Toxic algal blooms – a sign of rivers under stress
Box 3 | Harmful effects of blue-green algae on human health
This is an extract of a paper by Ian Falconer published in Australian Biologist, 1997, vol. 1, no. 2, pages 107-110. It is reproduced here with the permission of the author and the publisher.
Varieties of blue-green algae
Blooms of blue-green algae frequently occur in recreational lakes and rivers used for water sports during the summer swimming season. Swimmers have even been seen playing in the green scum, and having their photographs taken with streaks of green over their bodies. (One group of British Army recruits, unfortunately for them, were given a day of swimming in full packs, and doing eskimo rolls in canoes as part of their training, in a lake with a toxic bloom of Microcystis. This is a particularly nasty toxic variety of blue-green algae, and the soldiers developed blisters on their mouths, and suffered vomiting, diarrhoea, very sore eyes and in two cases, acute pneumonia).
The blue-green alga, Microcystis, occurs widely in Australia, and has caused many cases of livestock poisoning in New South Wales and Victoria. The other common blue-green alga in the rivers and lakes of the Murray-Darling Basin is the species Anabaena circinalis, which was the cause of the big Darling River bloom in 1990-91. Many sheep and cattle died along the river, and samples of the alga from the water have since been found to contain the same paralytic poisons that are present in poisonous shellfish.
Another poisonous blue-green alga prefers warmer water and is more abundant in Queensland. It is usually a straight filament of cells, which contrasts with the Anabaena species which is tightly curled, and Microcystis, which forms a sponge-like blob. This tropical alga, Cylindrospermopsis, is found in rivers, reservoirs and freshwater billabongs. Unlike Microcystis and Anabaena, Cylindrospermopsis does not form surface scums where concentrated cells can be drunk by livestock. However, algal cell densities may be very high, in the hundreds of thousands per millilitre, and located in a band several metres from the surface in a reservoir. This makes the alga a more difficult problem in a drinking water supply, as water is normally drawn from several metres depth in the deeper part of a reservoir.
In the 1970s, Cylindrospermopsis seasonally occurred in Solomon Dam, Palm Island, Queensland in large quantities. On one occasion in 1979 the dam was treated by the supply authority with copper sulphate to kill the algae, which in turn released the toxins into the water. A week later about 150 people drinking from that water supply became ill, and many had to be hospitalised. They showed evidence of gastrointestinal, liver and kidney damage, with no evidence of a causative virus or other pathogen.
Recently, research into this toxic blue-green alga has progressed considerably. The harmful actions on animals of the algal toxins from a Palm Island sample have been described, and the poisonous alkaloid which appears largely responsible has been identified. (The mechanism of action is under active investigation in Japan and Australia.) Unfortunately Cylindrospermopsis has been found in several significant drinking water supply reservoirs and rivers in Australia in the last few years as well as lakes and farm dams, so the water authorities here are monitoring the situation with care.
Research
At the Cooperative Research Centre for Water Quality and Treatment in Adelaide' there are two programs of research into blue-green algae. One is focussed on the biology and distribution of toxic algae and their control, and the other focusses on their ill effects on humans. Of particular importance is the potential of some of the algal toxins to stimulate the growth of cancers. This effect has been demonstrated in experimental animals and there is evidence of human cancers associated with drinking contaminated surface water.
It is particularly important to identify the risks to the population arising from this possibility, so that water safety guidelines can be set.
Water quality
The potential for contamination of drinking water by blue-green algal toxins has resulted in the Australian authorities, and the World Health Organization (WHO) setting up working parties to develop water quality guidelines. These will specify 'safe' concentrations of these algal toxins in drinking water. The WHO guidelines are not compulsory, but act as a basis for governments to enact legislation on water quality. They will also provide guidance to public and private water supply authorities on the monitoring and safe concentrations of these toxins in drinking water.
As human populations increase, so will the potential for toxic algal blooms. It is likely that both ecological measures to improve water quality and improved water treatment methods will be needed in the future.
References
Byth, S. 1980, 'Palm Island mystery disease', Med. J. Aust., 2:40-42.
Carmichael, W.W., An, J-S., Azevedo, S.M.F.O., Lau, S., Rinehart, K.L., Jochimsen, E.M., Holmes, C.E.M. & Jarvis, W.R. 1996, 'Analysis for microcystins involved in an outbreak of liver failure and death of humans at a hemodialysis center in Caruaru, Pernambuco Brazil', IV Symposium of the Brazilian Society of Toxinology, October 6-12, Recife, Pernambuco, Brazil.
Falconer, I.R. 1988, 'Eutrophication by toxic blue-green algae. An increasing hazard in Australia', Australian Biologist, 1:10-12.
Falconer, I.R. 1993, ed., Algal toxins in seafood and drinking water, Academic Press, London.
Falconer, I.R. & Humpage, A.R. 1996, 'Tumour promotion by cyanobacterial toxins', Phycologia 35: (6 suppl.) 74-79.
Hawkins, P.R., Chandrasena, M.R., Jones, G.J., Humpage, A.R. & Falconer, I.R. 1997, 'Isolation and toxicity of Cylindrospermopsis raciborskii from an ornamental lake', Toxicon 35 (in press).
Hawkins, P.R. Runnegar, M.T.C., Jackson, A.R.B. & Falconer, I.R. 1985, 'Severe hepatotoxicity caused by the tropical cyanobacterium (blue-green alga) Cylindrospermopsis raciborskii (Woloszynska) Seenaya and Subba Raju isolated from a domestic water supply reservoir', App. Env. Microbiol., 50:1292-5.
Hayman, J. 1992, 'Beyond the Barcoo – probably human tropical cyanobacterial poisoning in outback Australia', Med. J. Aust. 157:794-796.
Humpage, A.R., Rositano, J., Bretag, A.H., Brown, R., Baker, P.D., Nicholson, B.C., & Steffensen, D.A. 1994, 'Paralytic shellfish poisons from Australian cyanobacterial blooms', Aust, J. Mar. Freshwater Res. 45:761-771.
Ohtani, I., Moore, R.E. & Runnegar, M.T.C. 1992, 'Cylindrospermopsin: a potent hepatotoxin from the blue-green alga Cylindrospermopsis raciborskii', J. Am. Chem. Soc. 114:7942-7944.
Turner, P.C., Gammie, A.J., Hollinrake, K. & Codd, G. A. 1990, 'Pneumonia associated with cyanobacteria', Br. Med. J. 300:1440-1441.
Boxes
Box 1. Is Newcastle's water vulnerable to toxic algal blooms?
Box 2. Cyanobacteria: the simple things of life
Related site
Cooperative Research Centre for Water Quality and Treatment
Note: the CRC for Water Quality and Treatment has been succeeded by Water Quality Research Australia Limited.
Page updated February 2012.