Groundwater–surface water mixing shifts ecological assembly processes and stimulates organic carbon turnover

• Published in: Nature communications Vol. 7; no. 1; pp. 11237 - 12
• Main Authors: Stegen, James C., Fredrickson, James K., Wilkins, Michael J., Konopka, Allan E., Nelson, William C., Arntzen, Evan V., Chrisler, William B., Chu, Rosalie K., Danczak, Robert E., Fansler, Sarah J., Kennedy, David W., Resch, Charles T., Tfaily, Malak
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 07.04.2016; Nature Publishing Group; Nature Portfolio
• Subjects: 704/158/47; 704/158/855; 704/2151/241; Bacteria - classification; Bacteria - genetics; Bacteria - metabolism; Biodegradation, Environmental; biogeochemical hotspot; Biogeochemistry; Carbon; Carbon - chemistry; Carbon - metabolism; deterministic selection; DNA, Bacterial - genetics; ecological drift; ecological null model; Ecosystem; ENVIRONMENTAL SCIENCES; FTICR mass spectrometry; Groundwater - chemistry; Groundwater - microbiology; Hanford 300 Area; Humanities and Social Sciences; hyporheic zone; Microbial activity; Microbial Consortia - physiology; mixing model; multidisciplinary; Organic carbon; Organic compounds; phylogenetic beta-diversity; Prediction models; Rivers - chemistry; Rivers - microbiology; Science; Science (multidisciplinary); Sequence Analysis, DNA; subsurface biogeochemistry; subsurface microbiology; Surface water; Surface-groundwater relations; Washington; Water mixing; Water Movements; Water Pollutants, Chemical - metabolism; Washington
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms11237

Environmental transitions often result in resource mixtures that overcome limitations to microbial metabolism, resulting in biogeochemical hotspots and moments. Riverine systems, where groundwater mixes with surface water (the hyporheic zone), are spatially complex and temporally dynamic, making development of predictive models challenging. Spatial and temporal variations in hyporheic zone microbial communities are a key, but understudied, component of riverine biogeochemical function. Here, to investigate the coupling among groundwater–surface water mixing, microbial communities and biogeochemistry, we apply ecological theory, aqueous biogeochemistry, DNA sequencing and ultra-high-resolution organic carbon profiling to field samples collected across times and locations representing a broad range of mixing conditions. Our results indicate that groundwater–surface water mixing in the hyporheic zone stimulates heterotrophic respiration, alters organic carbon composition, causes ecological processes to shift from stochastic to deterministic and is associated with elevated abundances of microbial taxa that may degrade a broad suite of organic compounds. Groundwater-surface water mixing zones link critical ecosystem domains, but attendant microbe-biogeochemistry-hydrology interactions are poorly known. Here, the authors show that groundwater-surface water mixing stimulates respiration, alters carbon composition, and shifts the ecology from stochastic to deterministic.