9633091 POPP The isotopic carbon composition of the marine phytoplankton reflects not only the isotopic composition of seawater but also the environmental conditions under which photosynthesis occurs. Oceanographers and paleontologists are particularly interested in how phytoplankton isotopic composition is related to ambient temperature so that fossil organic matter preserved in marine sediments might be used to infer climatic conditions in the geologic past. Because variety of factors is responsible for the algal isotopic composition actually found, there is a need to understand their individual and collective impact. This research team from the University of Hawaii and the Scotia Institute of Oceanography will use laboratory and field studies to examine how conditions such as physiological state, growth rate, and environmental conditions affect carbon isotopic 'fractionation' by the phyplankton. The laboratory studies will involve careful culture work with two algal species, and the results will be compared to samples collected from the water column and sediments of the Arabian Sea and at the Hawaiian Ocean Time-Series station near Oahu using a mathematical model relating various physiological and environmental factors to algal isotopic composition.
