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Understanding the occurrence of cyanobacteria and cyanotoxins
Published in Ingrid Chorus, Martin Welker, Toxic Cyanobacteria in Water, 2021
Bastiaan W. Ibelings, Rainer Kurmayer, Sandra M. F. O. Azevedo, Susanna A. Wood, Ingrid Chorus, Martin Welker
A number of cyanobacteria produce specific resting cells called akinetes that sink to the sediment where they can survive for extended periods of time (see Chapter 3). These include, in particular, the N2-fixing taxa Anabaena, Dolichospermum, Aphanizomenon and Raphidiopsis. Recruitment and germination of akinetes from the sediment contributes to bloom onset, and prolonged benthic recruitment may strongly promote the presence of respective species (Karlsson‐Elfgren et al., 2003). Several factors, especially light and temperature, determine their germination (Karlsson-Elfgren et al., 2004; Wiedner et al., 2007). Cirés et al. (2013) show how blooms of Dolichospermum circinale and D. flosaquae are both initiated and maintained in the Murray River (Australia) by the germination of akinetes that are present in the sediment, although vegetative cells also overwinter in the water.
Marked blue discoloration of late winter ice and water due to autumn blooms of cyanobacteria
Published in Lake and Reservoir Management, 2022
Heather A. Haig, Amir M. Chegoonian, John-Mark Davies, Deirdre Bateson, Peter R. Leavitt
Interactions between unprecedented rates of atmospheric warming and excessive nutrient influx have created conditions in which surface waters may experience novel conditions that cannot be anticipated from extrapolation of antecedent environments, a phenomenon known as “ecological surprises” (Christensen et al. 2006, Filbee-Dexter et al. 2017). Here we used analysis of in situ pigmentation from phytoplankton and remote sensing to document the first widespread and marked blue discoloration of nearshore ice and lake water in late winter and early spring. Analyses suggest that this new phenomenon arose when exceptional late fall blooms of Aphanizomenon flos-aquae were trapped in rapidly forming littoral ice, frozen, and released water-soluble C-phycocyanin. Such late blooms of Aphanizomenon spp. are becoming more common in highly eutrophic lakes (e.g., Wejnerowski et al. 2018, Shcherbak et al. 2019), possibly reflecting changes in fall heat waves in lakes (Woolway et al. 2021), which favor continued growth of warmwater taxa (Hayes et al. 2019). Further, as late fall littoral blooms had high levels of Aphanizomenon akinetes (Figure 3d), and this species colonizes the water column from littoral deposits of akinetes, this warming may initiate a feedback loop to favor earlier and more profound cyanobacterial outbreaks, as has been documented recently for these lakes (Hayes et al. 2019). Given that toxic blooms are common in the Canadian Prairies (Orihel et al. 2012, Hayes et al. 2019) and regional climate is forecast to warm by ∼5 C by 2050, particularly during the colder seasons (Sauchyn et al. 2020), autumnal blooms and late winter blue discoloration may become much more common.