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# The effects of atrazine on the competitive interactions of three green algae

 dc.contributor.author Simmons, Norman Kent en_US dc.date.accessioned 2007-05-15T15:21:40Z dc.date.available 2007-05-15T15:21:40Z dc.date.issued 1997-05-01T00:00:00Z en_US dc.identifier.uri http://hdl.handle.net/1993/929 dc.description.abstract The toxic effects of the herbicide Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) on the three common fresh water phytoplankton species Scenedesmus quadricauda, Chlamydomonas musicola, and Chlorella vulgaris were examined. Initially the EC50 values for atrazine were determined for each species using standard batch culture methods. The EC50 values were then recalculated from growth data taken from unialgal continuous culture experiments, and a comparison was made between the results of these two bioassay protocols. The species were then grown in pairs, in continuous cultures, in competition for phosphate. From cell density data the competition coefficients ($\alpha\sb{1,2}$ and $\alpha\sb{2,1}$ were determined. The competitive cultures were exposed to concentrations of atrazine ranging from 0 to $1.0\times 10\sp{-6}$ mol/L. From these experiments it was possible to describe the pattern of changes in the competition coefficients with changes in levels of atrazine exposure for each of the test species pairs. Finally series of model equations were developed from the empirical data and a series of computer simulations were used to predict the outcomes of competition at different initial population densities and differing atrazine exposures. In all species pairs tested the alpha value dose responses showed a biphasic pattern, with a threshold which coincided with the thresholds of the physiological responses seen i the unialgal experiments. These alpha value dose responses led to competitive outcomes and species compositions that were not predicted from the single species toxicological tests. This multispecies competitive bioassay, holds the promise of predicting community level toxicological responses. en_US dc.format.extent 9216943 bytes dc.format.extent 184 bytes dc.format.mimetype application/pdf dc.format.mimetype text/plain dc.language en en_US dc.language.iso en_US dc.rights info:eu-repo/semantics/openAccess dc.title The effects of atrazine on the competitive interactions of three green algae en_US dc.type info:eu-repo/semantics/doctoralThesis dc.degree.discipline Botany en_US dc.degree.level Doctor of Philosophy (Ph.D.) en_US
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