Water Research Australia Water for the wellbeing of all Australians March 2015 Page 1

Fact Sheet Blue-green algae (cyanobacteria): a guide

WHAT ARE THEY?

Despite their name, blue-green algae are actually photo- syntheti c bacteria, also called ‘cyanobacteria’, that rely on sunlight for energy.

Blue-green algae are present in almost all aquati c ecosystems, including creeks, rivers, lakes and wetlands. Individual cells are very small, so blue-green algae can be present in a water body without being visible.

As environmental conditi ons become favourable, algae numbers start to increase rapidly,or “bloom”, and scums may become easily visible on the water surface. Blooms range in colour from dark green to yellowish-brown and develop a paint-like consistency as they dry out at the water’s edge. A blue pigment may also be seen as they dry.

A BIG PROBLEM

Algal blooms can cause major problems. Some species of blue-green algae produce chemical compounds that taint drinking water with musty or earthy tastes and odours. These off -tastes and odours are not hazardous to health but require extensive treatment to remove, and in severe cases make the water undrinkable. This can place signifi cant strain on the water supply system.

More signifi cantly, some species produce toxins that can be hazardous to animals and people if they are consumed, inhaled or possibly contact the skin.

Blue-green algal toxins are colourless, odourless, and can remain present in the water weeks after the blue-green algae have disappeared. They are

not destroyed by boiling a� ected water.

With an unsightly appearance and oft en also a pungent smell, cyanobacteria can make aff ected water unappealing for recreati onal acti viti es, such as swimming, boati ng or fi shing. Water aff ected by a bloom is unsuitable for agricultural use.

When blooms form in drinking water storages, such as reservoirs or dams, they can cause serious diffi culti es for drinking water suppliers.

Algal bloom on Murray near Robinvale 2009 (photo courtesy of Vanora Mulvenna)

HIGHLY TOXIC

Blue-green algae produce toxins that can aff ect us in three main ways:

• Hepatotoxins damage the liver and may also increase the risk of certain types of cancer.

• Neurotoxins damage nerves and at high doses can cause numbness and muscle tremors, especially in the muscles animals and people need to breathe.

• Allergens are thought to produce a range of reacti ons in sensiti ve individuals including skin rashes, irritati on of the eyes, and possibly gastroenteriti s.

Although human poisoning and illness from exposure to these toxins is rare, it can be severe and even fatal. The only documented case of human deaths occurred in 1996 in Brazil, where 75 dialysis pati ents died aft er direct exposure to

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toxins in their dialysis fl uid. However, 140 people (from Palm Island, Australia in 1979) were hospitalised aft er drinking water from the local reservoir which had a bloom.

NOT NEW

Algal blooms are not a new phenomenon.

The fi rst scienti fi cally documented case of an algal bloom causing deaths was in South Australia’s Lake Alexandrina in 1878, where catt le, pigs and sheep died within hours of drinking contaminated water.

Algal blooms can cover large areas of a water body and may last for weeks. One of the largest algal blooms ever recorded in a river covered almost 1000 kilometres of the Barwon and Darling Rivers in November 1991. For nearly three weeks, river water was unsuitable for watering livestock, and the people who relied on the river for drinking water had to fi nd other sources. A state emergency was declared and the army was called in to supply potable water. Nearly twenty years later, in 2009, another bloom along the Murray River was esti mated to be 1100 kilometres long.

Research by the Murray-Darling Freshwater Research Centre has shown that while frequency of blooms remains in the range of one to four annually, the durati on and extent of blooms has been increasing in the Murray River since the 1970s. This change has been linked to greater eutrophicati on (enrichment of water with nutrients) from human populati on growth and associated acti vity.

The WaterRA ‘Cyanosurvey’ project, completed in 2013, found that the toxic species are ubiqitous, and can bloom unexpectedly when conditi ons change.

HOW BLOOMS FORM

Like all photosyntheti c organisms, blue-green algae rely on sunlight for energy, with their growth rate determined by environmental conditi ons such as temperature, light availability and nutrients.

