Deep-Sea Sediments Reveal a Hidden World of Life Regulating Earth’s Climate
The deep-ocean floor is far more alive and diverse than scientists previously realized, according to a groundbreaking new study. Researchers who sequenced DNA from sediments across the globe discovered that the seafloor holds at least three times more life than upper ocean layers — and nearly two-thirds of that life remains formally unidentified.
A Vast Reservoir of Hidden Diversity
“It’s been known since the 1960s that species diversity is very high in the deep sea,” said co-author Andrew Gooday, a deep-sea biologist at the National Oceanography Centre in England. “What was new about this study was that there was a lot of novel diversity at the higher taxonomic level.”
In other words, many undiscovered evolutionary lineages — not just species, but entire families and orders — await classification. This finding highlights how little we know about ecosystems that cover more than half of Earth’s surface.
How the Study Was Conducted
From 2010 to 2016, scientists collected 418 sediment samples from all major ocean basins. They compared seafloor DNA with existing genetic data from the water column to distinguish between organisms native to the sediments and remains of organisms that sank from above. Instead of identifying species directly, the team analyzed sequence variants, or distinct DNA patterns, to group organisms into broader taxonomic categories.
The majority of these variants could not be linked to any known lineage, suggesting that vast numbers of organisms — especially tiny animals less than a millimeter long and single-celled protozoans — have yet to be described. Larger organisms like octopuses were excluded, meaning the real biodiversity is likely even greater.
Why the Seafloor Hosts Such Abundance
The deep ocean provides a mosaic of microhabitats, from coral reefs to hydrothermal vents, fostering specialization and diversity. “If you have a very uniform environment, all species are exposed to the same habitat,” Gooday explained. “But if that habitat is divided into lots of microhabitats, then species can specialize.”
The Climate Connection: The Biological Pump
Beyond biodiversity, the study shed light on the deep ocean’s role in Earth’s climate system. Through the biological pump, surface organisms such as phytoplankton absorb carbon dioxide from the atmosphere. When they die, they sink to the seafloor, locking away carbon in sediments. The research revealed that the strength of this pump can be predicted based on the DNA makeup of deep-sea communities, meaning some plankton groups are more effective than others in regulating the planet’s climate.
Looking Forward
This research underscores the deep ocean’s importance as both a biodiversity hotspot and a climate regulator. Yet it also highlights how much remains unknown. As scientists continue to explore seafloor habitats, they expect to uncover entire branches of life that could reshape our understanding of evolution — and of how Earth’s hidden ecosystems sustain a stable climate.
