Abstract
Production of unconventional oil and gas continues to rise, but the effects of high-density hydraulic fracturing (HF) activity near aquatic ecosystems are not fully understood. A commonly used biocide in HF, 2,2-dibromo-3-nitrilopropionamide (DBNPA), was studied in microcosms of HF-impacted vs. HF-unimpacted surface water streams to (1) compare the microbial community response, (2) investigate DBNPA degradation products based on past HF exposure, and (3) compare the microbial community response differences and similarities between the HF biocides DBNPA and glutaraldehyde. The microbial community responded to DBNPA differently in HF-impacted vs. HF-unimpacted microcosms in terms of 16S rRNA gene copies quantified, alpha and beta diversity, and differential abundance analyses of microbial community composition through time. The difference in microbial community changes affected degradation dynamics. HF-impacted microbial communities were more sensitive to DBNPA, causing the biocide and byproducts of the degradation to persist for longer than in HF-unimpacted microcosms. Seventeen DBNPA byproducts were detected, many of them not widely known as DBNPA byproducts. Many of the believed to be uncharacterized brominated byproducts detected may pose environmental and health impacts. Similar taxa were able to tolerate glutaraldehyde and DBNPA, however DBNPA was not as effective for microbial control as indicated by a smaller overall decrease of 16S rRNA gene copies/mL after exposure to the biocide and a more diverse set of taxa was able to tolerate it. These findings suggest that past HF activity in streams can affect the microbial community response to environmental perturbation such as the biocide DBNPA.
