The Occurrence of Toxic Cyanophyte Blooms in Australia

Abstract

Australian literature records stock losses due to excessive growths in water of the cyanophyte algae Anaeystis cyanea (Küetz.) Dr. and Dail. (= Microcystis aeruginosa Küetz.), Anabaina circinalis Rabenh. and Nodularia spumigena Mert. (now Nostoc spumigena (Mert.) Drouet). These algal species were recorded in Australia at least sixty years ago, but their increasing occurrence, wide distribution and the resultant damage appear to be due to increasing pollution of the water.

Factors affecting the toxicity of these blue-green algae are discussed. Animals affected adversely include horses, cows, sheep, dogs, pigs, fowls, turkeys, laboratory guinea pigs, mice and probably various wild animals, including birds and fish.

Particular attention is given to Anabaina circinalis, its nomenclature, ease of distribution and factors affecting its establishment and growth. It appears that a series of physiological abilities in the group of blue-green algae allows these plants to take advantage of conditions prevailing under eutrophic or drought conditions, and so to outgrow green algae.

Control of the concentration of phosphorus appears to be the most practical method of controlling the occurrence of these blooms. My work indicated that blooms only developed when phosphorus levels reached a concentration of 0.5 ppm, and that at these times there was a high bacterial count which no doubt aided the freeing of phosphorus from the previously-enriched sediment.

Treatment of farm dams with alum and/or block ferric alum (Alumina ferric R), applied before the summer rise in phosphorus levels, limited this rise and reduced or inhibited cyanophyte bloom formation.