In-stream metabolism and atmospheric carbon sequestration in a groundwater-fed karst stream
- Permanent Link:
- In-stream metabolism and atmospheric carbon sequestration in a groundwater-fed karst stream
- Series Title:
- Science of The Total Environment
- Pu, Junbing
Khadka, Mitra B.
Martin, Jonathan B.
- Publication Date:
- Subjects / Keywords:
- Carbon Sequestration ( local )
Dissolved Inorganic Carbon ( local )
In-Stream Metabolism ( local )
Aquatic Phototrophs ( local )
Diel Cycle ( local )
Karst System ( local )
- serial ( sobekcm )
- Atmospheric carbon sequestered in karst systems through dissolution of carbonate minerals is considered to have no net effect on long-term regional and global carbon budgets because precipitation of dissolved carbonate minerals emits CO2 back to the atmosphere. Even though recent studies have implied that rapid kinetics of carbonate dissolution coupled with the aquatic photosynthetic uptake of dissolve inorganic carbon (DIC) could facilitate a stable atmospheric C sink in karst rivers and streams, little is known about the magnitudes and long-term stability of this C sink. To assess in-stream biogeochemical processes and their role on stream C cycling, we measured diel cycles of water characteristics and chemical composition (temperature, pH, DO, SpC, DIC, Ca2 +, Î´13CDIC) in a groundwater-fed karst stream in southwest China. Our results show no diel variations at the groundwater discharge point (CK site) due to the absence of a sub-aquatic community (SAC). However, all hydrochemical parameters show significant diel cycle 1.3 km downstream (LY site). Diel variations in pH, DO, and Î´13CDIC were inversely related to diel changes in SpC, DIC, Ca2 + and pCO2. This result indicates that in-stream metabolism (photosynthesis and respiration) of SAC controls diel variations in stream water chemistry. Significant diel cycles of net ecosystem production (NEP) influences in-stream diel fluctuation of pH, DO, SIc, DIC, pCO2, Ca2 + and Î´13CDIC, with gross primary production (GPP) dominating in day and ecosystem respiration (ER) dominating at the night. Absence of in-stream metabolism at CK enhances CO2 degassing from stream to the atmosphere, which is estimated to be 3â€“ 5 times higher than at LY. We estimate the carbon sink through in-stream metabolism of SAC to be 73 t C kmâˆ’ 2 aâˆ’ 1, which is around half the rate of the oceanic biological pump. These results imply in-stream photosynthesis sequesters DIC originating from karst weathering and controls CO2 evasion.
- Original Version:
- Science of The Total Environment, Vol. 579 (2017-02-01).
- Source Institution:
- University of South Florida Library
- Holding Location:
- University of South Florida
- Rights Management:
- This object is protected by copyright, and is made available here for research and educational purposes. Permission to reuse, publish, or reproduce the object beyond the bounds of Fair Use or other exemptions to copyright law must be obtained from the copyright holder.
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