Abstract
The China-Russia Crude Oil Pipeline (CRCOP) goes through 441 km permafrost soils in northeastern China. The bioremediation in case of oil spills is a major concern. So far, little is known about the indigenous bacteria inhabiting in the permafrost soils along the pipeline. A pilot 454 pyrosequencing analysis on the communities from four selected sites which possess high environment risk along the CRCOP is herein presented. The results reveal an immense bacterial diversity than previously anticipated. A total of 14448 OTUs with 84834 reads are identified, which could be assigned into 39 different phyla, and 223 families or 386 genera. Only five phyla sustain a mean OTU abundance more than 5% in all the samples, but they altogether account for 85.08% of total reads. Proteobacteria accounts for 41.65% of the total OTUs or 45% of the reads across all samples, and its proportion generally increases with soil depth, but OTUs numerically decline. Among Proteobacteria, the abundance of Beta-, Alpha-, Delta- and Gamma- subdivisions average to 38.7% (2331 OTUs), 37.5% (2257 OTUs), 10.35% (616 OTUs), and 6.21% (374 OTUs), respectively. Acidobacteria (esp. Acidobacteriaceae), Actinobacteria (esp. Intrasporangiaceae), Bacteroidetes (esp. Sphingobacteria and Flavobacteria) and Chloroflexi (esp. Anaerolineaceae) are also very common, accounting for 8.56% (1237 OTUs), 7.86% (1136 OTUs); 7.35% (1063 OTUs) and 8.27% (1195 OTUs) of total libraries, respectively. The ordination analysis indicates that bacteria communities in the upper active layer cluster together (similar), while bacterial consortia from the lower active layer and permafrost table scatter (less similar). The abundance of Rhodococcus (12 OTUs), Pseudomonas (71 OTUs) and Sphingomonas (87 OTUs) is even less (<0.01%). This effort to profile the background diversity may set the first stage for better evaluating the bacterial dynamics in response to accidental oil spills.
Highlights
The latitudinal permafrost in northeastern China (0.386106 km2) is mainly distributed in the northern part of the Da and Xiao Xing’an Mountains
This rarefaction curve indicates a large variation in the total number of OTUs in different samples, but the sequence coverage is still sufficient to capture the diversity of the bacterial communities, whereas the OTUs density is larger in the upper layer than the lower parts
The 454 pyrosequencing in this study enable us to quickly capture both high and low-abundance phylotypes in a single run, to circumvent potential bias that conventional fingerprints and cloning procedures might introduce, and provide a different picture which can greatly improve our knowledge about the indigenous bacteria in permafrost soils along the China-Russia Crude Oil Pipeline (CRCOP)
Summary
The latitudinal permafrost in northeastern China (0.386106 km2) is mainly distributed in the northern part of the Da and Xiao Xing’an Mountains. In 2010, the 953-km-long China-Russia Crude Oil Pipeline (CRCOP) was built with a modified conventional burial construction mode. It crosses 441 km of discontinuous permafrost and 465 km of deep (.1.5 m) seasonally frozen ground [2]. The CRCOP has been the focus of cold regions environment and engineering practices. For pipelines in cold regions, oil spills normally occur in the early commercial operation due to the differential frost-heave and thaw-settlement, and in the late stages because of cumulative corrosion and aging [3]. Oil spills can cause severe damage to cold ecosystems. The same levels of contamination can heavily damage the cold environments, as the cold ecosystems have adapted to harsh conditions in ways that make them more fragile [4]
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