Methodology for Impact Assessment of Ocean CO2 Sequestration on Deep-sea Organisms

In order to assess the biological impact of ocean CO
₂
sequestration, we present a methodology to quantify impacts of elevated CO
₂
concentration on marine organisms using existing biological data and discuss required research work for the future. For a quantitative assessment of deep-sea CO
₂
injection (mid- depth type) impacts on marine organisms, we estimated No Observed Effect Concentration (NOEC) of CO
₂
for copepods. Our preliminary analysis indicated that the NOECco
₂
for copepods including deep-sea species is ≈ Δ3,000 ppm. However, further data are needed on acute, chronic and ecosystem impacts for applying reduced Assessment Factor (AF) which is essential for reliable estimation of Predicted No Effect Concentration (PNECco
₂
). For an acute impact assessment, careful consideration on differences in sensitivities to CO
₂
between shallow and deep- sea species is required. For the purpose of accurate chronic impact assessment, long-term experiments on sub-lethal impacts are required. However, ecosystem impacts would be difficult to predict based only on laboratory experiments and field experiments are necessary for confirming expected consequences from laboratory experiments and for lessening the uncertainties of extrapolation.