Though the deep ocean covers more than half the planet, we know more about the surface of the moon than about life in the far recesses of the sea. But a new study shows just how vital the deep ocean—defined as depths beyond 200 meters, or 656 feet—is for storing atmospheric carbon, nutrient recycling, and marine life support.
But the deep ocean also holds vast quantities of valuable minerals and metals, such as manganese and cobalt, making it a target for corporations aiming to mine it. The United Nation-chartered International Seabed Authority, which controls activity on the seafloor, has awarded contracts with nations in the central Pacific to explore the deep ocean for metals.
“Deep-sea habitats receive much less attention than environments closer to home, as they are inhospitable to humans, remote and there are numerous challenges associated with studying this environment directly,” the authors of the study wrote in the paper, which was published in the journal Biogeosciences. “As a result, this has delayed the acknowledgment of the vitally important ecosystem functions and services the deep sea provides.”
“Unfortunately, this comes at a time when services from the deep sea are in increasing demand and [it is] under great pressure for its products,” they added.
In response, a group of scientists, lawyers, and policy makers formed Deep Ocean Stewardship Initiative.
Founded in 2013, DOSI aims to help regulators make science-sound decisions.
“We want to make sure that before massive commercial exploitation happens in the deep oceans, there are discussions about the services and functions of those ecosystems—how to protect them, whether we need protected areas, how to apply precautionary principles, how to bring in economic and ecological considerations before drastic changes happen,” said Lisa Levin, director of the Center for Marine Biodiversity and Conservation and a leader of DOSI.
DOSI is studying the impact of dumping mine tailings—the toxic waste produced by terrestrial mining—in the deep ocean.
“This use of the deep sea is ramping up, as the thought is that there isn't much to destroy in the deep sea compared to losses associated with disposal on land,” said Levin.
Mining is just one of the activities threatening the deep ocean.
Industrial fishing also poses a threat as bottom trawlers increasingly send their nets farther down into the ocean—the mean depth of fishing activity has increased by 1,150 feet since 1950. Trawlers drag weighted nets along the seabed, effectively clear-cutting the ocean floor. About 20 percent of the ocean floor has already been trawled at least once. That matters because some fish in the deep live to be more than 100 years old, and corals live to more than 1,000 years.
Scientists are still just starting to discover the unique ecosystems of the deep ocean. “Given our substantial knowledge gaps, any future exploitation of deep-ocean resources must be balanced with lasting protection of habitats, biodiversity, and services,” Levin and her coauthors wrote in a Science policy forum article in May.