Faecal indicator bacteria monitoring in blue-green algae contaminated water
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Abstract Due to enhanced human and climatically-driven environmental changes, numerous water bodies including the Great Lakes area have seen increased harmful algal blooms (HABs) (including those caused by blue-green algae) in the past few decades. HABs affect the ecological integrity of the affected water by disrupting or altering the biological communities, bringing more challenges to water-quality monitoring and sustainable water management. Faecal indicator bacteria (FIB) monitoring for detection of possible microbial and pathogen contamination is a significant water-management practice, with implications for water resource sustainability. Work in this thesis focuses on HAB impact on faecal indicator bacteria survival and thus the use of FIB for indicating microbial contamination. To serve this purpose, microcosms that contain the representative algae and indicator bacteria were established to explore the algae-bacteria dynamics at laboratory scale. Two species of Microcystis (M. smithii and M. aeruginosa) and four lab strains of E. coli (ATCC 25922, 8739, 51813, and 11775) were used. The sample water was collected regularly for Microcystis and E. coli screening. Microcystis was shown to dramatically reduce E. coli survival in the microcosms. Three possible factors contributing to the observed algae-E. coli dynamics, nutrient (nitrogen and phosphorus) availability, water pH, and microcystin production by Microcystis, were examined; microcystin production was the only factor found to be able to linked to E. coli death. Lastly, lake strains of E. coli and Total coliforms sampled from Lake Ontario were included and showed the same general behavior. The results show that use of FIB (E. coli and Total coliforms) as indicators of faecal contamination in water with Microcystis spp. (and possibly other blue-green algae) present could be greatly compromised, especially if algal toxin is produced. On the other hand, FIB survival dynamics, if interpreted properly, might be used to detect the onset of toxin-producing harmful algal blooms.