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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
In freshwater, the dominant cyanobacterial taxa in the mats are usually filamentous Oscillatoriales, including Oscillatoria, Microcoleus, Phormidium, Microseira, Moorea (formerly Lyngbya), Leptolyngbya, Tychonema, Calothrix and Schizothrix. The Chroococcales Aphanothece and Synechococcus are also common components of the mats, with some reports of mats dominated by these genera, for example, in hot spring environments. Among the nitrogen-fixing Nostocales, the most frequently reported genera are Anabaena, Scytonema and Nostoc (Quiblier et al., 2013, Wood et al., 2020). Although dominated by cyanobacteria, the mats usually contain many other organisms (e.g., heterotrophic bacteria and eukaryotic algae) and inorganic matter (e.g., sediment) bound together by extracellular polymeric substances (McAllister et al., 2016). Over 20 species of benthic cyanobacteria are known to produce a range of cyanotoxins, similarly wide as that of planktonic species, that is, MCs, nodularins, CYNs, saxitoxins and anatoxins. Toxicity that could not be attributed to any of the known cyanotoxins has also been identified (Quiblier et al., 2013). As in planktonic cyanobacteria, both toxic and nontoxic genotypes of a given species usually coexist within mats (Cadel-Six et al., 2007) and cyanotoxin content can be highly variable spatially and temporally. Little is known about factors which may upregulate toxin production or promote the dominance of toxic over nontoxic strains. However, again as for the planktonic cyanobacteria, the abundance of toxic genotypes appears to be the key contributor to toxin content variability among benthic cyanobacterial-dominated mats (Wood & Puddick, 2017).
Cyanobacterial blooms in Ontario, Canada: continued increase in reports through the 21st century
Published in Lake and Reservoir Management, 2023
Elizabeth J. Favot, Claire Holeton, Anna M. DeSellas, Andrew M. Paterson
An analysis of this provincial algal bloom dataset in 2011 documented a significant increase in the number of government-confirmed public reports of algal and cyanobacterial blooms between 1994 and 2009 (Winter et al. 2011). Its findings indicated that most of the increase in the number of cyanobacterial bloom reports was accounted for from lakes on the Precambrian Shield, and that the most common taxa of cyanobacteria identified in reported blooms were Anabaena (some taxa now reclassified into Dolichospermum), Aphanizomenon, Microcystis, Gloeotrichia, and various Oscillatoriales (Winter et al. 2011). Winter et al. (2011) also noted that algal blooms were being reported significantly later into the fall in the early 2000s than they were during the 1990s. We provide an update on the cyanobacterial bloom portion of this dataset a decade later to determine (1) whether there has been a continued increase in the number of cyanobacterial bloom reports and (2) whether patterns exist in the occurrence of cyanobacterial blooms geographically, seasonally, or with respect to their taxonomic composition and waterbody chemical characteristics. Cyanobacterial toxin data collected as a part of this program are beyond the scope of this article.