How does rising atmospheric CO2 affect marine organisms?

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Impacts of Rising Atmospheric CO2 on the Serpent Starfish
Wood, H.L., Spicer, J.I., Lowe, D.M. and Widdicombe, S. 2010. Interaction of ocean acidification and temperature; the high cost of survival in the brittlestar Ophiura ophiura. Marine Biology 157: 2001-2013.

What was done
In a study designed to examine the effects of the twin environmental evils of our day - ocean warming and ocean acidification - Wood et al. (2010) studied a number of physiological parameters in the serpent starfish (Ophiura ophiura). In doing so, they collected 96 individuals with a disc diameter between 10 and 15 mm from Cawsand Bay, Plymouth Sound (50°09.77' N, 4°11.50' W), after which they exposed the brittlestars to three different pH treatments (pH of 8.0, 7.7 or 7.3) and two different temperature treatments (10.5°C or 15°C) for a period of 40 days. Measured parameters included metabolism, calcification, mortality, motility, arm structure, and arm regeneration, the latter of which parameters was studied by removing either 10, 20, 30, or 40 mm of arm length on one of the animals' arms.

What was learned
Results of the experiment revealed the following: (1) survival was "100% at both temperatures and across all pH treatments," (2) metabolic rate increased as pH decreased in the low temperature treatment, while there was no significant difference across the different pH treatments in the high temperature regime, (3) muscle appearance and density did not change over either the temperature or pH treatment ranges in established or regenerated arms, (4) a faster response time in movement (motility) was observed at low temperature and low pH, (5) brittlestars across "all treatments had the same net calcification throughout the experiment," (6) arm regeneration rate within the low temperature treatment was "unaffected by the length of arm lost and the rate was similar between all pH treatments," (7) arm regeneration rate was significantly faster at higher temperatures than lower temperatures.

What it means
In light of the above findings, it would appear that the serpent starfish should be able to successfully cope with the physiological changes brought about by any modest temperature increase and/or pH decline likely to occur in the future.

Reviewed 28 September 2011