2026-09-15 パシフィック・ノースウェスト国立研究所（PNNL）
A worldwide study of sediment and surface-water dissolved organic matter (DOM) showed that unknown molecules (dark matter) had higher compositional diversity than identifiable molecules (known matter). This effect on diversity was linked to dissolved organic carbon concentrations, and the effect was distinct between surface-water and sediment DOM. These outcomes highlight the important role of unannotated DOM, motivating a need to further characterize the role of DOM in river corridor biogeochemical cycling and overall ecosystem functioning. (Image from Cui et al. 2026)
＜関連情報＞
- https://www.pnnl.gov/publications/hidden-molecules-influence-diversity-organic-matter
- https://www.sciencedirect.com/science/article/abs/pii/S0043135425017737
河川溶存有機物のダークマターとその分子化学多様性における役割の解明 Unveiling the dark matter of riverine dissolved organic matter and its role in molecular chemodiversity
Yifan Cui, Shuailong Wen, James C. Stegen, Ang Hu, Jianjun Wang
Water Research Available online: 29 October 2025
DOI:https://doi.org/10.1016/j.watres.2025.124870
Highlights
- DOM dark matter showed higher relative intensity in river sediments than waters.
- Dark matter had lower molecular diversity but higher compositional dissimilarity than known matter.
- DOC drove molecular weight, diversity, and composition of dark matter.
- DOC mediated dark matter’s effects on DOM chemodiversity.
- Dark matter neglect in sediment DOM overestimated DOC’s regulatory role in chemodiversity.
Abstract
Chemodiversity of riverine dissolved organic matter (DOM) plays a crucial role in global elemental cycles and ecosystem function. However, DOM “dark matter”—molecules without assigned specific formulae—remain unexplored in the interpretation of chemodiversity. Here, we systematically investigated the characteristics and drivers of dark matter and its impacts on DOM chemodiversity using 551 river water and sediment samples. Compared to known matter with specific formulae, dark matter exhibited lower molecular weight and diversity, but higher compositional dissimilarity, with dissolved organic carbon (DOC) as the primary driver. Including dark matter into chemodiversity analysis changed mass, diversity, and compositional dissimilarity of DOM from –10.1 to –0.04 %, –0.7 to 4.9 %, and 0.4 to 28.8 % in waters, and from –17.5 to 5.7 %, –10.5 to 19.2 %, and –22.3 to 33.1 % in sediments, respectively. DOC mediated these ecosystem-dependent effects: lower DOC amplified the effects on chemodiversity in waters, whereas in sediments, the effects shifted from negative to positive with changing DOC. Furthermore, ignoring dark matter would overestimate the regulatory role of DOC on sediment DOM chemodiversity. Collectively, our findings clarify the influence of dark matter on DOM chemodiversity assessments across environmental gradients, improving understanding of riverine DOM and refining its analytical framework.
