The goal of this proposal is to investigate the importance of environmental variables on the isotopic composition of major component biochemicals in phytoplankton. Specifically, the objective is to better understand how nutrient and light- limitations affects distributions and isotopic compositions of individual organic compounds in photosynthetic autotrophs. The study will assess the affects of nutrient limitation and representative species of the major algal biomarkers. To accomplish this, representative species of the major algal classes (i.e., Bacillariophyceace, Prymnesiophyceae, Cyanophyceae and Dinophyceae) will live chemostat growth chambers under a variety of conditions and their isotopic is to determine the effect of zooplankton grazing on the structure and isotopic compositions of lipids and pigments. This will be accomplished by allowing phytoplankton feedstock from one chemostat growth chamber to flow under controlled conditions into a second chamber containing zooplankton. Composition of algal biochemical will be compared with those of the zooplankton to investigate microbial chain interactions. The study includes degradation effects on isotopic compositions of algal biomarkers. Since herbivory is the most important 'sink' for autotrophic production, knowledge of structural/isotopic alterations during this process is critical for interpreting the distributions and isotopic compositions of algal degradation products in sinking and sedimentary organic matter. The baseline information provided by this research is needed to better interpret distributions of isotopic composition of lipids and pigments in particulate and sedimentary organic matter. Such information will ultimately make it possible to determine the source organisms for numerous biochemicals and to make significant advances in identifying processes driving recycling of organic carbon in the ocean.
