Fluorescence characteristics of picocyanobacteria: Effects of light and nitrogen availability.

Abstract

The general objective of this thesis was to examine the effects of key environmental variables on fluorescence characteristics of picocyanobacteria using both culture and field experiments. Fluorescence ratios of phycoerythrin (PE) to phycocyanin (PC), and PE to Chl a, were found to be good surrogates of pigment ratios. The severity of nitrogen stress, as measured by the reduction in carbon to nitrogen ratios, PBP, and fluorescence ratios, appeared to be related to the pigment types of picocyanobacteria. Only slight changes in fluorescence ratios can be expected between high full spectrum and low monochromatic growth irradiance (PSII light) as a result of the small differences in PUR between these two environments. The fluorescence characteristics of low light acclimated picocyanobacteria can also be significantly influenced by growth rate. Depth patterns in fluorescence ratios in response to light and nitrogen availability were found to be consistent with differences in the seasonal and between-lake abundance of two populations of PE-picocyanobacteria. (Abstract shortened by UMI.)