Research Background
A team led by Prof. Liu Yi from the Earth and Ocean Atmospheric Sciences (EOAS) Thrust at the HKUST (GZ), in collaboration with Prof. Gan Jianping from the HKUST and Prof. Jiao Jiujiu from the University of Hong Kong, published an article titled "Carbonate weathering enhances nitrogen assimilatory uptake in rivers globally" in the prestigious Earth Sciences journal, Nature Geoscience on April 28. This study reveals for the first time the mechanism by which carbonate weathering enhances nitrogen (N) assimilation in rivers by regulating dissolved inorganic carbon (DIC). This finding not only deepens the understanding of how geological background influences the C-N coupling cycle in rivers and other biogeochemical processes but also provides a new perspective for global river ecological governance and carbon neutrality goals..
It is generally believed that the supply of N and phosphorus (P) in river ecosystems are key factors limiting N assimilation in scientific communities. However, this study, through field observations and incubation experiments in the Pearl River Basin and Indonesia, as well as global data analysis, first confirms the core role of DIC in the N assimilation. The study shows that under equivalent solar radiation and temperature, rivers in regions with high carbonate rock content exhibit higher nutrient uptake efficiency and phytoplankton production efficiency due to the high concentrations of DIC formed by carbonate weathering compared to regions with lower carbonate rock content. This finding challenges the traditional "N-P limitation theory" and reveals a new mechanism of 'N-P-C' limitation on the C-N coupling cycle in rivers.
Results
Through global data analysis, the study confirms a positive correlation between the distribution of carbonate rocks and organic N concentrations in rivers, showing that incorporating DIC as a limiting factor significantly enhances the explanatory power of solar radiation and temperature on global dissolved organic N. This discovery reveals the "inherent shaping" role of geological background in river biogeochemical cycles and emphasizes the ecological response mechanisms of river biogeochemical cycles to geological background.
Figure 1: Conceptual model of N assimilation enhanced by carbonate weathering.
For more detaileds, please refer to Qi, H., Liu, Y., Wang, H., Kuang, X., Putra, A. N., Jiao, J. J., & Gan, J. (2025). Carbonate weathering enhances nitrogen assimilatory uptake in rivers globally. Nature Geoscience, 18(5), 402-409. https://doi.org/10.1038/s41561-025-01680-w.