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Recent research indicates that the waste produced by some of the planet’s tiniest creatures may play a role in mitigating greenhouse gas emissions. Scientists have discovered an innovative technique involving clay dust that enhances zooplankton’s ability to capture atmospheric carbon dioxide. This process, while not yet ready for ocean application, is thoroughly explained in a study published on December 10 in Scientific Reports, which will also be presented at the annual American Geophysical Union conference.
Phytoplankton Feeding the Zooplankton
The proposed technique builds upon the vital role of phytoplankton—microscopic plants that engage in photosynthesis and remove approximately 150 billion tons of carbon dioxide from the atmosphere annually. These organisms convert CO2 into organic carbon particles essential for their growth.
Upon the death of phytoplankton, much of the captured carbon may be released back into the atmosphere as marine bacteria decompose the remains. Here enters the zooplankton, which can help preserve this crucial carbon.
Sticky Balls
In the recent study, researchers conducted experiments using water samples from the Gulf of Maine taken during a phytoplankton bloom in 2023. When clay dust was introduced to the samples, it adhered to the organic carbon released by the phytoplankton, encouraging the growth of a glue-like substance produced by marine bacteria. This interaction allowed for the formation of small, sticky aggregations known as flocs.
The research team found that zooplankton consumed these flocs voraciously. Once digested, the clay particles contained within the zooplankton’s waste settle to the ocean floor, effectively sequestering the carbon for extended periods. Additionally, undigested flocs can also descend deeper, growing larger by collecting more organic matter on their journey.
The research highlights the potential for clay dust to enhance carbon capture by creating sticky carbon-rich particles that zooplankton consume or that sink into deeper waters. This innovative method could significantly change carbon storage dynamics in our oceans.
In the controlled experiments, clay dust effectively captured up to 50% of the carbon released by dying phytoplankton, preventing it from returning to the atmosphere. The introduction of clay also led to an increase in organic particles capable of sequestering carbon, while at the same time reducing the populations of bacteria responsible for recycling carbon dioxide back into the atmosphere.
Marine Snow
Applying clay to the surface waters enhances a natural process known as the biological pump, which allows carbon to be sequestered in the ocean.
“Typically, only a small fraction of the carbon collected at the surface reaches the deep ocean for long-term storage. Our method enhances the biological pump’s efficiency,” explained Mukul Sharma, a planetary scientist at Dartmouth College and co-author of the study. “We aim to leverage the ocean’s biology to permanently trap carbon dioxide, sending these tiny pods down through the marine food chain and into the deep ocean.”
[Related: Sunken whale carcasses create entire marine cities on the ocean floor.]
Sharma also noted that the floc particles generated in the study become a crucial element of marine snow, a constant flux of organic matter that descends from the surface layers to nourish the deeper ocean environments.
“This innovation generates marine snow that can rapidly sequester carbon by deliberately binding it with clay minerals,” Sharma added.
Every Zooplankton Everywhere All at Once
Zooplankton contribute to expediting marine snow formation by virtue of their daily movements. During the diel vertical migration, these creatures venture from the depths to feed in nutrient-rich surface waters, akin to an entire community traveling considerable distances for a meal.
“Zooplankton are extraordinary eaters and excreters,” Sharma remarked. “When you examine their excrement, you can still find remnants of phytoplankton that were not fully digested.”
The clay-carbon flocs created in these experiments mix seamlessly with the usual diet of zooplankton. In the daylight, the flocs are carried back down into the depths as the zooplankton descend, where they are disposed of as feces, thus accelerating the carbon’s journey to lower layers—a process known as active transport.
“The zooplankton produce fecal pellets infused with clay that sink more quickly,” Sharma explained. “These organisms show no distinction between clay and phytoplankton; they consume it all. Consequently, this process enables significant carbon burial at greater depths.”
[Related: Sorry, zooplankton don’t want to eat your poop.]
‘We’re at the Beginning’
Future research will involve field tests where clay will be sprayed over phytoplankton blooms near Southern California, utilizing crop-dusting aircraft. Researchers plan to remain closely monitored with sensors at various depths to study how different zooplankton species interact with the clay-carbon flocs. This will assist in identifying optimal conditions for implementing this method and gauge the potential carbon sequestration in the deep ocean.
“Identifying suitable ocean conditions is crucial; indiscriminate dumping of clay is not an option,” Sharma emphasized. “Understanding the efficiency of our approach across different depths will help determine the best locations to initiate this project. At this point, we are just beginning our exploration.”
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