Effects of boundary hydraulics, dissolved oxygen, and dissolved organic carbon on growth and death dynamics of aerobic microbes in riverbed dune-induced hyporheic zones
Journal Article
·
· Science of the Total Environment
- Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Virginia Tech
- Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
Surface and groundwater interact in the hyporheic zone beneath and adjacent to rivers in the presence of a diverse microbial community. Heterotrophic bacteria mediate a range of environmentally important reactions, yet few studies have quantified bacterial growth and death dynamics in the hyporheic zone, and none have systematically analyzed their response to variations in hydraulic or chemical conditions. Here we used MODFLOW and SEAM3D to simulate hydraulics; dissolved oxygen (DO) and dissolved organic carbon (DOC) transport; and aerobic microbial metabolism, growth, and death in hyporheic zones induced by riverbed dunes. We ran simulations both with and without growth/death processes, and varied hydraulic parameters and DO/DOC boundary concentrations. Microbial biomass reached steady state (t = 3 days) in every simulation, at which time there was greater biomass and DOC biodegradation rates in the hyporheic flowcell (300% and 85% higher for the base case, respectively) when accounting for microbial growth dynamics. This occurred as microbial biomass tailored its spatial distribution to the availability of DO and DOC, demonstrating the importance of simulating growth/death processes. Biomass generally increased with hyporheic flow cell area as upwelling groundwater decreased. When varying surface water DO and DOC source concentrations relative to the base case, the greatest effect on biomass occurred when increasing DOC and decreasing DO. We determined minimum DO and DOC steady-state concentrations required for microbial growth, but the minimums were not absolute or related by stoichiometry. Increasing DOC created a smaller area of microbes with higher concentrations relative to the base case. Increasing DO slightly increased the area occupied by microbes while keeping the total biomass nearly constant. Overall, microbial growth and death dynamics depend on DO and DOC availability in the hyporheic zone, which is dependent on DOC/DO boundary concentrations and hyporheic flow paths, and in turn the hydraulic interaction between surface water and groundwater.
- Research Organization:
- Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- SC0021402
- OSTI ID:
- 2283645
- Alternate ID(s):
- OSTI ID: 2369052
- Journal Information:
- Science of the Total Environment, Journal Name: Science of the Total Environment Vol. 906; ISSN 0048-9697
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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