Bacterial community responses during a possible CO2 leaking from sub-seabed storage in marine polluted sediments

•Elements release allowed the use of energy by bacterial community to grow and multiply.•Bacterial community composition and diversity were impacted under CO2 concentrations.•Respiring activity may be used as a bioindicator in evaluation of a possible CO2 leakage.

Carbon capture and storage (CCS) is a viable option to reduce high concentrations of CO2 and mitigate their negative effects. This option has associated risks such as possible CO2 leakage from the storage sites. So far, negative effects deriving from a CO2 release have been reported for benthic macrofauna in both polluted and nonpolluted sediments. However, bacterial communities has no considered. In this work, risk assessment was carried out in order to evaluate the possible effects in a contaminated area considering bacterial responses (total number of cells, respiring activity, changes in the bacterial community composition and diversity). Four microcosms were placed into an integrated CO2 injection system with a non-pressurized chamber to simulate four different pH treatments (pH control 7.8, 7, 6.5 and 6). Results showed an impact on bacterial communities because of the CO2 treatment. Changes in respiring activity, community composition groups and diversity were found. This study highlights the use of respiring bacteria activity not only as bioindicator for environmental risk assessment and monitoring purposes but also as a bioindicador during a CO2 leakage event or CO2 enrichment process among all the responses studied.

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