Kinetic bottlenecks to chemical exchange rates for deep-sea animals – Part 2: Carbon Dioxide

[摘要] Increased ocean acidification from fossil fuel CO₂ invasion, fromtemperature-driven changes in respiration, and from possible leakage fromsub-seabed geologic CO₂ disposal has aroused concern over the impacts ofelevated CO₂ concentrations on marine life. Discussion of these impactshas so far focused only on changes in the oceanic bulk fluid properties(ΔpH, Δ[∑ CO₂], etc.) as the critical variable andwith a major focus on carbonate shell formation. Here we describe the rateproblem for animals that must export CO₂ at about the same rate at whichO₂ is consumed. We analyse the basic properties controlling CO₂export within the diffusive boundary layer around marine animals in an oceanchanging in temperature (T) and CO₂ concentration in order to comparethe challenges posed by O₂ uptake under stress with the equivalentproblem of CO₂ expulsion. The problem is more complex than that for anon-reactive gas, since with CO₂ the influence of the seawater carbonateacid-base system needs to be considered. These reactions significantlyfacilitate CO₂ efflux compared to O₂ intake at equal temperature,pressure and fluid flow rate under typical oceanic concentrations. The effectof these reactions can be described by an enhancement factor, similar to thatwidely used for CO₂ invasion at the sea surface. While organisms do needto actively regulate flow over their surface to thin the boundary layer totake up enough O₂, this seems to be not necessary to facilitate CO₂efflux. Instead, the main impacts of rising oceanic CO₂ will most likelybe those associated with classical ocean acidification science. Regionally,as with O₂, the combination of T, P and pH/pCO₂ creates azone of maximum CO₂ stress at around 1000 m depth.

[学科分类] 地球化学与岩石