Toxic algal blooms – a sign of rivers under stressToxic algal blooms pose a serious threat to Australia's already embattled waterways and are the subject of much scientific research.
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Key textA blooming disaster Australia holds one world record it could do without: in November 1991 we scored the largest river toxic algal bloom in history. An estimated 1000-kilometre stretch of the Barwon and Darling rivers in New South Wales was affected; from the air it looked like a long ribbon of pea soup. But it wasn't so drinkable. Toxic algal blooms are just that: toxic. The government declared a state of emergency as livestock perished and residents who normally took their drinking water from the rivers were forced to rely solely on rainwater tanks and emergency water-filtration equipment. Luckily, the small number of people living in the area meant that this problem was manageable. But imagine if a water supply for a major urban centre was affected by a toxic algal bloom. This is not as unlikely as you may think (Box 1: Is Newcastle's water vulnerable to toxic algal blooms?). What is a toxic algal bloom? Blue-green algae, more correctly known as cyanobacteria, are naturally occurring components of all freshwater environments (Box 2: Cyanobacteria: the simple things of life). They occur as single microscopic cells or in colonies that form slimy strands visible to the naked eye. When conditions are favourable, blue-green algae populations can 'bloom', multiplying at such a rate that they dominate the local aquatic environment. At this point, problems for other organisms start to occur. The water begins to stink and a green scum may appear on the surface. Some species of blue-green algae produce toxins which are dangerous – sometimes fatal – to livestock, wildlife, marine animals and humans. The decomposition of dead blue-green algal cells by bacteria consumes oxygen. When billions of such cells die during a bloom, the water becomes oxygen-depleted. This can lead to the death of other marine organisms, including fish, which need oxygen to survive. As well, the blue-green algae contain toxins that affect human and animal health (Box 3: Harmful effects of blue-green algae on human health). A fair-dinkum problem Toxic algal blooms are not unique to Australia. They have been reported in many different river, lake and estuarine systems throughout the world. Nevertheless, the problem is particularly acute in Australia: current land and water management practices combine with our generally arid climate to create conditions in which blue-green algae thrive. First, blue-green algae like abundant phosphorus and nitrogen. These two nutrients enter Australia's waterways in large amounts from factories and sewerage outlets, and as run-off from farms and suburban parks and lawns. This process is known as eutrophication. Much of the phosphorus and nitrogen comes from ordinary household detergents. Blue-green algae are favoured by long periods of sunlight which provide warm temperatures and the energy for photosynthesis. Sunlight is rarely in short supply in Australia. They also enjoy still, calm conditions. Such conditions are usually present in dams and reservoirs, but they can also occur in rivers during drought or when their flow is reduced by irrigation and household use. The flow of many river systems in Australia can sometimes be too low to prevent algal blooms. When an ecosystem is functioning properly, population explosions can often be kept in check by natural processes. For example, many aquatic animals feed on blue-green algae. But Australia's aquatic ecosystems have been affected by such things as the damming of rivers and the introduction of pests like European carp. A damaged ecosystem may be less able to cope with the effects of algal blooms. Watering down the resource Toxic algal blooms are symptomatic of a broader land and water management problem in Australia. Although our waterways are our most precious resource, for decades we have been using them as a waste disposal unit. At the same time, exotic pests have invaded almost every pond, dams and drainage systems have altered natural flow patterns, and river banks have become severely eroded. Can the problem be solved? Science can certainly help. We are still learning, but already scientists have developed techniques to help deal with the toxic algal blooms. Research into the primary sources of excess phosphorus and nitrogen in our waterways has led to the development of improved land management practices. The detergent industry has also reduced the amount of phosphorus in its products. Stirred, not shaken Other techniques to minimise algal blooms have been surfacing. For example, a team led by CSIRO's Dr Ian Webster has discovered that blue-green algal blooms can be reduced by 'stirring'. During calm, sunny periods, a warm surface layer develops in water-bodies. This effect is known as 'thermal stratification'. An experiment conducted by Dr Webster and his team showed that thermal stratification was the key factor in the establishment of blue-green algal blooms: the blue-green algae floated up to this warm layer where they absorbed light and bred rapidly. The team concluded that if thermal stratification could be minimised by mixing the cold and warm layers, blue-green algal blooms might be prevented. But how can big dams be 'stirred'? Different techniques include increasing 'environmental flows' from dams and releasing water in 'pulses' rather than at a steady rate. Don't bank on our rivers Another research effort led by Professor Bob Wasson at the Australian National University has discovered that river bank erosion is a much more significant contributor to the sedimentation of our waterways than was previously thought. Erosion, in turn, brings phosphorus into the waterways, thereby helping to create favourable conditions for blue-green algae. Such erosion could be prevented by some simple, though sometimes costly, land management practices. These include fencing off rivers, providing alternative watering points for livestock away from river banks, and revegetating small channels and gullies. More than science is required Scientists will not solve the problem by themselves. Restoring our waterways will take a concerted effort by all Australians. We need to implement land and water management practices that treat our arid continent more sympathetically. We also need to reduce our water consumption and the rate at which we dump phosphorus, nitrogen and other wastes into rivers, lakes and streams. Coordinated efforts along these lines are already underway. Perhaps most importantly, we need to learn how to live with our environment, not against it. World records for environmental disasters? Gold medals aren't given out for those.
