How does rising atmospheric CO2 affect marine organisms?

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The Likely Fate of Sea Stars in an Acidifying and Warming Ocean
Nguyen, H.D. and Byrne, M. 2014. Early benthic juvenile Parvulastra exigua (Asteroidea) are tolerant to extreme acidification and warming in its intertidal habitat. Journal of Experimental Marine Biology and Ecology 453: 36-42.

The authors write that "intertidal rock pool invertebrates experience large variations in environmental conditions that coincide with daily changes in tide levels, particularly temperature, pH and salinity (Truchot and Duhamel-Jouve, 1980)." And they state that "as a result of adaptation to tolerate environmental extremes (Byrne, 2011; Melzner et al., 2009; Sanford and Kelly, 2011), these animals are considered to be comparatively robust to these stressors." Nevertheless, they note that (1) "the early juvenile is one of the least understood life stages of marine invertebrate biology/ecology" and that (2) "there is a paucity of data on the impacts of environmental stressors on juvenile development."

What was done
In the words of Nguyen and Byrne, "to determine the potential impact of acidification and warming on a conspicuous component of the temperate intertidal fauna of the southern hemisphere, the response of newly metamorphosed juvenile (ca. 450 µm diameter) sea stars (Parvulastra exigus) to increased acidification and temperature was investigated with respect to conditions recorded in the habitat (+ 2-4°C, - 0.4-0.6 pH units)."

What was learned
The two Australian researchers report that after a 4-week incubation period under various experimental conditions, negative effects on juvenile development and growth were only observed at a pH of 7.2 (a decrease of one full unit), which was brought about by pCO2 values in the range of 4430-4600 µatm.

What it means
In light of what they observed, Nguyen and Byrne say their data show that "P. exigua juveniles are robust to a 4°C warming, a scenario projected for the region by 2100 (Ridgway, 2007)," and that it thus appears that "P. exigua and other stress tolerant intertidal species may have pre-adaptive traits (Sanford and Kelly, 2011) that will convey resilience to near-future ocean change."

Byrne, M. 2011. Impact of ocean warming and ocean acidification on marine invertebrate life history stages: vulnerabilities and potential for persistence in a changing ocean. Oceanography and Marine Biology: An Annual Review 49: 1-42.

Melzner, F., Gutowska, M.A., Langenbuch, M., Dupont, S., Lucassen, M., Thorndyke, M.C., Bleich, M. and Portner, H.O. 2009. Physiological basis for high CO2 tolerance in marine ectothermic animals: pre-adaptation through lifestyle and ontogeny? Biogeosciences 6: 2313-2331.

Ridgway, K.R. 2007. Long-term trend and decadal variability of the southward penetration of the East Australian current. Geophysical Research Letters 34: 10.1029/2007GL030393.

Sanford, E. and Kelly, M.W. 2011. Local adaptation in marine invertebrates. Annual Review of Marine Science 3: 509-535.

Truchot, J.P. and Duhamel-Jouve, A. 1980. Oxygen and carbon dioxide in the marine intertidal environment: diurnal and tidal changes in rock pools. Respiration Physiology 39: 241-154.

Reviewed 6 August 2014