Profile of a bloom of the cyanobacterium Cylindrospermopsis raciborskii (Woloszynska) Seenaya and Subba Raju in the Fitzroy River in tropical Central Queensland

Abstract

The physical, chemical and biotic conditions before and during a bloom of predominantly coiled heterocystous C. raciborskii are described. Initial increases in the population of this species were associated with windy days and the first downward movement of the thermocline into an anoxic hypolimnion after an extended period of stable stratification and no flow. Exponential growth and bloom formation coincided with the amval and retention of first wet-season inflows into the river impoundment. Cyanobacteria and rotifers dominated the planktonic assemblage and chytrids (cyanobacterial pathogens) were present when the cell density of cyanobacteria peaked. Grazing of the coiled forms that dominated during the bloom was not recorded, but the rotifer Brachionus angularis has been observed ingesting entire straight trichomes of C. raciborskii.

Morpho-physiological responses of a subtropical strain of Cylindrospermopsis raciborskii (Cyanobacteria) to different light intensities

“…This finding differs from other results, which reported a more narrow range of optimum light (75 to 125 μmol photons m -2 s -1 ) for strains isolated from a variety of sites (Dyble et al 2006;Bonilla et al 2012;Briand et al 2004). The ability of C. raciborskii to grow faster than other diazotrophic species under high light intensities is an important physiological feature (Fabbro & Duivenvoorden 1996;Briand et al 2004) that enhances their potential threat for water use, particularly in tropical regions.…”

The success of the cyanobacterium Cylindrospermopsis raciborskii in freshwaters is enhanced by the combined effects of light intensity and temperature

“…The species can exploit high light conditions, as found in field (Fabbro and Duivenvoorden, 1996;Dokulil and Mayer, 1996) and experimental studies (Wu et al, 2009;Mehnert et al, 2010). Our analysis showed maximum C. raciborskii dominance of the phytoplankton in both low (z eu /z mix <0.2) and high (z eu /z mix >1) transparency conditions, reinforcing the species' capacity for success in different light environments due to its phenotypic plasticity (Piccini et al, 2011;Mehnert et al, 2012).…”

Cylindrospermopsis raciborskii (Nostocales, Cyanobacteria): A brief historic overview and recent discovery in the Assiniboine River (Canada).

“…The specimens found for the most part had heterocyt so were fixing nitrogen. They were primarily the straight form (there is a high degree of morphological variability (FabbRo et al 1996, komáRek & komáRková 2003 and in the tropics akinetes or resting stages are rare but here immature akinetes were found so if they were successful in completing them it will enable them to over winter in our temperate climates. It has been reported that optimum temperatures for their akinete germination is 22-25°C (FabbRo & duivenvooden 1996) so given the adaptability of the organism it may or may not be able to germinate again in this river.…”