Proliferation and anatoxin production of benthic cyanobacteria associated with canine mortalities along a stream-lake continuum.

Proliferations of benthic cyanobacteria are increasingly in the public eye, with rising animal deaths associated with benthic rather than planktonic blooms. In early June 2021, two dogs died after consuming material on the shore of Shubenacadie Grand Lake, Nova Scotia. Preliminary investigations indicated anatoxins produced by benthic cyanobacterial mats were responsible for the deaths. In this study, we monitored the growth of a toxic benthic cyanobacterial species (Microcoleus sp.) along a stream-lake continuum where the canine poisonings occurred. We found that the species was able to proliferate in both lentic and lotic environments, but temporal growth dynamics and the predominant sub-species were influenced by habitat type, and differed with hydrodynamic setting, nutrient and sunlight availability. Toxin concentration was greatest in cyanobacterial mats growing in the oligotrophic lakeshore environment (maximum measured total anatoxins (ATXs) >20 mg·kg-1 wet weight). This corresponded with a shift in the profile of ATX analogues, which also indicated changing sub-species dominance along the stream-lake transition.

Photosynthetic conversion of carbon dioxide from cement production to microalgae biomass.

Production of microalgae is a potential technology for capturing and recycling carbon dioxide from cement kiln emissions. In this study, a process of selecting a suitable strain that would effectively utilize carbon dioxide and generate biomass was investigated. A down-selection screening method was applied to 28 strains isolated from the area surrounding a commercial cement plant. In laboratory-scale (1 L) continuous-mode chemostats, observed productivity was > 0.9 g L-1 d-1 for most strains studied. Chlorella sorokiniana (strain SMC-14M) appeared to be the most tolerant to cement kiln gas emissions in situ, delivered under control of a pH-stat system, and was down-selected to further investigate growth and biomass production at large-scale (1000 L) cultivation. Results demonstrated little variability in lipid, crude protein, and carbohydrate composition throughout growth between kiln-gas grown algal biomass and biomass produced with laboratory grade CO2. The growth rate at which the maximum quantity of CO2 from the emissions is recycled also produced the maximum amount of the targeted biomass components to increase commercial value of the biomass. An accumulation of some heavy metals throughout its growth demonstrates the necessity to monitor the biomass cultivated with industrial flue gases and to carefully consider the potential applications for this biomass; despite its other attractive nutritional properties. KEY POINTS: • Studied high biomass producing algal strains grown on CO2 from cement flue gas. • Chlorella sorokiniana SMC-14M grew well at large scale, in situ on cement flue gas. • Demonstrated the resulting commercial potential of the cultured algal biomass.