How does rising atmospheric CO2 affect marine organisms?

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Shrinking Salamanders! ... A Rapid Response to Global Warming
Caruso, N.M., Sears, M.W., Adams, D.C. and Lips, K.R. 2014. Widespread rapid reductions in body size of adult salamanders in response to climate change. Global Change Biology 20: 1751-1759.

The authors indicate that "salamanders in the genus Plethodon are particularly sensitive to warming and drying trends as they are terrestrial, lung-less organisms completely dependent upon cutaneous respiration for gas exchange and water uptake," citing Wells (2007). And they say that "because changes in body size are predicted as a major response to global climate change (Daufresne et al., 2009)," they decided to test "whether shifts in mean body size have occurred in populations of Appalachian woodland salamanders" over the past 55 years.

What was done
During June-October 2011 and March-June 2012, Caruso et al. resurveyed 78 historic collecting sites comprised of 212 populations of 15 Plethodon taxa once in each season (Spring, Summer, Fall), in order to compare contemporary with historic size measurements of the past half-century.

What was learned
The four researchers say there was "an 8% reduction in the average adult body size across all species over the 55-year study period," which trend remained significant even after they removed the contemporary field measurements. More specifically, they say they "detected reductions of 2% (P. cheoah), 3% (P. jordani), 6% (P. ventralis), 7% (P. cinereus, P. cylindraceus), and 18% (P. yonahlossee)," while only one species (P. welleri) increased in size, and that by only 2%. In addition, they report that body size change was most accentuated in regions that have become both warmer and drier over the past 55 years.

What it means
In the concluding words of Caruso et al., "the rapidity and the widespread extent of these changes across so many species in a biodiversity hotspot may signal rapid adaptation to novel environmental conditions."

Daufresne, M., Lengfellner, K. and Sommer, U. 2009. Global warming benefits the small in aquatic ecosystems. Proceedings of the National Academy of Sciences USA 106: 12,788-12,793.

Wells, K.D. 2007. The Ecology and Behavior of Amphibians. The University of Chicago Press, Chicago, Illinois, USA.

Reviewed 10 September 2014