Thu, Aug 05, 2021:On Demand
Background/Question/Methods
Hydraulic fracturing is a method of gas and oil extraction that involves injecting high-pressure liquids into the bedrock which causes a fracture and allows oil and gas to flow. The process of well installation and well use alters land use within watersheds: an average of nine acres of forested area per well pad is altered during well pad installation. The deforestation associated with unconventional oil and gas (UOG) development can alter the hydrological processes of nearby streams by increasing surface water runoff and altering physicochemical properties such as temperature. Stream biofilms are layers of microorganisms, such as bacteria and algae, that adhere to benthic surfaces. Biofilms are the base of the stream food web; they fix gases, recycle organic matter, and serve as a food source for other stream life including invertebrates and fish. Therefore, any stress in these communities will impact the entire ecosystem. This study aims to explore the effects of hydraulic fracturing on streams by examining the biodiversity of photosynthetic eukaryotes (algae) in biofilms. We collected biofilm samples from 26 streams in W.V. with varying levels of hydraulic fracturing within the watershed. Watersheds were classified as non-impacted, impacted, or highly impacted based on the number of well pads, acres of pipeline, and land use associated with UOG development. For each stream, water and sediment chemical and physical parameters (e.g. pH, temperature, dissolved ions, etc.) were recorded. The biofilm eukaryotic microbial community composition was analyzed by amplicon sequencing of the 18S rRNA gene.
Results/Conclusions Highly impacted sites had warmer water temperatures and higher proportion of eukaryotic algae in biofilm communities, potentially due to greater stream light availability from deforestation. Both water temperature and the proportion of eukaryotic algae in biofilm communities were positively correlated with the number of well pads and the area UOG development within a watershed. Algal community composition was less variable in the highly impacted sites, suggesting hydraulic fracturing activity may have a homogenizing effect on algal communities. There was greater relative abundance of two diatom groups (Amphora and Nitschia) in the impacted watersheds suggesting these organisms may be useful indicators of hydraulic fracturing impacts on streams. Our results suggest that UOG development associated land change may increase light availability to streams thus increasing the ambient temperature and the relative abundance of phototrophic organisms within biofilms. These changes in biofilm eukaryotic algae are likely to impact higher trophic levels and alter broader ecosystem function.
Results/Conclusions Highly impacted sites had warmer water temperatures and higher proportion of eukaryotic algae in biofilm communities, potentially due to greater stream light availability from deforestation. Both water temperature and the proportion of eukaryotic algae in biofilm communities were positively correlated with the number of well pads and the area UOG development within a watershed. Algal community composition was less variable in the highly impacted sites, suggesting hydraulic fracturing activity may have a homogenizing effect on algal communities. There was greater relative abundance of two diatom groups (Amphora and Nitschia) in the impacted watersheds suggesting these organisms may be useful indicators of hydraulic fracturing impacts on streams. Our results suggest that UOG development associated land change may increase light availability to streams thus increasing the ambient temperature and the relative abundance of phototrophic organisms within biofilms. These changes in biofilm eukaryotic algae are likely to impact higher trophic levels and alter broader ecosystem function.