Harmful algal blooms

What is an algal bloom?

Algae and cyanobacteria are simple organisms that live in the water. Algae and cyanobacteria can rapidly grow out of control, or “bloom,” when water is warm, slow-moving, and full of nutrients (for example, due to runoff containing fertilisers and sewage).

Blooms can occur in fresh water, marine water, and brackish water. Blooms can look like foam, scum, mats, or paint on the surface of the water. A bloom can change the colour of the water to green, blue, brown, red, or another colour. Some algal blooms may not be visible.

Harmful algae

Algae and cyanobacteria can sometimes cause harm to people, animals, and the environment. An accumulation of algae which may be harmful to humans and animals is known as a harmful algal bloom. Harmful algae can be found in both marine (salt water) and freshwater environments.

Some types of algae can cause irritation and allergic reactions on direct contact, while others may also produce harmful toxins (poisons). Toxins produced by harmful algal blooms in a marine or freshwater environment can impact human and animal health. Seafood harvested from algae-affected water can also put our health at risk.

Harmful algal blooms will remain as long as there are favourable conditions – including warmth, sunlight and low flow rates.

Blooms can last from weeks to months – it is difficult to predict when they will clear.

Cooler, windy weather or increased water flow may reduce or stop algal blooms.

It is important to note, not all algae and cyanobacteria produce toxins, and not all blooms are harmful.

Harmful algae exposure symptoms

Contact with harmful algae can cause various illnesses and symptoms depending on the type of algae and your exposure.

Direct skin contact

Direct skin contact with harmful algae can cause skin and eye irritation.

Inhalation

Inhalation of fine spray or droplets from algae-affected water can cause mild respiratory effects and symptoms similar to hay fever. This most commonly occurs during recreational water-contact activities like swimming, water-skiing, jet-skiing and boating.

Drinking or consuming harmful algae

Drinking algae-affected water or consuming food (such as fish or shellfish) containing toxins can lead to gastroenteritis, which can induce vomiting, diarrhoea, fevers and headaches.

These toxins may also affect the liver or nervous system.

If you are concerned for your health, see your GP immediately.

Pets and livestock can also be affected by harmful algae. If you think that your animals are unwell, see your vet.

How to avoid exposure to harmful algae in water

To reduce your exposure to algae-affected water:

• Look out for water that is discoloured or where visible scums are present. These scums are a build-up of algae that settles along the edge of the water – where you are more likely to make contact.
• Do not swim and avoid water sports where you may make direct contact with algae-affected water.
• Do not allow children to touch, swallow or swim in algae-affected water (and always supervise them when swimming). Children tend to have more sensitive skin than adults. They are also more likely to accidentally swallow or inhale harmful water which makes them more at risk to algae-related poisoning.
• Try to make sure children in your care are aware of the dangers of harmful algae.
• Follow advice on any information warning signage about harmful algal blooms.
• Avoid contact with the water until authorities advise there is no longer a risk.
• If you suspect that your local waterway is affected by harmful algae, contact the local waterway manager for further advice.

Remember, in some circumstances, water that is affected by harmful algal blooms may not be visible and may not smell any different. If in doubt, contact your local authority or find out more about the latest waterway warnings via Emergency Victoria.

What to do if you are exposed to algae-affected water

If you come into contact with algae-affected water:

• Immediately leave the water.
• Remove any traces of algae by thoroughly washing and rinsing your skin and hair, contaminated clothes and wetsuits in clean water.
• Wash and dry all clothing (including wetsuits) and equipment in clean water. Wetsuits used for water sports may increase the risk of rashes. Any algal material can get trapped inside the wetsuit and be in contact with the skin for long periods.

If you feel ill after contact, seek medical advice.

How to tell if a bloom is present

There are some ways to tell if waterways are affected by harmful algal blooms. These include:

• Look for warning signage and follow the advice given.
• Check the Department of Environment Land Water and Planning (DELWP) blue-green algae and Emergency Victoria websites.
• If there is no signage, look for discolouration and scums on the surface of the water.
• Consider whether the area is prone to harmful algal blooms.
• If in doubt, take a precautionary approach and follow the advice outlined in this fact sheet.

Keeping animals safe from harmful algae

Pets and livestock can be poisoned from contact with or ingestion of harmful algae. Precautions may include:

• Do not let animals swim in algae-affected areas.
• Avoid walks along banks where scums accumulate.
• Do not let animals drink algae-affected water.
• If you are a livestock owner, continuously check water supplies frequently for harmful algae, and keep livestock away from algal blooms.

Animal exposure to harmful algae – first aid

If an animal comes into contact with affected water or scums:

• Wash them thoroughly with fresh water before drying so they do not swallow algae while grooming their fur.
• If you are concerned about an animal’s health, consult a vet as soon as possible.

