Monterey Bay Aquarium Research Institute

Jonathan Erez, Ph.D

Institute of Marine Sciences, The Hebrew University of Jerusalem

Biomineralization Processes in Corals and Foraminifera
in View of Ocean Acidification

The lanktonic foraminiferan Globigerinoides sacculifer and its symbiotic algae
A single polyp of the coral Stylophora pistillata showing its symbiotic algae

Wednesday- July 2, 2008

Pacific Forum – 3:00 p.m.

Biomineralization of calcium carbonate (CaCO3) is a major process in the global carbon cycle. Reef building corals and foraminifera (marine protozoa) are important CaCO3 producing organisms that thrive in the oceans. Atmospheric carbon dioxide (CO2) increase lowers the pH of the surface ocean and consequently these organisms show dramatic decrease in their rates of calcification. Using confocal microscopy and micro-sensors for the carbonate chemistry we show that the sensitivity of corals and foraminifera to ocean acidification can be explained by their calcification physiology, which involve direct input of seawater into the site of biomineralization. In both groups the main modification that the organisms exert on the seawater is an elevation of pH by roughly 1 pH unit relative to ambient levels. Ocean acidification increases the pH elevation gap as well as the buffer capacity of the seawater. Thus even a small pH decrease of 0.2-0.3 pH units is strongly affecting the calcification rates. The global implications of these findings will be discussed.


Next: July 9 - Jim Barry, Ph.D.