Historically cyanobacterial populations in the Fitzroy River system, Central Queensland, Australia have been dominated by Dolichospermum circinale, Sphaerospermopsis spp. and Cylindrospermopsis raciborskii. However, the latter species has been more prevalent in years without major flooding (and higher water temperatures) whereas D. circinale, Sphaerospermopsis, Chrysosporum ovalisporum, and Limnothrix redekei have been more common in years with major flooding (lower water temperatures and higher conductivity).
Following flooding in 2013, cyanobacterial populations were studied in the Isaac River, a northern, inland tributary of the Fitzroy River. The Isaac begins in Lake Elphinstone, a natural lake inland from the city of Mackay. Conditions in the river are extreme in terms of both flow and temperature. Floods can be followed by water depths of less than 30 cm approximately two weeks later. This river flows through the middle of the Bowen Basin and extensive grazing land.
Cyanobacterial populations in Lake Elphinstone have historically been dominated by C. ovalisporum, C. raciborskii and Microcystis panniformis. Blooms of C. raciborskii were once common in deeper sections of the river and man-made impoundments downstream. In contrast, the water column following flooding in 2013 was dominated by Sphaerospermopsis spp., C. ovalisporum, L. redekei and also Dolichospermum smithii in deeper pools with larger nutrient inputs from cattle and wild pigs. Such assemblages represent a change from the Cylindrospermopsis of drier years. Late wet season samples were dominated by eukaryotic algae with only a trace of Limnothrix present.
The assemblages found in Central Queensland are also common throughout eastern Australia. However, unlike the blooms of C. ovalisporum in the Murray system, the Central Queensland strains are toxigenic and produce cylindrospermopsin.