Date of Award

2017

Document Type

Open Access Thesis

Department

Marine Science

Sub-Department

College of Arts and Sciences

First Advisor

Dianne I. Greenfield

Abstract

Cyanobacteria are responsible for the largest number of harmful blooms (HABs) worldwide. HABs caused by the genus Microcystis pose public health threats because they often occur within close proximity to humans and produce microcystin (hepatotoxin), which can contaminate drinking water and recreational areas. Novel molecular techniques facilitate monitoring, ‘early warnings’ of HAB events, and appropriate management responses. Sandwich hybridization assay (SHA), the technique considered here, directly (no amplification) identifies and quantifies planktonic species using ribosomal RNA (rRNA)-targeted oligonucleotides. This project developed SHA for Microcystis 16S rRNA and validated the assay using laboratory cultures and samples from a multi-specific cyanobacteria bloom in a coastal stormwater detention pond. The assay calibration curve and limits of detection were determined using M. aeruginosa culture, though interspecific (M. aeruginosa, M. botrys, M. wesenbergii) comparisons revealed significantly (p < 0.05) different responses for a comparable cell density. Assessments of three light intensities (40, 60, 100 µmol photons m-2 s-1) and two temperatures (25, 32˚C) showed that M. aeruginosa SHA response at 25˚C decreased with light intensity, but varied at 32˚C, with a significant (p < 0.05) interaction between light intensity and temperature. A multi-specific cyanobacteria bloom of the genera Anabaena, Anabaenopsis, and Microcystis occurred during summer 2016. Microcystis abundance was not significantly (p > 0.05) correlated with any form of measured nutrients, but was positively and significantly (p < 0.05) correlated with microcystin concentration. The newly developed SHA successfully detected Microcystis from environmental samples, showing its potential for its integration with cyanoHAB monitoring efforts.

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