sediment samples from around the world, they were astonished to find that nearly two thirds were new to science, representing entire families of undescribed life forms, according to a study published on February 4 in the journal Science Advances...