Another source is the Grahamstown Reservoir, which is filled largely by water taken from the Seaham Weir on the lower Williams River. This reservoir supplies about 60 per cent of the water consumed in the cities of Newcastle and Lake Macquarie. The Williams River recorded blue-green algae blooms in three consecutive summers between 1991 and 1993. Grahamstown Reservoir also experienced a bloom in February 1992. While these outbreaks did not pose an immediate health risk to people, they provided a warning that the region's water supply is vulnerable to toxic algal blooms. Emergency measures Land and water managers in the Hunter Valley have taken several steps to limit the impact of toxic algal blooms. One important measure is water monitoring. The presence of potentially toxic blue-green algae species in the Newcastle water supply is monitored on a weekly basis at Grahamstown Reservoir and Chichester Dam and fortnightly in Williams River. A contingency plan has been prepared in the event that an abnormal level of potentially toxic blue-green algal cells is detected. Water from the Grahamstown Reservoir will be filtered by a substance known as granulated activated carbon, which will remove toxins. If necessary, the Grahamstown Reservoir will be taken off-line and substituted by water from a subterranean supply. At extremely high levels of blue-green algal cells, the reservoir will be closed to recreational use. Prevention is better than cure While such measures are necessary to protect the Newcastle water supply in an emergency, they address the symptoms, not the causes, of toxic algal blooms. Longer term options must also be pursued to reduce the risk of blooms occurring in the first place. Perhaps the main reason that the Williams River and Grahamstown Reservoir are vulnerable to algal blooms is the way in which the land and water are managed in the catchment area. The Williams River flows through agricultural and pastoral areas and through several rural townships. Farm run-off and township effluent are major sources of phosphorus which, when present in the river at sufficient concentrations, can lead to a toxic algal bloom. In a recent inquiry into the health of the Williams River, the NSW Healthy Rivers Commission recommended that a number of actions be taken to ensure the continued health of the river system. These included the fencing of streams to prevent trampling by animals, the rehabilitation of banks and streams, and limits on water use. The Williams River Total Catchment Management Committee is working with water users, farmers, government agencies and industry throughout the catchment to help bring about improvements in the way we use both the land and the water. Hopefully, a cooperative approach will ensure that the region's water remains good enough to drink. Related site
They are with us still. Indeed, blue-green algal blooms are becoming increasingly more evident in Australia's rivers and lakes as human activities create conditions in which they thrive. Bacteria are characterised by prokaryotic cells Cyanobacteria are 'prokaryotic' life forms, which simply means that the genetic material in their cells is not enclosed by a membrane. This characteristic is distinctive of bacterial cells; all other cells (eukaryotic) have their genetic material contained inside a membrane. Bacteria are hardy creatures Bacteria can survive in hot, cold, salty, acidic and alkaline environments in which eukaryotes would perish. They have a bad image: after all, they cause many diseases in humans, some of them fatal. Yet, without them we might not be here. Most scientists believe that the earliest life forms were bacteria, simple creatures that fed on carbon compounds that were accumulating in Earth's early oceans. In the harsh conditions that were present then, no other organism could have survived. Other organisms evolved from early bacteria Slowly, other bacteria evolved that could use the sun's energy to manufacture their own food. Cyanobacteria then went a step further: they started to extract hydrogen from water during photosynthesis, releasing oxygen as a by-product. Over time, enough oxygen accumulated in the Earth's atmosphere to allow the evolution of oxygen-using organisms. We could even owe them more than that. Many scientists think that eukaryotic cells may have evolved from prokaryotic cells which 'swallowed' other prokaroytic cells, thus creating membrane-enclosed nuclei. Regardless of how it happened, the creation of eukaryotic cells was a significant milestone in the history of life on Earth. As conditions became more favourable, there was a rapid expansion in biological diversity and the evolution of ever more complex organisms. Two or three billion years later, we have reached a point in our own evolution where we can peer down a microscope at perhaps a thousand of these tiny life forms drifting about in a drop of water. Are we looking at our ancestors? Related site
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. Related site
Materials (for the class)
pond water (source of algae) Procedure
Do this by reading your water meter and recording the reading. Read the meter again 2 days later. If you choose days when you have unusually large water use (eg, days when you water the garden or wash the car), choose similar days for your second reading. Read the meter again at the beginning and end of a 2-day interval. How much water did you save? Roughly how much water could you save by using water sparingly for a year?
