Project: Impact of Ocean Acidification on Planktonic Foraminifera in the California Current System During the Last 300 Years

NSF Abstract:

More than one-quarter of anthropogenic CO2 emissions produced since the beginning of the Industrial Revolution have been incorporated into the global surface ocean causing large-scale declines in seawater pH. This phenomenon is referred to as ocean acidification (OA) and is predicted to become particularly acute in coastal regions, including the west coast of the US. As the oceans become more acidic, it will become increasingly difficult for marine calcifiers to produce their shells. This may have important consequences for the marine food web and for various commercially important marine species. This study will produce the first detailed record of changes in OA along the coast of California during the last two centuries. This will be accomplished by examining the shells of a group of calcifying plankton called foraminifera. These organisms live and produce their shells at the sea surface, with the shells sinking to the sea floor when the organism dies. Foraminiferal shells from a sediment core collected from Santa Barbara Basin will be studied in order to reconstruct changes in calcification over the last 200 years. Using these results, predictions will be made as to how calcification will continue to change through the end of the 21st century based on various scenarios for increasing atmospheric CO2.

Modeling studies suggest that the California Current System (CCS) and associated ecosystem have been and will continue to be particularly vulnerable to ocean acidification (OA). To test this concept, this study will quantify the effect of OA on calcification rates in planktonic foraminifera from the Santa Barbara Basin region of the CCS since the onset of the Industrial Revolution. A 20-year Santa Barbara Basin sediment trap time series, together with the varved sediments from the basin will be used to generate a nearly annually resolved record of changes in calcification for this group of plankton in the CCS for the last 200 years. The proposed research will take place in two phases. First, sediment trap samples and coincident water column chemistry data will be used to calibrate the relationships among foraminiferal shell morphology (area density), shell geochemistry (B/Ca), and water column carbonate chemistry. Second, these morphologic and trace metal proxies will be used to produce two independent records of changing carbon ion concentration for the last two centuries using a 210Pb-dated varved sediment record. These sediment-derived estimates of carbon ion concentration will be compared with model estimates of this parameter for the last two centuries. Taken together, the sediment trap and core samples will provide an incomparable archive for quantifying the impact of OA on calcification in this paleoclimatically important group of plankton.