Responses of target and non-target species to algaecide exposures

Laboratory experiments are often used to predict the responses of target and non--]target species to chemical exposures in the field. In the first two experiments of this thesis, a rigorous evaluation of six algal viability measures was conducted. A definitive evaluation of the algal response measures was conducted using heat treatment to create known live: dead cell suspensions. Results from the response measures were compared to the known viability of the cell suspensions to determine their variance and accuracy. Copper-based algaecides were then used as a more realistic exposure to test the algal viability measures. When algal viability measures had a monotonic response curve, EC 50s and potency slopes were calculated to compare the relative sensitivities of Planktothrix agadhii and Pseudokirchneriella subcapitata to copper sulfate pentahydrate and Cutrine-Ultra. Lastly, experiments were conducted in the laboratory to predict the responses of target and non--]target organisms in Lay Lake to an ongoing algaecide treatment and a potential alternative algaecide treatment for Lyngbya wollei (L. wollei ). Lay Lake is a man-made reservoir in central Alabama that has experienced noxious L. wollei growths for the past 10 years. Results from the first two experiments highlight the advantages, limitations and utility of some algal viability measures. In the last experiment, no measureable copper residuals were present and no adverse effects to benthic invertebrates ( Hyalella azteca and Chironomus dilutus) were discerned from sediments after 10 years of periodic algaecide applications. An effective alternative treatment for L. wollei from Lay Lake was predicted that may enhance the margin of safety for non-target species in the field.