Blue-Green Algae

The blue-green algae Red/High alert for the Murray River and the Murray Valley Irrigation Area channels is over.

Water users are reminded that all water supplied by G-MW is unfit for any use involving human comsumption, directly or indireclty, without first being properly treated.

Further downgrading of Red alerts in the Murray and Edward Rivers - 9 May 2009

Red alert lifted for parts of the Murray River - update 4 May 2009

Murray River algae alert declines downstream of Echuca - update 17 April 2009

Blue-green Algae - Questions and Answers - 6 April 2009

For algae alerts beyond G-MW's area refer www.lmw.vic.gov.au and www.dwe.nsw.gov.au

Algal bloom outbreaks in natural waterways and channels cause community concern about the nature and effects of these blooms. Farmers have been seeking information on management practices that will lessen the likelihood of them experiencing problems resulting from the presence of algae.

Many of our lakes and waterways have become enriched with nutrients, mainly nitrogen and phosphorous. This may have occurred naturally or as a result of human activities such as farming, urban development and forest clearing. Increasing the nutrient load to the aquatic environment can result in a dramatic increase in the production of algae and other aquatic plants. This can, in turn, lead to a number of significant water quality problems including fish deaths, scums, offensive taste and odours, toxins, corrosion of supply system and tanks, filter clogging, health risks and water treatment problems.

In low numbers, algae are not usually a problem. In fact, they are an essential part of a healthy body of water as they produce oxygen and are themselves a source of food for certain aquatic fauna. Also, some types can convert nitrogen gas into forms that improve the fertility of the water.

Algal blooms in general, and those of potentially toxic blue-green algae (cyanobacteria), can affect water quality by causing peculiar tastes and odours, discolouration and unsightly scums. As the bloom dies, the decaying algal cells reduce the oxygen concentration in the water and produce toxins that can be poisonous to humans and animals.  Under favourable conditions outbreaks of blue-green algae can develop into major blooms, presenting significant health risks to regional communities.

Algae Awareness

Algae, a diverse group of mostly aquatic plants, can be found in both salt water and fresh water. The freshwater forms tend to be small, the vast majority being microscopic, although they often betray their presence by discolouring water. Most algae are harmless to humans and animals but a few are highly toxic, particularly some of the blue-greens which actually resemble bacteria more closely than the true algae.

For convenience, all the freshwater algae can be grouped into four main categories:

  • Flagellates can swim independently and in large numbers can often affect the taste and odour of drinking waters.
  • Diatoms are usually brown or yellow in colour and are mostly free floating, while some types often attach to the stems and leaves of other water plants, coating them with a brown slime.
  • Green algae, which come in all shapes and sizes, are commonly present in reservoirs and dams, rivers and channels, on the sides of tanks and drinking troughs and in thick, tangled masses in low-lying swampy areas. They are not usually toxic but can clog filters, meters, valves and trickle irrigation lines.
  • Blue-green (cyanobacteria) algae can range in colour from yellow to purple. Some types can be highly toxic to humans, livestock and birds. They are capable of very sudden, explosive growth and may appear as a thick, smelly, green, paint-like scum on the surface of a lake or dam, particularly around the shallow edges, down wind, either in clumps or as filaments.

Contributing Factors

There is no single reason why blue-green and other algae have become such a problem in recent years, particularly in summer, but some contributing factors are:

  • algae thrive on nitrogen and phosphorus and these chemicals have entered water systems in large amounts following their use or perhaps over-use in commercial, domestic and agricultural activities (e.g. top dressing, dairy washing, abattoirs)
  • The warmer temperatures and light intensity experienced in the water during summer provide favourable conditions for growth
  • in summer, stratification of water results in higher temperatures in the upper levels of water bodies. Also, nutrients tend to be released from sediments providing nourishment for algae
  • relatively still and stagnant waters favour their growth

These and other more complex factors operate in combination, and no one factor can be pinpointed as a cause of initiation of continuation of a bloom. Blue-green algae blooms can persist for two to three weeks, months and even an entire summer period if conditions are favourable.

What to look for

Outbreaks of blue-green algae often give off a characteristic musty odour. Blooms can vary in appearance from pale to bright fluorescent green, and may appear paint-like or granular in texture. Blue-green algae outbreaks are generally confined to areas of still water with little turbulence.

  

  

Alert Level Framework

A framework of alert levels has been developed and agreed to by water authorities and government agencies throughout Victoria. These have been established to provide a uniform and consistent set of guidelines for water supply authorities which manage waterbodies and have the responsibility of supplying consumers with water that is safe to use and drink.  Alert levels are determined as follows:

Alert level 1 (Low).

These numbers are typical of non-bloom conditions in nutrient enriched waters. The water should be free of visible colour, but some blue-greens may impart tastes and odours to the water.

Alert level 2 (Medium).

These cell numbers tend to indicate that blue-green algae are multiplying. The water may exhibit a green tinge, and musty or organic tastes and odours. Scums may form at cell numbers exceeding 5,000 cells/mL. Alternative drinking water supplies or water treatment must be considered.

Alert level 3 (High).

These numbers represent bloom conditions. The water may be distinctively green and have a strong musty or organically polluted taste and odour. Toxicity must be presumed and the water considered unsafe for human consumption and contact, and unsafe for stock water supply. Scums are often present. Recreation activities involving direct skin contact must be curtailed.

G-MW staff regularly monitor and inspect the region's lakes and irrigation systems for blue-green algae as part of their catchment management work.

A hotline has been set up to provide up-to-date information on blue-green algae alert levels throughout G-MW's region.  All queries, requests for information, or reported sightings should be directed to Goulburn-Murray Water through the algal hotline number 03 5833 5785 (hotline shortcuts). 

