Ecophysiology and Toxigenicity of Cyanobacterial Assemblages: Molecular Insights into Toxin Production - with Emphasis on Microcystins
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Otten, Timothy Gerald. Ecophysiology and Toxigenicity of Cyanobacterial Assemblages: Molecular Insights Into Toxin Production - with Emphasis On Microcystins. University of North Carolina at Chapel Hill, 2012. https://doi.org/10.17615/8tr0-bg64APA
Otten, T. (2012). Ecophysiology and Toxigenicity of Cyanobacterial Assemblages: Molecular Insights into Toxin Production - with Emphasis on Microcystins. University of North Carolina at Chapel Hill. https://doi.org/10.17615/8tr0-bg64Chicago
Otten, Timothy Gerald. 2012. Ecophysiology and Toxigenicity of Cyanobacterial Assemblages: Molecular Insights Into Toxin Production - with Emphasis On Microcystins. University of North Carolina at Chapel Hill. https://doi.org/10.17615/8tr0-bg64- Last Modified
- March 22, 2019
- Creator
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Otten, Timothy Gerald
- Affiliation: Gillings School of Global Public Health, Department of Environmental Sciences and Engineering
- Abstract
- Cyanobacterial harmful algal blooms (CHABs) are occurring at increasing frequencies worldwide due to nutrient over-enrichment, warmer temperatures and continued alteration of the natural hydrology of aquatic ecosystems. In drinking water reservoirs the nearly ubiquitous toxin-producer, Microcystis spp., is an increasingly worrisome water quality problem and health hazard. China‟s third largest lake, Taihu, has been experiencing progressively worse cyanobacterial blooms over the past three decades. Whole lake monitoring was conducted in 2009 – 2010, in order to characterize the phytoplankton communities and their cyanotoxic potentials; as well as to identify the environmental factors promoting toxigenic Microcystis blooms over nontoxic ecotypes. Taking this concept one step further; this research also investigated the role of transposable elements in shaping the distribution of the microcystin synthetase (mcy) operon throughout the genus Microcystis. Microcystins are potent hepatotoxins that are also believed to be involved in intracellular stress response. A possible alternative stress response mechanism employed by non-microcystin producing strains is discussed. This work identified four Microcystis morphospecies comprising the summer blooms in Taihu, two of which (M. aeruginosa and M. flos-aquae) were capable of microcystin production. Water temperature was found to influence bloom formation and morphospecies prevalence, with cooler temperatures promoting toxin producing strains of Microcystis. Additionally, low nitrogen (N) to phosphorus (P) ratios (replete N & P) appeared to select for toxigenic populations of Microcystis spp., whereas nontoxic strains were dominant in nutrient limited regions of the lake. Chlorophyll a (Adj. R2 = 0.83, p < 0.0001) was equally predicative of microcystin variance across the lake as fluorescence based real-time quantitative PCR (QPCR) measurements of microcystin synthetase gene equivalents (Adj. R2 = 0.85, p < 0.0001). Overall, the lake wide composition of Microcystis spp. was highly variable over time and space, and on average consisted of 36 ± 12% potentially toxic cells. The possibility that nutrient reduction strategies in Taihu may shift the cyanobacterial community toward toxigenic diazotrophic (N2-fixing) genera is discussed. Based on this study‟s findings, a framework for the design and implementation of a water safety plan for Taihu water quality managers and public health officials was proposed.
- Date of publication
- August 2012
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- In Copyright
- Advisor
- Paerl, Hans W.
- Degree
- Doctor of Philosophy
- Graduation year
- 2012
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