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ARS Home » Plains Area » Lincoln, Nebraska » Agroecosystem Management Research » Research » Publications at this Location » Publication #215704
Title: Microbial Characterization of Nitrification in a Shallow, Nitrogen-Contaminated Aquifer, Cape Cod, Massachusetts and Detection of a Novel Cluster Associated with Nitrifying Betaproteobacteria

Author
item Miller, Daniel
item SMITH, RICHARD - US GEOLOGICAL SURVEY

Submitted to: Journal of Contaminant Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2008
Publication Date: 1/26/2009
Citation: Miller, D.N., Smith, R.L. 2009. Microbial Characterization of Nitrification in a Shallow, Nitrogen-Contaminated Aquifer, Cape Cod, Massachusetts and Detection of a Novel Cluster Associated with Nitrifying Betaproteobacteria. Journal of Contaminant Hydrology. 103(3-4):182-193.

Interpretive Summary: The conversion of ammonium to nitrate (nitrification) is a poorly understood process in aquifers. Subsurface cores from two sites in a sewage-contaminated aquifer were examined using microbial and molecular tools to characterize nitrifying organisms present within the sediments. The first site was located at the source, which was a sewage treatment plant that discharged treated effluent containing both oxygen and ammonium. The second was 2.5 km down-gradient from the plant and was within a narrow zone containing both oxygen and ammonium and contained nitrate, which is a product of nitrification. A low abundance of microorganisms (< 105 g-1) capable of nitrification were enumerated by culture-based methods. Potential nitrifying activity was also very low, requiring several weeks for nitrate to accumulate. Molecular analysis of aquifer DNA detected primarily nitrifiers of the Nitrosospira genus throughout the cores at the down-gradient site and a smaller proportion from the Nitrosomonas genus in deeper cores. Only a single Nitrosospira clone was detected beneath the sewage treatment discharge source. Numerous non-nitrifying Betaproteobacteria clones also were detected in the libraries, which also held a large proportion of artifacts (24% of sequences). We conclude that Nitrosospira dominate at the geochemically stable, down-gradient site, but are absent at the sewage treatment plant, which is a more variable subsurface environment.

Technical Abstract: : Groundwater nitrification is a poorly characterized process affecting the speciation and transport of nitrogen. Cores from two sites in a sewage-contaminated groundwater plume were examined for microbial and molecular evidence of nitrification processes. The first, located beneath a sewage effluent infiltration bed, received treated effluent containing O2 (>300 'M) and NH4+ (51-800 'M). The second was 2.5 km down-gradient within a narrow zone containing O2, NH4+, and NO3- (24, 37, and 260 'M, respectively). Ammonia- and nitrite-oxidizers were enumerated by the culture-based MPN method (1.8 to 350 g-1 and 33 to 35000 g-1, respectively). Potential nitrifying activity was very low, requiring several weeks for products to accumulate. Molecular analysis of aquifer DNA (nested PCR followed by cloning and 16S rDNA sequencing) detected primarily nitrifiers of the Nitrosospira genus throughout the cores at the down-gradient site and a smaller proportion from the Nitrosomonas genus in deeper cores. Only a single Nitrosospira clone was detected beneath the infiltration bed. Numerous non-nitrifying Betaproteobacteria clones also were detected in the libraries, which also held a large proportion of chimeras (24% of clones). We conclude that Nitrosospira dominate at the geochemically stable, down-gradient site, but are absent beneath the infiltration beds suggesting that Archeal nitrifiers may dominate where geochemical conditions are more variable.