How does rising atmospheric CO2 affect marine organisms?

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CO2-Enriched Seawater and the Self-Righting Ability of Gastropods
Manriquez, P.H., Jara, M.E., Mardones, M.L., Navarro, J.M., Torres, R., Lardies, M.A., Vargas, C.A., Duarte, C., Widdicombe, S., Salisbury, J. and Lagos, N.A. 2013. Ocean acidification disrupts prey responses to predator cues but not net prey shell growth in Concholepas concholepas (loco). PLOS ONE 8: e68643.

The authors write that in Chile "the gastropod Concholepas concholepas is both an economically and ecologically important species inhabiting subtidal and intertidal marine habitats." But they indicate that in these rocky environments, "the gastropods are often exposed to highly turbulent conditions," during which times they adhere tightly to the rock surface with their foot. However, they add that "when feeding and handling prey items the foot of C. concholepas is often removed from the rock leaving it vulnerable to being dislodged," and to thereby becoming someone else's meal themselves. Thus, it is in the gastropod's best interests to right itself as quickly as possible whenever this occurs.

What was done
To explore the impacts of ocean acidification on this self-preservation response, as well as the more basic phenomena of growth and calcification, Manriquez et al. collected small individuals of C. concholepas from a rocky intertidal area in northern Chile, transported them to a laboratory where they were reared in natural seawater for a period of one month, after which ten individuals were randomly assigned to one of three pCO2 concentrations: 388 ľatm (current), 716 ľatm (medium) or 1036 ľatm (high). There they remained, under well-fed conditions, for a period of 83 days, while various measurements were made of them on days 0, 11, 45, 52, 62, 73 and 83 after the beginning of treatments.

What was learned
At the end of the study period, the eleven researchers report there were no significant among-treatment differences in peristomal length, wet weight and buoyant weight, as well as the shell weight of empty shells. They also determined that, "on average, self-righting time was three times faster in individuals reared under increased pCO2 levels than under normal seawater conditions."

What it means
Manriquez et al. conclude that "C. concholepas have the ability to maintain calcification even at pCO2 levels of 1036 ľatm ... in agreement with similar results reported in the literature for other invertebrates (Ries et al., 2009; Manzello, 2010; Rodolfo-Metalpa et al., 2011)." And they say that "during their early ontogeny, exposure to elevated pCO2 may actually increase the likelihood of C. concholepas surviving after being overturned by an exogenous cause."

Manzello, D.P. 2010. Ocean acidification hot spots: Spatiotemporal dynamics of the seawater CO2 system of eastern Pacific coral reefs. Limnology and Oceanography 55: 239-248.

Ries, J.B., Cohen, A.L. and McCorkle, D.C. 2009. Marine calcifiers exhibit mixed responses to CO2-induced ocean acidification. Geology 37: 1131-1134.

Rodolfo-Metalpa, R., Houlbreque, F., Tambutte, E., Boisson, F., Baggini, C., Patti, F.P., Jeffree, R., Fine, M., Foggo, A., Gattuso, J.P. and Hall-Spencer, J.M. 2011. Coral and mollusk resistance to ocean acidification adversely affected by warming. Nature Climate Change 1: 308-312.

Reviewed 13 November 2013