As global temperatures climb, a critical but often-overlooked component of our ecosystems is stepping into the spotlight: dissolved organic matter, or DOM. Found everywhere from river water to forest soils, DOM acts as a powerful mover of carbon, nutrients, and pollutants. A new review led by scientists from Kunming University of Science & Technology and international partners finds DOM to be both a buffer and a potential accelerator of climate change, playing a surprisingly complex role in the planet's environmental balance.
DOM is a diverse mixture of molecules released from decomposed plants, microorganisms, and even plastics. When temperatures rise and rainfall patterns shift, DOM's molecular structure changes, altering its environmental behavior and biological effects. According to the researchers, climate-induced changes are making DOM both a concern and a solution in the face of global warming.
"Our work highlights how global warming can push DOM to act as a carbon source, fueling greenhouse gas emissions, or as a carbon sink, capturing carbon for long periods," says lead author Dr. Jing Zhao. "What's more, these processes are shaped by climate-driven events like droughts, floods, wildfires, and permafrost thaw."
Key Findings
Global warming increases the aromaticity and carboxyl content of DOM, resulting in molecules with either higher stability or higher reactivity. The fate of these molecules helps determine whether DOM stores carbon or releases it to the atmosphere.
Changes in DOM affect how heavy metals, organic chemicals, and microplastics move and transform in the environment. New forms of DOM can enhance pollutant binding or, under some conditions, boost pollutant mobility and ecological risks.
Biological effects of DOM shift with its amount and structure. It can act as a nutrient and protective barrier for organisms, but excessive or chemically altered DOM may stress organisms by increasing reactive oxygen species or disrupting nutrient uptake.
DOM has a feedback relationship with climate change. Positive feedbacks, like increased CO2 and methane emissions from thawed permafrost, can intensify warming. Negative feedbacks, like long-term carbon storage in peatland DOM, can help offset emissions.
Broader Impacts for Public and Environment
The researchers found that DOM's double-edged role extends to pollutant regulation. Structural changes in DOM can both reduce and intensify the bioavailability of toxic substances such as mercury, pharmaceuticals, and microplastics. For instance, as drought and warming make DOM more aromatic, its ability to bind to pollutants often grows. However, these same changes may turn DOM from a protective shield into a vector for toxins, especially in increasingly polluted and plastic-contaminated waters.
Climate change also increases DOM's interaction with pollutants and living organisms. DOM can shield aquatic life from some stresses but can also increase pollutant uptake or trigger oxidative stress, depending on its concentration and molecular quality. Researchers urge caution in assuming all DOM changes benefit ecosystems.
Policy Implications and Future Directions
The authors call for governments and research institutions to enhance monitoring of DOM quality in the environment, including key chemical ratios and redox potential. They recommend establishing long-term observational networks to track DOM dynamics across ecosystems and guide climate change mitigation efforts.
"Dissolved organic matter is at the intersection of climate, water chemistry, and ecology," says Dr. Baoshan Xing, co-author and professor at the University of Massachusetts Amherst. "Understanding DOM's shifting impact is essential for protecting ecosystems and human well-being in a warming and increasingly complex world."
The study emphasizes the urgent need for interdisciplinary collaboration to improve analytical methods for DOM and to quantify its multiple environmental roles. Such efforts can help build robust policies aimed at climate adaptation, pollution reduction, and biodiversity conservation.
About the Study