Seafood contaminated with algal toxins

Fish, shellfish and crustaceans can ingest the toxins produced by harmful algae. These toxins can concentrate in shellfish and the internal organs of fish and some crustaceans.

Toxin levels can remain elevated in aquatic life for several weeks to months after an algal bloom has dissipated.

Eating seafood containing toxins can lead to serious illness.

Cooking or freezing the seafood does not destroy the toxins that cause illness.

When there is a harmful algal bloom:

• Avoid direct contact with algae-affected water.
• Do not consume recreationally caught shellfish and crustaceans.
• Gut and gill fish prior to cooking or freezing.

Seafood in areas without warning signs

Seafood can be affected even in places where there are no warning signs. This is because it not always easy to tell if a harmful algal bloom is present or whether there has been one previously.

Certain rivers and lakes in Victoria are particularly prone to harmful algal blooms. Some seafood can move in and out of algae-affected waters and may be caught in an area where a bloom is not apparent.

If you are unsure whether there is a harmful algal bloom, take a precautionary approach and follow the above advice.

Precautions for consuming fish contaminated with algal toxins

You can still catch and release, or harvest fish from algae-affected waters, as long as you take certain precautions:

• Wash the fish in clean water.
• Gill and gut (fillet) the fish prior to freezing or cooking.
• Put internal organs in the rubbish – it is likely that the fish has swallowed algal toxins, so don’t feed the leftovers to animals.
• Do not eat whole fish harvested from algae-affected waters.

When algal blooms die and start to break down, they use up oxygen in the water, which creates an environment that can suffocate fish.

If you see fish that are dead, dying or swimming erratically, do not touch or eat them.

You can report this to the EPA on Tel.1300 372 842.

Precautions for consuming crustaceans contaminated with algal toxins

Crustaceans (such as crabs, prawns, yabbies and crayfish) may also concentrate toxins in their internal organs.

Exercise caution when consuming recreationally caught crustaceans, especially when water quality is poor.

Do not consume recreationally caught crustaceans where there is a harmful algal bloom.

Avoid shellfish poisoning

Do not eat any shellfish (such as pipis, mussels, oysters, clams, cockles and wedge shells) from algae-affected water. Shellfish are more likely to accumulate dangerous levels of algal toxins and other harmful substances from the water.

You can become ill with shellfish poisoning if you collect and eat shellfish affected by toxins from a harmful algal bloom. Shellfish poisoning can cause serious illness and potentially death.

Symptoms of shellfish poisoning can occur from minutes to hours after eating affected shellfish. These may include:

• Tingling or numbness
• Weakness
• Blurred vision
• Difficulty breathing
• Vomiting
• Diarrhoea

Cooking or freezing the shellfish does not destroy the toxins that cause shellfish poisoning.

There is always a risk of illness from eating wild shellfish harvested where water quality is poor.

Harmful algae and water supply

If your local water business supplies your drinking water, they will manage any algae risks. If you have any concerns about the quality of your drinking water supply, contact your local water business.

Private water supply

If you use a private drinking water supply, you can prevent algae growing by:

• Sealing your water tank.
• Ensuring the pipes or fittings do not receive sunlight.
• Keeping up to date with information on private drinking water supplies on the Victorian Department of Health website.

Untreated water

Do not use untreated algae-affected water for drinking, showering or washing.

Boiling algae-affected water does not remove toxins.

Information related to irrigation and livestock can be found on the Agriculture Victoria website.

Watering your garden with algae-affected water

Avoid using algae-affected water on your lawn and garden beds. It may affect the growth of plants, and poses a risk to anything that might contact the wet surface. Spray irrigation can also produce very fine, airborne water droplets which can lead to toxins being inhaled.

If there is no other water source, minimise water spray on your garden by using drip irrigation, soaker hoses or a watering can and avoid directly watering the edible portion of any plants.

Harmful algae and motor neurone disease (MND)

There is no consistent evidence that exposure to harmful algae causes motor neurone disease (MND) in humans. Likewise, there is no evidence that people living in the vicinity of algae-affected water are at increased risk of developing the disease.

Where to get help

• Your GP (doctor)
• Your local vet
• Water Unit, Department of Health, Victoria Tel.1300 761 874 (during business hours)
• Blue-green algae updates, Department of Environment, Land, Water and Planning, (DELWP), Victorian Government
• Vic Emergency for the latest incidents and warnings in Victoria
• Environment Protection Authority (EPA), Victoria, Tel.1300 372 842 (24 hours, 7 days)
• Your local council
• Your local water corporation
• Agriculture Victoria
• Health Translations - Blue green algae (cyanobacteria), Victorian Government