If you know what diatoms are, it's probably for their beauty. These single-celled algae found on the ocean floor have ornate glassy shells that shine like jewels under the microscope.
Their pristine geometry has inspired art, but diatoms also play a key role in ocean chemistry and ecology. While they are alive, these algae contribute to the climate by drawing down carbon dioxide from the atmosphere and releasing oxygen through photosynthesis, while fueling marine food webs.
Now, a team led by Georgia Tech scientists has revealed that diatoms leave a chemical fingerprint long after they die, playing an even more dynamic role in regulating Earth's climate than once thought.
In a study published in Science Advances, the researchers found that diatoms' intricate, silica-based skeletons transform into clay minerals in as little as 40 days. Until the 1990s, scientists believed that this enigmatic process took hundreds to thousands of years. Recent studies whittled it down to single-digit 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 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."
From Glass to Clay
When a diatom dies, most of its silica skeleton dissolves on the seafloor, returning silica to the seawater. The rest can undergo reverse weathering - a process that transforms the silica into new clay minerals containing trace metals, while turning naturally sequestered carbon back to the atmosphere as sediments react with seawater. This recycling links silicon, carbon, and trace-metal cycles, influencing ocean chemistry and stabilizing the planet's climate over time.
Tang and her team set out to uncover how, and how quickly, reverse weathering happens. Using a custom-built, two-chamber reactor, they recreated seafloor conditions in the lab. One chamber held diatom silica, while the other contained iron and aluminum minerals. A thin membrane allowed dissolved elements to mix while keeping the solids separate.
Using advanced microscopy, spectroscopy, and chemical analyses, the researchers tracked the full transformation from the dissolution of diatom shells to the formation of new clays.
The results were striking. Within just 40 days, the diatom silica became iron-rich clay minerals - the same minerals naturally found in marine sediments.
Tang noted that this rapid transformation means that reverse weathering isn't a slow background process, but rather an active part of the modern ocean's chemistry. It can control how much silica stays available for diatoms to grow, how much carbon dioxide is released or stored, and how trace metals and nutrients are recycled in marine ecosystems.
"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, the paper's first author and a 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," she added.
The results suggest that the influence of reverse weathering on the coupled silicon-carbon cycles may also respond on far shorter timescales, making the ocean's chemistry more dynamic - and potentially more sensitive to modern environmental changes.
"Diatoms are central to marine ecosystems and the global carbon pump," said Jeffrey Krause, co-author and oceanographer at the Dauphin Island Sea Lab and the 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."
The discovery also helps solve a long-standing mystery about what happens to silica in the ocean, Tang says.
Scientists have long known that more silica enters the ocean than gets buried on the seafloor. The findings suggest that rapid reverse weathering transforms much of it into new minerals instead, keeping ocean chemistry in balance.
From Atoms to Earth Systems and Beyond
The findings offer new data for climate modelers studying how the ocean regulates atmospheric carbon. The research also lays the groundwork for improving models of ocean alkalinity and coastal acidification - key tools for predicting how the planet will respond 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.
Tang sees the study as a powerful reminder of why basic research matters. "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."
The team's next steps are to explore how environmental factors such as water chemistry influence these transformations. They also plan to use samples from coastal and deep-sea sites to see how these lab discoveries translate to natural environments.
"It's easy to overlook what's happening quietly in marine sediments," Tang said. "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."
Citation: Simin Zhao et al., Rapid transformation of biogenic silica to authigenic clay: Mechanisms and geochemical constraints. Sci. Adv. 11, eadt3374 (2025).
DOI: https://doi.org/10.1126/sciadv.adt3374
Funding: National Science Foundation (OCE-1559087; OCE-1558957)
