Plankton play a vital role in carbon sequestration by absorbing carbon dioxide during photosynthesis and storing it in the depths of the ocean.

Plankton, which include both phytoplankton (plant-like organisms) and zooplankton (animal-like organisms), are microscopic creatures that float in the oceans and other bodies of water around the globe. They are essential components of the marine food web and significantly influence the global carbon cycle. During the process of photosynthesis, phytoplankton absorb carbon dioxide ($\text{CO}_2$), a greenhouse gas, from the atmosphere. This process transforms carbon dioxide into organic carbon, which phytoplankton utilize to construct their bodies and support their growth.

When plankton die or are consumed, they often sink to the deep ocean, carrying the carbon stored in their bodies with them. This phenomenon is referred to as the “biological pump.” Once in the deep ocean, this carbon can remain sequestered for hundreds to thousands of years, effectively removing it from the atmosphere and helping to mitigate the impacts of climate change. This natural form of carbon sequestration involves the long-term storage of carbon in various reservoirs, including plants, soils, geological formations, and the ocean itself.

Zooplankton also play a significant role in carbon sequestration. They feed on phytoplankton and other smaller zooplankton, incorporating the carbon from their prey into their own bodies. When zooplankton excrete waste or die, they can likewise sink to the ocean depths, transporting carbon with them. Certain species of zooplankton even engage in daily vertical migrations, feeding near the surface at night and descending to the depths during the day. This behavior can enhance the transport of carbon to the deep ocean.

However, the efficiency of the biological pump can be affected by various factors, including temperature, nutrient availability, and the specific types of plankton present. Changes in these conditions, driven by human activities or climate change, could potentially alter the effectiveness of plankton in sequestering carbon. Therefore, understanding the role of plankton in carbon sequestration is crucial not only for comprehending the global carbon cycle but also for predicting future climate change and developing strategies to mitigate its impacts.