An international study has revealed that these microscopic ocean dwellers—copepods, krill, and salps—play a far more significant role in carbon sequestration than previously thought. Copepods account for 80% of the carbon that sinks into the depths, while krill contribute about 14%, and salps about 6%.
Scientists have named this process the “seasonal migration pump.” Unlike the well-understood sinking of organic particles, this mechanism works differently: during their winter dormancy at depths greater than 500 meters, zooplankton release carbon through respiration and decay without depleting nutrients at the surface. This allows ecosystems to continue thriving while the carbon remains locked away in the ocean depths.
“Zooplankton are the unsung heroes of the climate system. Their seasonal migrations create a massive, previously uncounted carbon flux,” noted Dr. Guang Yang from the Institute of Oceanology, Chinese Academy of Sciences.
However, climate change is already affecting this “pump.” Ocean warming is altering species distribution—krill populations are declining, copepods are becoming dominant, and their food sources are changing. This could radically alter the role of zooplankton in the global carbon cycle.
According to Professor Angus Atkinson from Plymouth Marine Laboratory, the data for the first time allows for an assessment of the scale of this hidden mechanism. Scientists are urging for this process to be included in climate models and for more attention to be paid to preserving oceanic ecosystems.
The Southern Ocean already absorbs up to 40% of human-caused CO₂, and a significant part of this process depends on these microscopic “migrants.” Therefore, protecting zooplankton and their habitat is becoming a vital part of global warming mitigation strategies.
It’s important to note that the Southern Ocean is defined as the southern portions of the Pacific, Atlantic, and Indian Oceans that surround Antarctica. Some scientists recognize it as a fifth ocean, though it lacks a clear northern boundary defined by islands and continents.
