Microscopic ‘eating and pooping machines’ called zooplankton reduce carbon in the coean.
The tiniest creatures in the ocean might play a massive role in reducing greenhouse gases. Zooplankton, microscopic marine animals often overlooked in discussions about climate change, could help trap significant amounts of carbon dioxide in the deep ocean. Scientists recently discovered that adding clay dust to ocean water could enhance the ability of zooplankton to capture carbon, turning it into feces that sinks to the ocean floor, storing the carbon for thousands of years.
This breakthrough, published in Scientific Reports on December 10 and presented at the American Geophysical Union’s annual conference, demonstrates how zooplankton reduce carbon and how it could become a vital tool in combating climate change.
The method starts with phytoplankton, microscopic plants that float near the ocean’s surface and remove about 150 billion tons of carbon dioxide annually through photosynthesis. Phytoplankton convert carbon dioxide into organic material, which serves as food for marine life. When phytoplankton die, much of their carbon is released back into the atmosphere as marine bacteria break them down.
Enter zooplankton. These tiny creatures feed on phytoplankton, but in their natural state, only a small fraction of the carbon they consume reaches the deep ocean. Scientists from Dartmouth College, led by planetary scientist Mukul Sharma, conducted experiments to improve this process.
By adding clay dust to water samples from the Gulf of Maine during a 2023 phytoplankton bloom, they found that clay particles combined with organic carbon to form sticky balls called flocs. These flocs were then consumed by zooplankton.
“Zooplankton are eating and pooping machines,” said Sharma. “Our experiments showed that they can’t distinguish between pure phytoplankton and clay-coated flocs, they just eat it all. And when they poop it out, it sinks faster and deeper.”
The process of moving carbon from the surface to the ocean depths is part of a natural system called the biological pump. Typically, only a small amount of carbon captured at the surface reaches the deep ocean. The study’s method boosts the efficiency of this pump by accelerating the creation of marine snow—a mix of organic matter, minerals, and detritus that constantly falls from the ocean’s surface to its depths.
Zooplankton reduce carbon by consuming the clay-carbon flocs. Their feces become dense and heavy, allowing them to sink rapidly. This quicker descent means carbon spends less time in shallower waters, where it could potentially return to the atmosphere. According to Sharma, this approach could bury carbon much faster and more effectively than natural processes alone.
Zooplankton’s daily movements further enhance the process. During diel vertical migration, zooplankton rise to the surface at night to feed and descend to deeper waters during the day. This natural behavior actively transports carbon to greater depths. By consuming clay-coated flocs at the surface and depositing feces as they migrate, zooplankton play a crucial role in sinking carbon deeper into the ocean, faster.
“Normally, it takes a long time for carbon to reach the depths where it can be stored for thousands of years,” Sharma explained. “But with clay-enhanced flocs, the sinking process happens much faster.”
In the lab, adding clay dust captured up to 50% of the carbon released by dead phytoplankton before it could return to the atmosphere. The clay particles also reduced the number of bacteria responsible for releasing carbon from decaying phytoplankton. By creating more sticky organic particles, the clay increased the amount of carbon that could be trapped and transported to the ocean floor.
Sharma and his team believe the method could become a game-changer for ocean-based carbon sequestration. “We’re not reinventing the wheel,” Sharma said. “We’re enhancing a natural process that already happens in the ocean.”
While the lab results are promising, the method is still in its early stages. Future field experiments will test how the process works in real-world conditions. The team plans to spray clay onto phytoplankton blooms off the coast of Southern California using crop-dusting airplanes. Sensors placed at various depths will monitor how different zooplankton species interact with the clay-carbon flocs and measure the efficiency of carbon transport to deeper waters.
“It’s important to find the right locations and conditions to implement this method,” Sharma cautioned. “We can’t just go around dumping clay everywhere. We need to understand the environmental impacts and ensure it’s safe and effective.”
While the concept of using zooplankton to reduce carbon holds great promise, there are challenges to address. For instance, the method relies on creating and distributing clay particles on a large scale, which could have unintended effects on marine ecosystems. Additionally, ensuring that the added clay doesn’t disrupt other ocean processes or harm marine life will be critical.
Despite these hurdles, the potential benefits are immense. By enhancing natural carbon capture and storage mechanisms, this approach could significantly contribute to global efforts to reduce greenhouse gases. It also underscores the importance of leveraging the ocean’s biology to tackle climate change.
The discovery highlights how seemingly small and overlooked creatures like zooplankton can play an outsized role in addressing global challenges. By harnessing their natural behaviors and combining them with innovative techniques like clay flocs, scientists are finding new ways to fight climate change.
As Sharma and his team continue their research, the hope is that these findings will lead to scalable solutions for reducing atmospheric carbon dioxide. While the road ahead involves careful study and testing, the concept of zooplankton reducing carbon could mark a significant step forward in the quest for sustainable climate solutions.