Most bloom-forming blue-green algae have pockets of gas (called vacuoles or vesicles), that control their buoyancy.

At the surface,the algae convert sunlight to carbohydrate to build up their energy stores, which eventually makes them heavier and they slowly sink to where the water is higher in nutrients. As they use up their carbohydrate stores, they become lighter and start to rise to the surface again.

The ability to verti cally migrate within the water column can give blue-green algae an advantage over the other micro-organisms, however this is lost when the water becomes turbulent. The gas pockets cannot keep them afl oat in a turbulent water column, reducing the growth rate of the populati on.

There are some excepti ons to this. For instance, some species of blue-green algae do not form surface blooms and can be found concentrated down to depths of 20 metres.

Turbulence and nutrients are the most important factors in determining whether a bloom will form. Waters that fl ow slowly, with low turbulence – such as regulated rivers, dams, or water storages – are at parti cularly high risk of algal blooms.

Nutrient levels do not usually trigger a bloom, but they determine how large it becomes and how long it lasts. Recent work has also shown that micronutrients, such as iron, probably play a role in determining how toxic a bloom will be.

Blooms are likely to form when:

• The water is relatively still

• Nutrient levels are high

• Temperatures remain warm.

Infra-red aerial photography image of Milang, Lake Alexandrina, 1990(photo courtesy of SA Water)

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Most blooms do not last long, oft en disappearing within days or weeks. However, when conditi ons remain favourable, blooms can last months, especially if nutrient levels are high.

TESTING AND MONITORING

Although most surface blooms are obvious to the naked eye, blue-green algae can be present in the water without a visible bloom. There is ongoing research at CSIRO to investi gate the use of sensors and satellite images to detect algal blooms.

At present, to fi nd out whether blue-green algae are present, how concentrated they are, and whether they are potenti ally toxic, experienced laboratory technicians assess water samples using high-powered microscopes.

Once they have confi rmed that blue-green algae are present, additi onal tests, like bioassays or chemical analyses, are used to fi nd out whether they are toxic. This process can take days and can someti mes delay control acti ons.

To speed up the process and help water resource managers respond to outbreaks more quickly, researchers are developing faster tools. Geneti c techniques based on PCR (polymerase chain reacti on) can rapidly identi fy toxic blue-green algae strains within hours, using DNA fl ags to detect

toxin-producing genes.

Field tools, such as dip sti ck test kits, are now available for the most common toxins, and give an immediate result.

GUIDELINES FOR SAFETY

The Commonwealth Government’s Nati onal Health and Medical Research Council (NHMRC) produces the Australian Drinking Water Guidelines to provide advice to water suppliers.

htt p://www.nhmrc.gov.au/_fi les_nhmrc/publicati ons/att achments/eh52_australian_drinking_water_guidelines_150108.pdf

The Guidelines recommend safe limits for various compounds found in drinking water, including blue-green algal toxins.

They also contain fact sheets that give informati on about blue-green algal toxins, including a summary of the current knowledge on the health signifi cance, management and water treatment of the chemical classes of blue-green algal toxins encountered in Australia.

Because blue-green algae can be toxic on contact, not just when consumed, the hazards they pose in recreati onal waters should be assessed by health authoriti es on a case-by-case basis. Any contact with bloom aff ected water should be avoided. Guidelines have also been developed by the NHMRC for acceptable levels of exposure to cyanobacteria in water used for recreati on. htt p://www.nhmrc.gov.au/_fi les_nhmrc/publicati ons/att achments/eh38.pdf

PREVENTING AND CONTROLLING ALGAL BLOOMS

Blue-green algal blooms are a natural part of the aquati c environment. As it is likely that water resource managers will never be able to completely prevent algal blooms, research and management of blue-green algae emphasises control and treatment in important water supplies.

