A new study led by researchers at the Georgia Institute of Technology has found that diatoms, single-celled algae known for their intricate glass-like shells, have a more immediate and dynamic impact on ocean chemistry than previously understood. The findings, published in Science Advances, indicate that after death, diatom skeletons can transform into clay minerals in as little as 40 days—a process scientists once thought took centuries or longer.
“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 an important role while alive by absorbing carbon dioxide from the atmosphere and supporting marine food webs through photosynthesis. After they die, most of their silica-based skeletons dissolve on the seafloor. However, some undergo a process called reverse weathering—transforming into new clay minerals containing trace metals and releasing previously stored carbon back into the atmosphere as sediments interact with seawater. This cycle links silicon, carbon, and trace metals in ways that affect long-term ocean chemistry.
The research team recreated seafloor conditions using a custom-built two-chamber reactor to observe how quickly these transformations occur. One chamber contained diatom silica; the other held iron and aluminum minerals. A thin membrane allowed dissolved elements to mix without letting solids come into contact.
Advanced microscopy and chemical analysis showed that within 40 days, diatom silica had become iron-rich clay minerals similar to those found naturally in marine sediments.
“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 of the paper 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.”
The results suggest that changes in reverse weathering—and its effect on coupled silicon-carbon cycles—may happen over much shorter timescales than previously believed. This makes ocean chemistry more dynamic and potentially more responsive to modern environmental changes.
“Diatoms are central to marine ecosystems and the global carbon pump,” said Jeffrey Krause, co-author from Dauphin Island Sea Lab and University of South Alabama. “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.”
Tang added that this discovery helps explain why not all silica entering oceans ends up buried on the seafloor: rapid reverse weathering converts much of it into new minerals instead.
The study provides valuable data for climate modelers who analyze how oceans regulate atmospheric carbon levels. It also lays groundwork for improving models related to ocean alkalinity and coastal acidification—both important for predicting responses to climate change.
“This study changes how scientists think about the seafloor, not as a passive burial ground, but as a dynamic chemical engine,” Tang said.
She emphasized broader significance: “This is where chemistry meets Earth systems,” she said. “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.”
Future work will examine how different environmental factors influence these mineral transformations using samples from both coastal regions and deep-sea sites.
“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 was funded by grants from the National Science Foundation (OCE-1559087; OCE-1558957). The full article is available via DOI: https://doi.org/10.1126/sciadv.adt3374