Warning signs are erected at sites that have high levels of blue-green algae to assist in alerting the community to the presence of blue-green algae and to warn against certain activities in the affected water. Letters are sent out to potentially affected users and media releases are put in local newspapers to ensure that the wider community is aware of the problem.

Human Health Risks

Direct skin contact with blue-green algae affected water through showering, bathing, swimming, water skiing and other recreational activities may result in a variety of symptoms.  These could include skin irritation and rashes, swollen lips, eye and ear irritation, sore throat, hay fever-like symptoms and asthma.

Ingestion of water contaminated with blue-green algae may cause nausea, vomiting, abdominal pain, diarrhoea, liver complications and muscle weakness.  The severity of symptoms may be proportional to the amount of contaminated water consumed, the particular species of blue-green algae producing the toxins, and to some extent upon an individual's own personal 'in built' immunity to BGA toxins. Medical assistance is recommended if any of these symptoms are experienced.

Risk to Livestock and Other Animals

Livestock including cattle, sheep and poultry may be affected as a result of drinking water contaminated with blue-green algae.  Possible symptoms that stock may exhibit include convulsions, paralysis, liver damage, constipation, abortion and skin sensitivities. Milder cases of algal poisoning in stock can cause loss of appetite, and may cause a consequent decline in milk yield in dairy cattle. In extreme cases, stock deaths can occur following ingestion of high concentrations of potentially toxic blue-green algae. Dogs are particularly susceptible to blue-green algal poisoning because scums can attach to their coats and be swallowed during self-cleaning. If you suspect that your animals are showing any of these symptoms you should seek veterinary advice.

Risk to Irrigated Pasture

Some blue-green algae toxins will remain toxic in a dry form. Continued application of heavily affected waters on pastures (eg from dairy waste recycling dams) can lead to significant toxin build up on foliage. Although this is a rare occurrence requiring special circumstances, this residue could potentially have similar effects to those previously described.

Effect on Plants

Plants do not appear to absorb toxins, however it is recommended that water impacted by blue-green algae does not come in direct contact with parts of plants that may be eaten (ie fruit and vegetables).  Before eating, vegetables and fruit should be thoroughly washed and rinsed with non-toxic water.

Broad-acre agricultural crops are not known to take up toxins. However, blue-green algae are fast growing and can shade and foul rice crops if they occur in bays before the crop establishes a cover above water level, which can cause significant yield loss.

I think there may be blue-green algae in a dam, channel or creek system, what should I do?

A water sample should be collected and sent to an analytical laboratory to positively identify whether blue-green algae are present. Suitable laboratories may include:

Water Ecoscience/ Ecowise Environmental
22 Dalmore Drive

Scoresby Vic 3179
Phone: 03 8756 8000
Fax: 03 9763 1862

La Trobe University
Bendigo
Ph: 03 5444 7890

The Department of Primary Industries is the responsible authority for providing advice about the management of blue-green algae in farm dams and can be contacted on 136 186. In the meantime, we suggest the following:

  • Alternative water supplies be sought.
  • Livestock be kept away from affected water.
  • If no alternative supply is available, pumping water from areas not covered in a scum or deeper areas of the dam  MAY reduce algal exposure and risks.

If in a channel, creek system or major storage contact your local water authority. The contact number for Goulburn-Murray Water is  (03) 5833 5500 or alternatively, phone the Blue-green Algae Hotline on (03) 5833 5785. 

Please note that the use of algicides is prohibited in creeks, rivers and lakes.

Alternative Water Supplies

When algal blooms are present in the water channel or supply point, you should seek alternative water supplies for domestic use and stock watering. Boiling the water will not make it safe and may in fact increase the toxicity of the water. It is difficult to determine the toxicity of the bloom as it can change from day to day. So it is best to assume that all blooms are producing toxins and to act accordingly.

Individuals will have to determine the best options for their particular circumstances.  Options may include good quality bore water, carted water, bottled water or tank water. 

Advice on the safety of alternative sources of drinking water supply may be obtained from local government environmental health officers and urban water authorities.

Advice on the safety and suitability of alternative sources for on-farm use (eg stock watering) may be obtained from the Department of Primary Industries by phoning 136 186 or www.dpi.vic.gov.au and search on blue-green algae.

Treatment

At present, there are few options for the treatment of blue-green algal affected water. Urban water authorities employ sophisticated treatment systems including expensive activated carbon treatment to treat drinking water supplies. Commercially available systems for treating individual household drinking water supplies do exist, although these are not suitable for treating the large volumes of water needed for livestock water supply.

Copper sulphate, or other copper based products, are often promoted as algicides for use in farm dams etc.  These products can have major ecological impacts (eg cause fish fills and kill other 'good' algae), and should never be used in creeks, rivers or lakes.  They need to be applied before algae blooms occur, and don't fix the problem in the long-term (they can actually make the problem worse, as algae release toxins as they die). Specific approval from regulatory authorities (EPA) is required for their use.

Aeration technologies involving mixing of water by the installation of mixing devices has been used in some private and urban water authority storages, but is not generally practicable for the large volumes of water managed by G-MW, or cost effective for small scale (eg. farm dam) applications.

In short, treatment of water for domestic and stock or irrigation use by individuals is likely to be impracticable, however potential sources of information on this option are:

References

  1. Dr Kumar Eliezer, State Water Laboratory, in Aqua Issue 9, Rural Water Corporation, autumn 1994
  2. Dr Anne Graesser, Goulburn-Murray Water, for The Northern Irrigation Cropper, summer 1996/97