Environmental Causes of Pigment Heterogeneity In Phytoplankton Species

In our lab, techniques were implemented to build an instrument with the ability to identify single-cells of phytoplankton species based on the presence of different types of pigments within each cell. Classifying phytoplankton species is important to understand biogeochemical cycles and the pelagic food chain system in the ocean, which could be manipulated by several environmental influences including nutrient availability, temperature, carbon dioxide levels, and light availability. Environmental influences have the ability to change physiological features of phytoplankton cells including size, pigmentation, elemental requirements, cellular functions, and composition. It is important to understand these changes because they influence phytoplankton community structure, which effects primary production, food web dynamics and structure, and biogeochemical cycles. The aim of this research was to determine the mechanisms by which pigments in phytoplankton change in response to environmental influences. Theoretical and experimental work was performed to examine the effect of factors on pigments. Investigations were performed to see if and how low/high conditions of nitrogen and phosphorus affect the pigments within a phytoplankter cell. Experiments involved techniques to monitor biomass, through cell counting and fluorometry, and pigmentation with high-performance liquid chromatography and fluorescence spectroscopy. High-performance liquid chromatography determined pigment types present in cells and the various pigment concentrations to determine if the pigment types changed in the cell, pigment degradation occurred, or pigment concentrations increased or decreased. Fluorescence spectroscopy was used to see if the phytoplankton were affected by changes in their environment and how they were affected by focusing on the changes in the shape of the fluorescence excitation spectra. Theoretical work was performed to observe how the electronic spectrum of chlorophyll a was affected by metal substitution with magnesium and if an exchange could occur between magnesium and other heavy metals. In this research, methods of chemometrics were used to build a calibration model to use size as another aspect for classifying phytoplankton species with the in-house built shipboard fluorescence imaging photometer. Research applications involve classifying phytoplankton on a single-cell basis properly through the use of fluorescence excitation spectroscopy and cell size and to use phytoplankton as a sensor to characterize community structure