Modelling impacts and recovery in benthic communities exposed to localised high CO2

•We parameterised response of zoobenthos to low pH in marine biogeochemical/ecosystem model.•A comprehensive range of scenarios was examined revealing complexity of biotic response to low pH.•Precise benthic response is heavily dependent on model parameterisation.•Levels of impacts depend on both the duration of exposure and magnitude of the pH changes.•The impact of a leak is minimal when either the intensity or duration of perturbation is restricted.

Regulations pertaining to carbon dioxide capture with offshore storage (CCS) require an understanding of the potential localised environmental impacts and demonstrably suitable monitoring practices. This study uses a marine ecosystem model to examine a comprehensive range of hypothetical CO2 leakage scenarios, quantifying both impact and recovery time within the benthic system. Whilst significant mortalities and long recovery times were projected for the larger and longer term scenarios, shorter-term or low level exposures lead to reduced projected impacts. This suggests that efficient monitoring and leak mitigation strategies, coupled with appropriate selection of storage sites can effectively limit concerns regarding localised environmental impacts from CCS. The feedbacks and interactions between physiological and ecological responses simulated reveal that benthic responses to CO2 leakage could be complex. This type of modelling investigation can aid the understanding of impact potential, the role of benthic community recovery and inform the design of baseline and monitoring surveys.