Abstract
Cyanobacterial blooms present challenges for water treatment, especially
in regions like the Canadian prairies where poor water quality
intensifies water treatment issues. Buoyant cyanobacteria that resist
sedimentation present a challenge as water treatment operators attempt
to balance pre-treatment and toxic disinfection by-products. Here, we
used microscopy to identify and describe the evolution of cyanobacterial
species in Buffalo Pound Lake, a key drinking water supply. We used
indicator species analysis to identify temporal grouping structures
throughout two sampling seasons from May to October 2018 and 2019. Our
findings highlight two key cyanobacterial bloom phases – a mid-summer
diazotrophic bloom of Dolichospermum spp. and an autumn Planktothrix
agardhii bloom. Dolichospermum crassa and Woronchinia compacta served as
indicators of the mid-summer and autumn bloom phases, respectively.
Different cyanobacterial metabolites were associated with the distinct
bloom phases in both years: toxic microcystins were associated with the
mid-summer Dolichospermum bloom and some newly monitored cyanopeptides
(anabaenopeptin A and B) with the autumn Planktothrix bloom. Despite
forming a significant proportion of the autumn phytoplankton biomass
(greater than 60%), the Planktothrix bloom had previously not been
detected by sensor or laboratory-derived chlorophyll-a. Our results
demonstrate the power of targeted taxonomic identification of key
species as a tool for managers of bloom-prone systems. Moreover, we
describe an autumn Planktothrix agardhii bloom that has the potential to
disrupt water treatment due to its evasion of detection. Our findings
highlight the importance of identifying this autumn bloom given the
expectation that warmer temperatures and a longer ice-free season will
become the norm.