Graduate Thesis Or Dissertation

 

Responses of algal populations to parasitism by Aphelidium chlorococcarum and chytrids in an Oregon sewage lagoon Público Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/2b88qg99v

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  • The abundance of algal species and their parasites was monitored weekly for two years in a sewage lagoon at the Corvallis Airport, Oregon. During the cooler months, Euglena species were dominant followed by a Chlamydomonas assemblage in the spring and a predominantly Scenedesmus assemblage in the summer and fall. Parasites infected 14 of the 35 most abundant species of algae. An unidentified chytrid parasitized Scenedesmus obliguus, and a Rhizophydium sp. infected Chlamydomonas species. The most common parasite, Aphelidium chlorococcarum Fott, infected 11 species, particularly species of Scenedesmus. Aphelidium chlorococcarum was isolated in culture for morphological and ultrastructural study. Reclassification of Aphelidium as an Olpidiaceous chytrid was recommended. Only very severe infections had a significant impact on host populations and these were rare. Aphelidium chlorococcarum infected less than 10% of the host populations most of the year. The most severe infection observed (74%) was followed by a sharp decrease in the population of S. armatus for a month. Other declines after severe parasitism were small and lasted approximately one week. Certain climatological, chemical, and biological factors were related to the occurrence of severe infections. Of these, a dense host population favored severe parasitism the most. Increased precipitation was also associated with severe infections in the fall.
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