A new study published in Environmental Science & Technology unveils the first global-scale “chemogeography” of dissolved organic matter (DOM) — a breakthrough in understanding how the invisible chemistry of the ocean connects to the planet’s carbon cycle and climate. The research analyzed over 800 ocean samples spanning from the surface to nearly 6,000 meters deep across the Atlantic, Pacific, and Southern Oceans. Using ultrahigh-resolution mass spectrometry, the team discovered consistent patterns in how DOM molecular compositions change with geographic distance — a phenomenon known as distance–decay — revealing that the ocean’s vast molecular diversity becomes increasingly uniform at greater depths and higher latitudes.
This global “chemogeographical” map highlights that both stochastic and deterministic ecological processes—such as physical mixing and selective degradation—contribute to the homogenization of organic molecules, effectively creating what the authors describe as a “carbon homogenizer.” The study’s findings show that compositional turnover rates decline toward the deep ocean, signaling a shift from chemically diverse surface waters to more uniform, refractory molecular assemblages that dominate long-term carbon storage. By quantifying these large-scale molecular transitions, the researchers provide new evidence that the deep ocean acts as a stabilizing reservoir in Earth’s carbon cycle, buffering climate feedbacks over millennia.
By integrating ecological theory with marine chemistry, this study pioneers a new way of viewing ocean biogeochemistry through an ecological lens. Just as biodiversity studies track how species change across landscapes, chemogeography reveals how molecular “communities” evolve across space and depth. This conceptual leap deepens our understanding of how marine organic matter responds to environmental change — offering a critical foundation for predicting how global warming may reshape the chemistry, ecology, and climate-regulating functions of the world’s oceans.
Here is the abstract:
Dissolved organic matter (DOM) comprises a diverse mixture of organic molecules, playing a critical role in marine biogeochemistry and Earth’s climate. However, the ecological patterns and drivers of DOM composition at the global scale and their variation across compound classes remain unclear. Here we quantify the compositional turnover of over 800 DOM samples covering the surface waters to the deep across the global ocean, using distance–decay relationships based on an ultrahigh-resolution mass spectrometry data set. Molecular compositions become increasingly dissimilar to greater geographical distances in both horizontal and vertical dimensions. The observed turnover rates, consistent across biochemically labile and recalcitrant compound classes, progressively decrease toward the deep ocean and high latitudes, indicating a trend of chemohomogenization. The geographical distribution is jointly influenced by horizontal spatial distance, water depth, and physicochemical environments, which suggests that both stochastic and deterministic processes shape the DOM composition homogenization, effectively acting as a “carbon homogenizer”. This study unravels geographical patterns of DOM compositional turnover in the global ocean from an ecological perspective, deepening understanding of the forthcoming biogeochemical changes under global warming.
How to cite:
Wang J, et al. 2025 Toward the Chemogeography of Dissolved Organic Matter in the Global Ocean. Environ Sci Technol. DOI:10.1021/acs.est.5c02477. https://pubs.acs.org/doi/10.1021/acs.est.5c02477 [PDF download]
