Determining the role of the ocean in climate and the global carbon cycle is an essential part of the effort to understand natural climate change. Chemical analyses of microscopic shells preserved in deep-sea sediments provide key records of changes in deep-water chemistry, circulation, and temperature in the past. To be confident in these microfossil-based paleoceanographic records, the shell-chemistry response to environmental conditions must be carefully calibrated. In this project, we will carry out chemistry calibrations of shell oxygen isotopic and Mg/Ca composition using multiple-temperature laboratory cultures of deep-sea benthic foraminifera. The experiments will use live benthic foraminifera collected each year from continental shelf and deep-sea (500-2000 m water depth) sites. Additional experiments will establish optimal culturing conditions for the deep-water benthic foraminiferal taxa most often used in paleoceanographic reconstructions. This study will provide new calibrations of two important deep water "paleothermometers" the oxygen isotopic composition and magnesium:calcium ratios of deep-sea benthic foraminifera. Our culture-based estimates will provide a unique independent test of the field-based calibrations that provide the foundation for reconstructions of deep-water temperature. The broader impacts of this project include inclusion of undergraduate volunteers from non-oceanographic colleges and universities as cruise participants, to introduce them to at-sea oceanographic research.
