Date of Award

8-2008

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

Howard Patterson

Second Committee Member

Collin Roesler

Third Committee Member

William Halteman

Abstract

This study was undertaken to use algal chlorophyll fluorescence as a diagnostic tool for stress. Uni-algal cultures of Ankistrodesmus falcatus (Chlorophyceae) and field samples containing mixed algal assemblages were used to determine if additions of CuSO4 or carbaryl caused immediate changes in chlorophyll chemistry resulting in variations in vivo fluorescence intensity. A. falcatus cultures were grown in two freshwater media types, Bold's Basal Media (BBM) and DY-V media. The use of cultures grown in the presence (DY-V) or absence (BBM) of a chelating agent (EDTA) and the use of field samples containing dissolved organic matter (DOM) allowed for interpretations based on available Cu. Analyses were performed based on emission spectra with excitation at 435 nm (corresponding to chlorophyll a) using a spectrofluorometer. Fluorescence experiments performed on A. falcatus cultures grown in BBM were coupled with cell counts and chlorophyll measurements. The ratio of fluorescence to cell counts (F:cell), fluorescence to chlorophyll (F:chl), and chlorophyll to cell counts (Chl:cell) were calculated. The chl:cell data were not significantly different within or between dates. FLH is a relative measure of chlorophyll fluorescence in the chlorophyll fluorescence emission band at 682 nm. Calculated normalized fluorescence line height (FLH) values at 682 nm were corrected for changes in fluorescence as a function of time, removing the effect of changing biomass over time, and were normalized to the initial culture fluorescence (estimated initial biomass). This research showed increases and decreases in F:cell ratios and normalized FLH values. A. falcatus cultures grown in BBM had the same trend when analyzed using median Fxell ratios or median normalized FLH values. Normalized FLH values therefore could be used in place of F:cell ratios when cell counts were unavailable. All CUSO4 treatments increased these median values. A. falcatus cultures grown in DY-V media decreased the median normalized FLH values for all CuSO4 treatments. Regardless of media type, cultures treated with CuSO4 had an initial saturation value (additions above this value did not cause an additional response) and a critical value (additions above this value caused an additional response). Field samples treated with CuSO4 were more variable than culture experiments. The amount of available CuSO4 was lower in field samples and DY-V media than in BBM due to Cu-DOM or Cu-EDTA binding. Low Cu concentrations potentially increased photosynthesis and/or heat dissipation consequently decreasing fluorescence. Higher Cu concentrations caused stress to the algae; the photosynthetic capacity was reduced and resulted in increased in vivo fluorescence intensity. Low Cu concentrations had the opposite effect on chlorophyll fluorescence compared to high Cu concentrations. DY-V media treated with carbaryl quenched algal fluorescence at a critical value of 75 ppm. Carbaryl treatments caused a decrease in fluorescence for 89% of treatments. Since the chl:cell ratios remained constant for all treatments, physiological responses in the form of F:cell ratios and normalized FLH values were solely attributed to Cu or carbaryl additions. Overall, fluorescence response was a function of sample type, substrate, pesticide, and concentration.

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