|The coccolithophore Emiliania huxleyi is the most abundant calcifying phytoplankton species in the World's oceans. It is capable of growth at a wide range of salinities and temperatures, and due to its abundance and broad range, deep-sea export of its CaCO3 coccoliths plays a significant role in the oceans' alkalinity balance, and in turn, air-sea CO2 exchange. Since the start of the industrial age, atmospheric partial pressure of CO2 (pCO2) has steadily increased due to fossil fuel combustion and land use change, and is projected to reach 750 ppm by the end of this century. As a consequence, both seawater pH and carbonate ion concentration are expected to drop significantly relative to pre-industrial times. Calcifying organisms are sensitive to changes in carbonate ion concentration, however, neither the extent of this sensitivity, nor its physiological basis, are well understood.
The intent of this research is to examine how E. huxleyi physiologically acclimates and adapts to changes in its environment in order to understand the impact of changes in ocean carbonate chemistry on this major planktonic calcifying organism. Cells from two genetically distinct ecotypes (Type A & B) will be separately monocultured in chemostats across 3 levels of pCO2 under N or P limitation in short-term experiments to study acclimation and in long-term experiments under conditions of "present day" and projected "year 2100" ocean conditions to investigate adaptation responses to changing carbonate chemistry. Physiological performance (photosynthesis vs. irradiance) will be correlated with genome-wide patterns of gene expression using a whole genome microarray that has been developed by the E. huxleyi genome sequencing projects or using high-throughput sequencing approaches. In addition, cellular C, N & P and chlorophyll a will be measured as a means of tracking the nutrient status of cells.
Funded by the National Science Foundation