Abstract

The future consequences of ocean acidification for marine ecosystems are difficult to assess, in part because laboratory experiments are limited by their necessary short time-scales and reduced ecologic complexity. In contrast, the geological record is replete not only with a variety of global environmental perturbations that may include ocean acidification, but also associated biotic responses including adaptation and evolution. However, for the geological record to provide future-relevant information about potential species and ecosystem responses, qualitatively (and ideally quantitatively)similar changes in carbonate chemistry to those projected for the future, must have occurred. For long-term (million year) intervals of quasi steady state in throughput of carbonate carbon weathering vs.sedimentary burial), we already know that high pCO2 and low ocean surface pH does not imply reduced carbonate saturation and hence pressure on marine calcifiers, although this issue continues to cause confusion in the climate change debate. Rapid, future-like events in contrast, are characterized by a strong coupled decline in both pH and saturation in response to CO2 emissions. I this talk I will address the questions: at what rate of atmospheric pCO2 change does ocean acidification become qualitatively similar to current and future changes, and have any events in the geological past exhibited the characteristics of anthropogenic ocean acidification?