Ocean uptake of CO$_2$ will help moderate future climate change, but the subsequent hydrolysis of CO$_2$ in seawater increases the hydrogen ion concentration. In addition, dissolved CO$_2$ itself can influence the physiology and biochemistry of marine organisms by decreased pH of body fluid during exposure. To mitigate the impact of the future atmospheric CO$_2$ increase, CO$_2$ sequestration into sub-seabed structures such as gas reservoir or saline aquifer has been proposed recently. Here we proposed a preliminary framework for the risk assessment of CO$_2$ leakage during transportation, injection and/or storage process in Korea. Our framework has three compartments: (1) the assessment of leakage probability during operational process and from the storage site, (2) the prediction of the fate of released CO$_2$ and (3) the assessment of risk posed to the marine organisms during exposure to elevated CO$_2$ concentration in seawater. For the effect assessment of dissolved CO$_2$ in seawater, we have tried to develop 'no-effect level of CO$_2$' for most of marine organisms during acute and chronic exposure period. So we have conducted a series of bioassay using representative marine species including bioluminescent bacteria, harpacticoid copepod, benthic amphipod, fish and sea urchin.