Two recent papers in Nature GeoScience demonstrate the real effects of ocean acidification. For those not in know, there is an ongoing decrease in the pH of the oceans from carbon dioxide released by humans into the atmosphere. From 1751 to 1994, the pH of the world’s oceans has dropped by 0.1, an considerable decrease considering that pH is a log scale. This results from the hydrolysis of CO2 which increases H+. That combined with the overall lowering of carbonate ions with the increase in aqueous CO2, makes calcification by marine organisms virtually impossible.
The first study deals with planktonic forams, single-celled critters responsible for 20-50% of total ocean carbonate flux. Yeah they are important. Looking at shell weights of Globigerina bulloides from the Southern Oceans from both today and the Holocene (~10,000), the team finds that weights have declined by 30-35%. For perspective think of how much you would weigh, if you lost 35% of your weight. Hell I’d be an underwear model! The team also correlates low shell weights with 50,000 year long record from a Southern Ocean core.
The second study uses a natural contrast in acidity in the deep sea. In the northwest Eifuku volcano in the Mariana arc the pH ranges from 5.36 to 7.29. In the common vent mussel, Bathymodiolus brevior, shell thickness and daily growth increments in shells from this area are half those from mussels living in water pH>7.8. The author suggest that the presence of 40 year old mussels only occurs because crabs are absent from the area sampled. Crabs agree, “Thin shelled vent mussels, Om nom nom nom.”
Orr, J., Fabry, V., Aumont, O., Bopp, L., Doney, S., Feely, R., Gnanadesikan, A., Gruber, N., Ishida, A., Joos, F., Key, R., Lindsay, K., Maier-Reimer, E., Matear, R., Monfray, P., Mouchet, A., Najjar, R., Plattner, G., Rodgers, K., Sabine, C., Sarmiento, J., Schlitzer, R., Slater, R., Totterdell, I., Weirig, M., Yamanaka, Y., & Yool, A. (2005). Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms Nature, 437 (7059), 681-686 DOI: 10.1038/nature04095
Tunnicliffe, V., Davies, K., Butterfield, D., Embley, R., Rose, J., & Chadwick Jr, W. (2009). Survival of mussels in extremely acidic waters on a submarine volcano Nature Geoscience DOI: 10.1038/ngeo500
Moy, A., Howard, W., Bray, S., & Trull, T. (2009). Reduced calcification in modern Southern Ocean planktonic foraminifera Nature Geoscience, 2 (4), 276-280 DOI: 10.1038/ngeo460