Impacts of Elevated CO2 Levels on the Soil Bacterial Community in a Natural CO2-Enhanced Oil Recovery Area

Jing Ma,Zhanbin Luo,Run Chen,Shaoliang Zhang,Qianlin Zhu,Fu Chen

doi:10.3390/d11050077

Abstract

Knowledge of the interactions among different microorganisms is important to understand how ecological function transformation is affected by elevated CO2 levels in CO2-enhanced oil recovery (CO2-EOR) sites. Molecular ecological networks were established to reveal the interactions among different microbes of the soil bacterial community with the high-throughput sequencing data of 16S rRNA genes. The results showed that these networks are a powerful tool to identify and explain the interactions and keystone species in the communities under elevated CO2 pressure. The structures of networks under different CO2 leakage concentrations were different as a result of the networks’ topology properties, such as node numbers, topological roles of individual nodes, and network hubs. These indicators imply that the interactions among different groups were obviously changed. Moreover, changes in the network structure were significantly correlated with soil pH value, which might suggest that the large CO2 leakage affected the soil ecosystem functions by changing the network interactions. Additionally, the key microbial populations such as Bacteroidetes and Proteobacteria were distinguished based on network topology to reveal community structure and ecosystem functioning. The work developed in this study could help microbiologists to address some research questions that could not be approached previously, and, hence, might represent a new area of research for microbial ecology.

Highlights

Global climate change, mainly caused by the anthropogenic CO2 emissions from the utilization of fossil fuels, has become a critical challenge [1]
The results indicate that the network interactions for some microbial groups become more complicated under higher CO2 concentration, which is consistent with our previous studies showing that microbial community structures were significantly changed by higher CO2 concentration [46]
This study demonstrated that the network interactions for most of the microbial groups became less complex under higher CO2 concentration

Summary

Introduction

Mainly caused by the anthropogenic CO2 emissions from the utilization of fossil fuels, has become a critical challenge [1]. CO2 -enhanced oil recovery (CO2 -EOR), which involves using CO2 to enhance oil recovery or improve the recovery ratio of oil reservoirs, as a promising technology of CCUS, has been widely applied in oil recovery around the world [4]. In the Shengli Oilfield, Yanchang Oilfield, Jilin Oilfield, and Shenhua Group [5,6]. This technology could improve the recovery ratio of oil reservoirs with low cost and high recoverability, Diversity 2019, 11, 77; doi:10.3390/d11050077 www.mdpi.com/journal/diversity. Diversity 2019, 11, 77 there is still a risk of gas leakage during the CO2 -EOR process. More attention should be paid to the potential environmental consequences induced by any kind of CO2 leakage [9,10]

Results

Discussion

Conclusion