Transition of carbon-nitrogen coupling under different anthropogenic disturbances in subtropical small mountainous rivers

Li Chin Lee, Gabriele Weigelhofer, Thomas Hein, Shin Chien Chan, Ying San Liou, Chien Sen Liao, Fuh Kwo Shiah, Yu Lin Yu, Tsung Yu Lee, Jr Chuan Huang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


The commonly observed inverse relationship between dissolved organic carbon (DOC) and nitrate (NO3) concentrations in aquatic systems can be explained by stoichiometric and thermodynamic principles regulating microbial assimilation and dissimilation processes. However, the interactive effects of human activities and dissolved oxygen (DO) on the DOC and DIN (dissolved inorganic nitrogen, mainly composed of NO3-N and NH4+-N) relations are not well identified, particularly in subtropical small mountainous rivers (SMRs). Here, we investigated the exports and relations of DOC-DIN in 42 Taiwan SMRs under different anthropogenic disturbances. Results showed that the island-wide mean concentrations of the three solutes in streams are generally low, yet the abundant rainfall and persistent supply contrarily lead to disproportional high DOC and DIN yields. The inverse DOC-NO3-N relation does not appear under well‑oxygenated conditions, regardless of low or high human disturbance. However, a significant inverse relationship between DOC-NO3-N would emerge in highly-disturbed watersheds under low-oxygenated conditions (mean annual DO <6.5 mg L−1), where excess N accumulates as NH4+-N rather than NO3-N. The controlling mechanism of DOC-DIN relations would shift from energetic constraints to redox constraints in low-oxygenated conditions. Although riverine concentrations of DOC, NO3-N, and NH4+-N could be elevated by human activities, the transition of DOC-DIN relation pattern is directly linked to DO availability. Understanding the mechanism that drives C–N coupling is critical for assessing the ecosystem function in the delivery and retention of DOC and DIN in aquatic ecosystems.

Original languageEnglish
Article number162017
JournalScience of the Total Environment
Publication statusPublished - 2023 Apr 20


  • Dissolved inorganic nitrogen (DIN)
  • Dissolved organic carbon (DOC)
  • Ecological stoichiometry
  • Small mountainous rivers (SMRs)
  • Taiwan
  • Thermodynamic constraint

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution


Dive into the research topics of 'Transition of carbon-nitrogen coupling under different anthropogenic disturbances in subtropical small mountainous rivers'. Together they form a unique fingerprint.

Cite this