Characterisation of Cyanobacterial Bloom Composition and Toxin Production, and its Control using Bismuth Oxide Photocatalytic Material

Jenkinson, Lauren Amy (2025) Characterisation of Cyanobacterial Bloom Composition and Toxin Production, and its Control using Bismuth Oxide Photocatalytic Material. Masters by Research thesis (MSc), Manchester Metropolitan University.

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Abstract

Eutrophication of water bodies is becoming an increasing global problem. The addition of nutrients, like nitrogen and phosphorus, stimulate an overgrowth of algae and the creation of Harmful Algal Blooms (HAB). HABs have been evidenced to produce many detrimental effects and can contain cyanobacteria that produce toxins, which have been shown to cause illness and mortality in wildlife and humans. This study characterised algal blooms in two water bodies known to experience HABs - Rostherne Mere and Tatton Mere. Nutrient levels (PO43-, NO3 and other ions), cyanobacterial populations (visual counts, Chl-a, 16S sequencing, toxin (microcystin) levels (via ELISA) and the presence of genes coding for the production of microcystin). Results from water quality and population analysis indicated an algal bloom formed and was most likely a cyanobacterial bloom. The trophic status of both lakes were classified as eutrophic. 16s rRNA sequencing displayed the bacterial communities within the lakes and cyanobacteria was confirmed at both sites, Sanger sequencing identified Anabaena sp. to be the bloom-forming cyanobacteria at Tatton Mere. Genetic analysis of the microcystin producing gene (mcyE) showed the cyanobacteria present in both lakes had the ability to produce microcystins, in addition ELISA testing of microcystins at both sites revealed that there was microcystins present in the water column at the time of sampling. The ability of the photocatalytic material bismuth oxide (BiOx) to treat the harmful consequences of HABs (cyanobacterial growth and toxin presence) was studied, which was found to be an effective material to inhibit cyanobacterial growth of Anabaena sp. Evidence suggested that the pre-emptive addition of BiOx gave a greater reduction in algal growth. Similarly, BiOx was found to successfully degrade microcystins, with an increasing effect in higher BiOx concentrations. The study has characterised algal blooms using a range of techniques and demonstrated that BiOx has the potential to be a powerful tool for the water industry as an affordable water treatment that could save many lives.