Approximately one third of carbon dioxide emissions dissolve in the surface waters of the ocean and increase its acidity (the phenomenon of ocean acidification). Amongst the biological effects of seawater acidification are changes in the growth of phytoplankton, organisms that are the basis for marine food-webs. However, variable effects on phytoplankton growth of increasing carbon dioxide concentration have been reported, including an increase, no effect or a decrease. The objective of this project is to understand the physiological response of marine phytoplankton to increasing concentrations of carbon dioxide and acidity. This knowledge will make it possible to assess, and eventually predict, future changes in phytoplankton ecology and ocean productivity. The hypothesis to be tested is that the increase in carbon dioxide and the increase in acidity (a decrease in pH) both influence the growth of marine phytoplankton. It is postulated 1) that elevated carbon dioxide levels will lead to a higher photosynthetic efficiency, and 2) that a lower pH of seawater will decrease the energy that phytoplankton must spend to maintain their normal internal pH. Experiments will be carried out to test if differences in photosynthetic and respiratory physiology between phytoplankton species will result in different responses to carbon dioxide concentration and ocean acidity. These hypotheses will be tested in laboratory experiments and complementary field studies, using mass spectrometric techniques and the analysis of molecular markers to trace carbon and oxygen metabolism. Field experiments with natural phytoplankton will be carried out in New Jersey coastal waters, Bermuda, and iron-limited waters off California.
Broader Impacts This project, which addresses an issue of significant concern to society, will provide research experiences for undergraduates and training for graduate students and a postdoctoral fellow. Summer interns from local junior colleges will participate in the project. A problem-based learning package on climate change and ocean acidification targeting middle and high school students and teachers will be developed. The principal investigators will work with Climate Central, a nonprofit organization that prepares media content for the web, television stations and other outlets that provide information to the public.
