TY - JOUR
T1 - Transition of carbon-nitrogen coupling under different anthropogenic disturbances in subtropical small mountainous rivers
AU - Lee, Li Chin
AU - Weigelhofer, Gabriele
AU - Hein, Thomas
AU - Chan, Shin Chien
AU - Liou, Ying San
AU - Liao, Chien Sen
AU - Shiah, Fuh Kwo
AU - Yu, Yu Lin
AU - Lee, Tsung Yu
AU - Huang, Jr Chuan
N1 - Funding Information:
This study was sponsored by Taiwan's Ministry of Education , Austria's Agency for Education and Internationalisation ( OeAD TW 08/2021 ), and Taiwan's National Science and Technology Council (NSTC 110-2116-M-002 -022 - MY3 , NSTC 111-2740-M-002 -004 ). Additional support was provided by the International Cooperative Doctoral Program for scholarship from Taiwan's Ministry of Education . The authors are thankful to the group members who assisted in the field sampling or lab work. We thank James Ho for proof-reading the manuscript and the reviewers for their constructive comments.
Funding Information:
This study was sponsored by Taiwan's Ministry of Education, Austria's Agency for Education and Internationalisation (OeAD TW 08/2021), and Taiwan's National Science and Technology Council (NSTC 110-2116-M-002 -022 -MY3, NSTC 111-2740-M-002 -004). Additional support was provided by the International Cooperative Doctoral Program for scholarship from Taiwan's Ministry of Education. The authors are thankful to the group members who assisted in the field sampling or lab work. We thank James Ho for proof-reading the manuscript and the reviewers for their constructive comments.
Publisher Copyright:
© 2023 Elsevier B.V.
PY - 2023/4/20
Y1 - 2023/4/20
N2 - 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.
AB - 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.
KW - Dissolved inorganic nitrogen (DIN)
KW - Dissolved organic carbon (DOC)
KW - Ecological stoichiometry
KW - Small mountainous rivers (SMRs)
KW - Taiwan
KW - Thermodynamic constraint
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U2 - 10.1016/j.scitotenv.2023.162017
DO - 10.1016/j.scitotenv.2023.162017
M3 - Article
C2 - 36739020
AN - SCOPUS:85147604701
SN - 0048-9697
VL - 870
JO - Science of the Total Environment
JF - Science of the Total Environment
M1 - 162017
ER -