Deep Sea Migrations: Earth's Hidden Climate Engine

A vast, nightly migration of trillions of tiny animals in the ocean's twilight zone is being highlighted by scientists as a critical climate helper. This daily event, known as diel vertical migration, involves an estimated 11 billion tons of biomass moving from the twilight zone, 200 to 1,000 meters below the surface, toward the ocean's surface.

As these organisms move to shallower waters to feed and then return to deeper areas to avoid predators, they transport significant amounts of carbon. This process is estimated to move as much as 6.6 billion tons of carbon into the deep ocean annually, a figure more than double the global emissions from cars. This carbon can remain stored for centuries.

This migration is essential for regulating the planet's climate and supports vital ocean food webs. Many species involved are prey for larger fish, which in turn support global fisheries and coastal economies. However, scientists warn that ocean warming, shifting food chains, and sea-ice loss could disrupt this migration.

While some marine protected areas exist, they often focus on the seafloor, not the entire water column where this migration occurs. This has led to calls for enhanced protections, including a proposed pause on expanded mesopelagic fishing until this deep-ocean region is better understood.