Scientists at the Georgia Institute of Technology have discovered that diatoms, microscopic algae found on the ocean floor, can rapidly alter ocean chemistry through their silica-based skeletons. The study, published in Science Advances, reveals that these structures transform into clay minerals in as little as 40 days—a process previously thought to take hundreds or thousands of years.
“We’ve known that reverse weathering shapes ocean chemistry, but no one expected that it happens this fast,” said Yuanzhi Tang, professor in the School of Earth and Atmospheric Sciences at Georgia Tech and senior author of the study. “This shows that the molecular-scale reactions can reverberate all the way up to influence ocean carbon cycling and, ultimately, climate.”
Diatoms play a key role while alive by absorbing carbon dioxide and releasing oxygen through photosynthesis. After they die, most of their silica skeleton dissolves back into seawater. However, some undergo reverse weathering—a chemical process that forms new clay minerals containing trace metals while releasing sequestered carbon back into the atmosphere. This links silicon, carbon, and metal cycles in the ocean.
The research team simulated seafloor conditions using a custom-built reactor with separate chambers for diatom silica and iron/aluminum minerals. A thin membrane allowed dissolved elements to interact without mixing solids. Through advanced microscopy and spectroscopy techniques, they observed diatom shells transforming fully into iron-rich clays within 40 days.
“It was remarkable to see how quickly diatom skeletons could turn into completely new minerals and to decipher the mechanisms behind this process,” said Simin Zhao, first author and former Ph.D. student in Tang’s lab. “These transformations are small in size but are enormous in their implications for global elemental cycles and climate.”
Jeffrey Krause, co-author from Dauphin Island Sea Lab and University of South Alabama added: “Diatoms are central to marine ecosystems and the global carbon pump. We already knew their importance to ocean processes while living. Now we know that even after they die, diatoms’ remains continue to shape ocean chemistry in ways that affect carbon and nutrient cycling. That’s a game-changer for how we think about these processes.”
The findings help explain why more silica enters oceans than is buried on the seafloor—much is converted rapidly into new minerals rather than accumulating as sediment. The results also provide important data for climate modelers studying how oceans regulate atmospheric carbon dioxide levels (https://doi.org/10.1126/sciadv.adt3374).
“This study changes how scientists think about the seafloor, not as a passive burial ground, but as a dynamic chemical engine,” Tang said.
Tang emphasized that understanding mineral formation at an atomic level reveals how small-scale processes can impact planetary systems: “By understanding how minerals form and exchange elements at the atomic level, we can see how the ocean shapes global cycles of carbon, silicon, and metals. Even molecular-scale reactions within hair-sized organisms can ripple outward to shape planet-level dynamics.”
The researchers plan further studies on environmental factors affecting these transformations using samples from various marine environments.
“It’s easy to overlook what’s happening quietly in marine sediments,” Tang concluded. “But these subtle mineral reactions are part of the machinery that regulates Earth’s climate, and they’re faster and more beautiful than we ever imagined.”
The research received funding from the National Science Foundation (OCE-1559087; OCE-1558957).
