Date of Award

2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

College of Graduate Studies

First Advisor

Peter D. R. Moeller

Second Advisor

Paul V. Zimba

Third Advisor

Steven J. Christopher

Fourth Advisor

Erika E. Büllesbach

Fifth Advisor

Alicja Bielawska

Abstract

The golden alga Prymnesium parvum has been implicated in fish and aquatic animal kills globally for over a century. In addition to widespread ecological impacts through the loss of entire fish populations within lakes, an economic burden is also felt by state and local agencies due to losses of fish raised for stocking lakes and the loss of fishing and recreational use of the affected water body. Multiple compounds have been implicated in P. parvum toxicity, but the unequivocal identification and characterization of all P. parvum toxins remains to be accomplished. In this work we isolated and structurally characterized toxic metabolites from P. parvum, examining uni-algal laboratory cultures and field collections of algal biomass from fish kill sites. An aggregate of saturated and unsaturated acyl amides are a previously undescribed class of P. parvum toxins. The amount of acyl amides present at multiple P. parvum bloom sites and reference sites was quantified. Further analysis of these compounds through selected bioassays demonstrated that acyl amides were cytotoxic, hemolytic, and ichthyotoxic, with the gill as the site of action. In addition, we demonstrated that the presence of divalent cations and increased pH significantly increased the toxicity of unsaturated acyl amides. Moreover, increased pH decreased the toxicity of fatty acids, a class of compounds previously implicated in P. parvum toxicity. Multiple abiotic and biotic factors are associated with P. parvum blooms and the toxicity of these blooms. We analyzed the effect of multiple physicochemical parameters on the toxicity of acyl amides using an artificial neural network and linear statistical tests. Our results demonstrated that increasing pH is significantly associated with an increase in the toxicity of acyl amides. Mixtures of environmentally relevant concentrations of unsaturated acyl amides at ecologically relevant pH levels resulted in a significant loss of viability of rainbow trout gill cells. Our results have identified a new toxin class from P. parvum. This is the first report to demonstrate that a toxin class implicated in P. parvum toxicity accumulates to lethal levels in the environment. We have developed a new method for analyzing complex mixtures that can be utilized to assess the effect of multiple chemical and physical factors on toxicity. These results highlight the potential role of physicochemical factors and their effect on algal toxins after they are released into the environment, illustrating the necessity to examine toxin chemistry in an environmentally relevant context.

Rights

All rights reserved. Copyright is held by the author.

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