List those wastes that should never be poured into these outlets and those which it would be better to use in small quantities. Find out how solvents, oils and other harmful chemicals should be disposed of in your locality.
Australasian Science November/December 2005, page 29-31 Toxic blue-green algae: It's what's on the inside that counts (by Susan White) Describes how algal toxins can accumulate in animals and the implications for managing algal blooms.
October 2002, page 6 Overstocking fish causes toxic blooms (by Stephen Luntz)
Ecos No. 124, 2005, page 34 Growing fuel from algae (by Steve Davidson) Describes research into using microalgae as a future source of renewable biofuels.
No. 120, 2004, pages 32-33 Underground nitrogen busting is crucial (by Wendy Pyper) Looks at the role that waterside habitat plays in reducing the amount of nitrate flowing into waterways, lessening the risk of algal blooms.
No. 115, 2003, page 4 Stocking experiment tests the limits of the lake (by Wendy Pyper) Describes research that has found that overstocking of fish can trigger blue-green algae blooms.
No. 93, 1997, pages 4-5 Toxic algal blooms all in the genes (by Roger Beckmann)
No. 92, 1997, pages 30-33 Griffith gets growing (by Bryony Bennett) Griffith, in NSW, is trialling a new method of irrigating with sewage effluent.
No. 90, 1996-97, page 7 Water quality at risk, scientists warn Agricultural chemicals and algal toxins are water quality issues.
No. 87, 1996, pages 21-25 Don't overfeed the trees Instead of discharging sewage effluent into waterways, a CSIRO project uses it to irrigate tree plantations.
No. 86, 1995-96, page 5 River algae go with the flow (by David Mussared) Environmental flows of rivers affect algal blooms.
New Scientist 16 June 2007, pages 18-19 US set to track toxic algal blooms (by Aria Pearson) Looks at the use of computer simulations to monitor algal blooms.
RTD Info May 2006 The enigma of the blue algae Reports on a European project trying to gain a better understanding of the harmful effects of blue-green algae by looking at the peptides they synthesise.
Scientific American 5 April 2005 Algae found to produce potential neurotoxin (by Sarah Graham)
A general coverage of blue-green algae (cyanobacteria). Explains what they are, how they affect our health and methods of control.
Algal blooms (Water and Rivers Commission, Western Australia)
Presents general information, public health concerns and ecological problems associated with algal blooms (eg, 'What are algae?', 'Health warning' and 'The role of algae in waterways').
CSIROnline Australia
NSW algal information (New South Wales Department of Natural Resources, Australia)
Provides a map of locations experiencing algal blooms and other information about algal blooms.
Waterwatch (Waterwatch Victoria, Australia)
Waterwatch is a national volunteer water quality monitoring program. This site is divided into a number of sections including 'Water fun', which has an interactive habitat survey; and 'For the teacher', which contains manuals on water quality monitoring.
Managing Australia's inland waters (Australian Government Department of Industry, Science and Tourism, Australia)
This paper was prepared for the Prime Minister's Science and Engineering Council's meeting on 13 September 1996. The executive summary presents an overview of the paper. The chapter on agricultural chemicals and algal toxins (17 pages long) is particularly relevant to toxic algal blooms.
The toxic cyanobacteria home page (Purdue University, USA)
Covers different types of cyanobacteria and the kinds of toxins they produce.
Blue green algae: A guide (CRC for Water Quality and Treatment)
A helpful fact sheet about blue green algal blooms.
Waterwatch Australia (Natural Heritage Trust)
The 'Waterwatch library' has a number of publications, including Preparing a Waterwatch action plan and Starting a Waterwatch group.
ecosystem. A term used to encompass all the organisms in a community together with the associated physical environmental factors with which they interact (eg, a rockpool ecosystem, a forest ecosystem). eutrophication. An increase in the nutrient content of a body of water, occurring either naturally or as a result of human activities. It often leads to a rapid increase (bloom) in growth of algae. The death and eventual decomposition of the algae results in a lowering of the oxygen level until the water cannot support organisms that require oxygen. photosynthesis. The biochemical process in which green plants (and some microorganisms) use energy from light to synthesise carbohydrates from carbon dioxide and water.
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