Lc. Bowling et Pd. Baker, MAJOR CYANOBACTERIAL BLOOM IN THE BARWON-DARLING RIVER, AUSTRALIA, IN1991, AND UNDERLYING LIMNOLOGICAL CONDITIONS, Marine and freshwater research, 47(4), 1996, pp. 643-657
The occurrence of a severe cyanobacterial bloom is described. This blo
om affected almost 1000 km of the Barwon-Darling River, New South Wale
s, Australia, in November and December 1991 and was dominated by Anaba
ena circinalis Rabenhorst. This cyanobacterium was present in concentr
ations of around half a million cells per millilitre at some localitie
s during its peak in mid November. Moderate to very high toxicity was
demonstrated by mouse bioassay at many localities during this time. Th
e bloom was attributed to very low flow conditions and high nutrient c
oncentrations, especially of total phosphorus. However, warm water tem
peratures, elevated pH, reduced turbidity, and improved water transpar
ency would also have been contributing factors. Very high ammonia conc
entrations were also observed during the bloom. The bloom declined dur
ing December and was eventually flushed from the river by increased fl
ows following heavy catchment rainfall between mid December and early
January.