The response of the benthic microbial community to a controlled sub-seabed CO2 leak was assessed using quantitative PCR measurements of benthic bacterial, archaeal and cyanobacteria/chloroplast 16S rRNA genes. Similarly, the impact of CO2 release on the abundance of benthic bacterial and archaeal ammonia amoA genes and transcripts, and also to the abundance of nitrite oxidizer (nirS) and anammox hydrazine oxidoreductase (hzo) genes and transcripts. Samples were taken from four zones (epicentre (zone 1); 25m distant (zone 2), 75m distant (zone 3) and 450m distant (zone 4)) during 6 time points (7 days before CO2 exposure, after 14 and 36 days of CO2 release, and 6, 20 and 90 days after the CO2 release had ended). Changes to the active community of microphytobenthos and bacteria were also assessed before, during and after CO2 release using Denaturing Gradient Gel Electrophoresis of cyanobacteria/chloroplast 16S rRNA. Changes to the composition of the active bacterial community was assessed first using Terminal Restriction Fragment Length Polymorphism (T-RFLP) of bacterial 16S rRNA. In depth comparisons of possible changes to the active bacterial community at zone 1 and 4 before, during and immediately after the CO2 release was performed using 16S rRNA 454 pyrosequencing. This dataset was created by Plymouth Marine Laboratory (PML) under the program QICS (Quantifying and monitoring environmental impacts of geological carbon storage) which was funded by the Natural Environment Research Council (NERC), with support from the Scottish Government. The results are contained in three text files. QICS project website: www.bgs.ac.uk/qics/home.html. Tait et al. (2015) Rapid response of the active microbial community to CO2 exposure from a controlled sub-seabed CO2 leak in Ardmucknish Bay (Oban, Scotland). IJGGC DOI: 10.1016/ijggc.2014.11.021. Watanabe et al. (2015) Ammonia oxidation activity of microorganisms in surface sediment to a controlled sub-seabed release of CO2. IJGGC DOI: 10.1016/j.ijggc.2014.11.013.
