How does rising atmospheric CO2 affect marine organisms?

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Arctic Copepods Getting Acidified ... Under Sea Ice ... in the Dark!
Lewis, C.N., Brown, K.A., Edwards, L.A., Cooper, G. and Findlay, H.S. 2013. Sensitivity to ocean acidification parallels natural pCO2 gradients experienced by Arctic copepods under winter sea ice. Proceedings of the National Academy of Sciences USA 110: 10.1073/pnas.131516210.

The authors write that "copepods comprise the dominant Arctic zooplankton; hence, their responses to OA [ocean acidification] have important implications for Arctic ecosystems, yet there is little data on their current under-ice winter ecology on which to base future monitoring or make predictions about climate-induced change."

What was done
To be able to make reasonable predictions about the subject, Lewis et al. examined "the natural distributions of the dominant Artic copepods found under winter sea ice in relation to the current seawater carbonate chemistry conditions and compared these with their short-term responses to future high CO2 conditions." This was done at the temporary Catlin Arctic Survey Ice Base (CIB) during late winter to early spring in 2011," where they say that "the zooplankton were dominated by adult calanoid copepods, comprising mainly the Arctic endemics Calanus glacialis and Calanus hyperboreus but also the smaller, globally occurring Oithona similis, together with the nauplii of various copepod species," after which a series of OA experiments were conducted "using these copepod species and life history stages to compare their response to future high CO2 conditions with natural under-ice pCO2 exposures."

What was learned
The five researchers report that their data revealed that "species and life stage sensitivities to manipulated conditions were correlated with their vertical migration behavior and with their natural exposures to different pCO2 ranges," noting that "vertically migrating adult Calanus spp. crossed a pCO2 range of >140 ľatm daily and showed only minor responses to manipulated high CO2," while "Oithona similis, which remained in the surface waters and experienced a pCO2 range of <75 ľatm, showed significantly reduced adult and nauplii survival in high CO2 experiments."

What it means
In light of these findings, Lewis et al. reached the obvious conclusion that "the natural range of pCO2 experienced by an organism determines its sensitivity to future OA," and that, "certainly, ubiquitous species in their adult form, living across a range of physicochemical conditions, are likely capable of surviving change." They also remark that "larvae of many marine organisms are released at very specific times to coincide with favorable environmental or food conditions," and it seems logical to conclude that the same would hold true in the future, making it easier for copepod larvae to survive future OA conditions as well.

Reviewed 29 January 2014