How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

Purple Sea Urchins: Primed for Rapid Evolution in Acidifying Seas
Pespeni, M.H., Sanford, E., Gaylord, B., Hill, T.M., Hosfelt, J.D., Jaris, H.K., LaVigne, M., Lenz, E.A., Russell, A.D., Young, M.K. and Palumbi, S.R. 2013. Evolutionary change during experimental ocean acidification. Proceedings of the National Academy of Sciences USA 110: 6937-6942.

The authors write that "little is known about the adaptive capacity of species to respond to an acidified ocean," and, as a result, they say that "predictions regarding future ecosystem responses remain incomplete." But that can be changed; and they therefore set about to do so, in a study that demonstrates that ocean acidification generates striking patterns of genome-wide selection in purple sea urchins (Strongylocentrotus purpuratus) cultured under different CO2 levels of 400 and 900 ppm.

What was done
Working with seven different populations collected along a 1,200-km mosaic of coastal upwelling-driven acidification of the California Current System, Pespeni et al. combined (1) sequencing across the transcriptome of the purple sea urchin, (2) growth measurements under experimental acidification, and (3) tests of frequency shifts in 19,493 polymorphisms during development, while detecting in the process "the widespread occurrence of genetic variation to tolerate ocean acidification."

What was learned
The eleven researchers report that although larval development and morphology showed little response to elevated CO2, they found "substantial allelic change in 40 functional classes of proteins involving hundreds of loci." More particularly, they state that "pronounced genetic changes, including excess amino acid replacements, were detected in all populations and occurred in genes for biomineralization, lipid metabolism, and ion homeostasis - gene classes that build skeletons and interact in pH regulation," while noting that "such genetic change represents a neglected and important impact of ocean acidification that may influence populations that show few outward signs of response to acidification."

What it means
Quoting the researchers themselves, "our results demonstrate the capacity for rapid evolution in the face of ocean acidification and show that standing genetic variation could be a reservoir of resilience [our italics] to climate change in this coastal upwelling ecosystem."

Reviewed 11 September 2013