A number of strategies are recommended to avoid or manage blooms, including:

• Physical controls, such as arti fi cially mixing the water column to create turbulence and break down thermal strati fi cati on

• Minimising nutrient levels in water storages

• Restricti ng light onto the water surface. For instance, covering tanks or dams

• Taking water from diff erent parts of the reservoir

• Chemical controls, such as algicides

Treatment of blooms is complicated by the fact that as cells die and begin to break down, taste and odour compounds and toxins are released into the water. Cells may also release toxins as they grow. Water resource managers need to be

Blue-green algae cultures from 2012 national survey (photo courtesy of SA Water)

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aware that any control method that causes the cells to burst (for instance, the applicati on of algicides, or chlorinati on) can cause toxins to be released into the water, in some cases then making them harder to treat.

TREATING BLOOMING WATER

Modern treatment technology is highly eff ecti ve at making water aff ected by blooms safe to drink.

When processing water aff ected by algal blooms, treatment plant operators will adjust their normal regime so that they remove algal cells, off -tastes and odours and toxins. They use a combinati on of fl occulati on, fi ltrati on, acti vated carbon and chlorinati on.

In some cases, water suppliers will stop taking water from a storage aff ected by a bloom when alternati ves are available.

WHAT NEXT?

Water Research Australia (and previously the CRC for Water Quality and Treatment), with funding and support from the Australian water industry and many Australian universiti es have undertaken an extensive research program on many aspects of understanding and managing algal blooms. Projects have included:

• developing methods to rapidly measure algal toxins in drinking water

• investi gati ng water treatment methods for removal, and

• controlling cyanobacterial blooms in both reservoirs and rivers

Research has also focussed on health eff ects of cyanobacteria to allow for the development of bett er guidelines for both drinking and recreati onal waters.

Cyanobacterial researchers from Australia and New Zealand have been meeti ng every two years to discuss their projects and new developments in bloom management, knowledge

about species and ecology and treatment technology. Many of the presentati ons can be viewed on the WaterRA website.

htt p://www.waterra.com.au/events/events/nati onal-cyanobacterial-workshops/

COMMON SENSE TIPS• Do not drink untreated water, whether you

can see a bloom on the surface or not. As well as presenti ng possible health risks from algal blooms, untreated water can cause other illnesses.

• Musty or earthy odours - that are not normally present in your drinking water - may indicate algae in the source water. If you are unsure about the water quality, and suspect cyanobacteria may be responsible, call your local water authority.

• Boiling aff ected water does not destroy blue-green algae toxins.

• Authoriti es will oft en use signage in parks and on river banks to alert the community about blooms or other hazards (such as polluted stormwater).

• Do not swim in water containing visible blooms.

• If blooms are present, do not let livestock or pets drink or swim in the aff ected water. Use alternati ve sources of drinking water.

For more informati on, visit the website: www.waterra.com.au

Further reading:

Francis G (1878) Poisonous Australian lake. Nature, 2 May, 11-12.

Hobson P, et al (2010) Tastes and odours in reservoirs. WQRA Research Report No 73.

Newcombe G, et al (2010) Management of Cyanobacteria, a Guide for Water Uti liti es. WQRA Research Report No.74.

Research into cyanobacteria and their metabolites has produced wide-ranging

bene� ts for the Australian water industry, the environment and the public, through

improved knowledge about blooms, cyanobacterial species and occurrence, managing the risks to water and human

health and optimising operations at treatment plants.

COMMON SENSE TIPS• Do not drink untreated water, whether you Do not drink untreated water, whether you

can see a bloom on the surface or not. As well can see a bloom on the surface or not. As well as presenti ng possible health risks from algal as presenti ng possible health risks from algal blooms, untreated water can cause other blooms, untreated water can cause other illnesses.illnesses.

• • Musty or earthy odours - that are not normally Musty or earthy odours - that are not normally present in your drinking water - may indicate algae in the source water. If you are unsure about the water quality, and suspect cyanobacteria may be responsible, call your local water authority.

• Boiling aff ected water does not destroy blue-green algae toxins.

• Authoriti es will oft en use signage in parks and on river banks to alert the community about blooms or other hazards (such as polluted stormwater).

• Do not swim in water containing visible blooms.

• If blooms are present, do not let livestock or pets drink or swim in the aff ected water. Use alternati ve sources of drinking water.

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