The first global-scale map is created for how dissolved organic matter (DOM) changes across the world’s oceans. Published on October 20, 2025, in Environmental Science & Technology, the study was led by Professor WANG Jianjun from the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences.

The researchers analyzed over 800 samples collected from 124 stations spanning surface waters to nearly 5,900 meters deep in the Atlantic, Pacific, and Southern Oceans. Using ultrahigh-resolution FT-ICR mass spectrometry, they found that the molecular "communities" of DOM change in predictable ways. DOM compositions become more different as water masses are farther apart horizontally or vertically. However, this rate of change slows significantly in the deep ocean and at high latitudes.

This pattern points to a process the authors call "chemohomogenization"—a convergence towards a shared pool of long-lasting molecules in the deep seas. This signal appears across both biochemically labile and recalcitrant compound classes and is driven by a combination of deterministic forces (e.g., temperature, salinity, and carbon availability) and stochastic processes (e.g., physical transport).

The study further reveals that environmental factors shape DOM in the upper 200 meters and mid-latitudes, while pure spatial effects—consistent with dispersal limitation and unmeasured factors—explain the variance at broader scales. 

“Warming will likely expand horizontal homogenization but weaken vertical mixing, especially at high latitudes,” said Professor WANG. “This could enhance the deep ocean's role as a carbon sink by preserving more organic molecules.” 

The findings provide a new theoretical framework of chemogeography to predict how ocean carbon storage will respond to climate change.