How does rising atmospheric CO2 affect marine organisms?

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Effects of Parental Environment on the Progeny of Coral Reef Fish
Miller, G.M., Watson, S.-A., Donelson, J.M., McCormick, M.I. and Munday, P.L. 2012. Parental environment mediates impacts of increased carbon dioxide on a coral reef fish. Nature Climate Change 2: 858-861.

The authors write that "a major limitation to predicting the effects of increasing [atmospheric] CO2 concentrations on marine species and ecosystems is the lack of information on acclimation or adaptation to increased CO2 over timescales relevant to climate change predictions," while indicating "there is increasing evidence that the capacity for acclimation to environmental stress may depend on the history of previous life stages (Marshall and Morgan, 2011; Parker et al., 2012)."

What was done
In a study designed to further explore this subject, Miller et al. conditioned adult anemonefish, Amphiprion melanopus, to present-day (430 ppm), moderate (581 ppm) and high (1,032 ppm) CO2 treatments - "consistent with projections for CO2 concentrations in the atmosphere and ocean over the next 50-100 years" - where the fish were allowed to spawn naturally, after which juvenile fish from control parents were reared at either the control CO2 or transferred to high CO2 at each of three temperatures (28.5, 30.0 and 31.5°C), while "juveniles from parents in the moderate- and high-CO2 treatments were reared in similar CO2 conditions as their parents at each of the three temperatures."

What was learned
The five Australian researchers report that "ocean conditions projected for the end of the century (approximately 1,000 ppm CO2 and a temperature rise of 1.5-3.0°C) cause an increase in metabolic rate and decreases in length, weight, condition and survival of juvenile fish," which sounds pretty serious, if not downright deadly. However, they found that "these effects are absent or reversed when parents also experience high CO2 concentrations," indicative of the fact that "conditions experienced by adults can have significant carry-over effects on the performance of their offspring (Bonduriansky and Day, 2009; Marshall and Morgan, 2011; Donelson et al., 2012), often leading to improved capacity to cope with environmental stress (Bernardo, 1996; Donelson et al., 2009)."

What it means
On the basis of their several observations, Miller et al. conclude that "parental effects prepare juveniles for similar conditions to those experienced in the parental generation," and, therefore, they suggest that "non-genetic parental effects can dramatically alter the response of marine organisms to increasing CO2 and demonstrate that some species have more capacity to acclimate to ocean acidification than previously thought."

Bernardo, J. 1996. Maternal effects in animal ecology. American Zoologist 36: 83-105.

Bonduriansky, R. and Day, T. 2009. Nongenetic inheritance and its evolutionary implications. Annual Review of Ecology, Evolution and Systematics 40: 103-125.

Donelson, J.M., Munday, P.L. and McCormick, M.I. 2009. Parental effects on offspring life histories: when are they important? Biology Letters 5: 262-265.

Donelson, J.M., Munday, P.L. and McCormick, M.I. 2012. Rapid transgenerational acclimation of a tropical reef fish to climate change. Nature Climate Change 2: 30-32.

Marshall, D.J. and Morgan, S.G. 2011. Ecological and evolutionary consequences of linked life-history stages in the sea. Current Biology 21: R718-R725.

Parker, L.M., Ross, P.M., O'Connor, W.A., Borysko, L, Raftos, D.A. and Portner, H.-O. 2012. Adult exposure influences offspring response to ocean acidification in oysters. Global Change Biology 18: 82-92.

Reviewed 10 April 2013