Lake warnings for toxic algae

Read our latest lake warnings for toxic algal blooms.

Lake warnings for toxic algal blooms

Warnings in place

30 April 2010

The concentration of potentially toxic blue-green algae present in Lake Ellesmere/Te Waihora has decreased and the risk to health is now considered minimal. The health status has been downgraded by Community and Public Health, as shown below. A health warning remains in place for Lake Forsyth/Te Roto O Wairewa, which has a bloom of the toxic blue-green algae Nodularia. The details of this health warning are also shown below. A warning remains in place for Lake Rotorua (Kaikoura) where a bloom of the potentially toxic algae Microcystis and Anabaena is present. Health warning regarding cyanobacteria (blue-green algae) bloom in Te Waihora/Lake Ellesmere removed Medical Officer of Health Dr Ramon Pink has removed a health warning regarding Te Waihora/Lake Ellesmere because concentrations of cyanobacteria (blue-green algae) have decreased. The risk of health problems as a result of contact with the water is now considered minimal, although drinking water from the lake is not recommended. In February 2010, Dr Pink said that due to increased amounts of cyanobacteria found in Te Waihora/Lake Ellesmere, it was unsafe for drinking or recreational use. Contact with water containing high levels of blue-green algal blooms can lead to symptoms such as allergic reactions, asthma, eye irritations, rashes and blistering around the mouth and nose, and/or abdominal pain, cramps and diarrhoea. Further information regarding the current health status of Canterbury rivers and lakes can be obtained by contacting Community and Public Health on 03 364-1777 or Environment Canterbury. The Environment Canterbury website is updated regularly with the latest information regarding recreational water quality. Health Warning re blue-green algal bloom: Te Wairewa/ Lake Forsyth Dr Alistair Humphrey, Medical Officer of Health advises that due to increased levels of algal bloom and associated toxins, until further notice, Te Wairewa/Lake Forsyth water is unsafe for ingestion or recreational use and may cause health problems. Regular monitoring of recreational water is carried out and consistently high levels of algal bloom indicate that this lake will remain unsuitable for recreational use or drinking until further notice. The intention of this media release is to warn the public that ingestion of the water can be fatal to animals, including dogs, sheep, cattle, fish and birds. Lake water is unsafe to drink, and the Medical Officer of Health recommends that drinking water from suitable sources is consumed by persons using the Little River Rail Trail and nearby recreational areas. In addition, with regard to humans, swimmers have been known to develop adverse reactions after bathing and showering in water containing blue-green algal blooms. These include allergic reactions, asthma, eye irritations, rashes and blistering around the mouth and nose, gastrointestinal disorders, (abdominal pain, cramps, diarrhoea). Recreational users including duck shooters, fishermen and boat users are to exercise caution with regards to recreational contact with lake water. Toxin levels will increase in shell fish rendering them potentially harmful to health, therefore consumption of shell fish from the lake should be avoided until further notice. Warning signs advising people of these risks will be placed around the lake. For further information, or in the case of illness or suspected illness after ingesting water containing the algal bloom, you should seek medical advice from your doctor or in the case of animals, your veterinarian.

The concentration of potentially toxic blue-green algae present in Lake Ellesmere/Te Waihora has decreased and the risk to health is now considered minimal. The health status has been downgraded by Community and Public Health, as shown below.

A health warning remains in place for Lake Forsyth/Te Roto O Wairewa, which has a bloom of the toxic blue-green algae Nodularia. The details of this health warning are also shown below.

A warning remains in place for Lake Rotorua (Kaikoura) where a bloom of the potentially toxic algae Microcystis and Anabaena is present.

Health warning regarding cyanobacteria (blue-green algae) bloom in Te Waihora/Lake Ellesmere removed

Medical Officer of Health Dr Ramon Pink has removed a health warning regarding Te Waihora/Lake Ellesmere because concentrations of cyanobacteria (blue-green algae) have decreased.

The risk of health problems as a result of contact with the water is now considered minimal, although drinking water from the lake is not recommended.

In February 2010, Dr Pink said that due to increased amounts of cyanobacteria found in Te Waihora/Lake Ellesmere, it was unsafe for drinking or recreational use.

Contact with water containing high levels of blue-green algal blooms can lead to symptoms such as allergic reactions, asthma, eye irritations, rashes and blistering around the mouth and nose, and/or abdominal pain, cramps and diarrhoea.

Further information regarding the current health status of Canterbury rivers and lakes can be obtained by contacting Community and Public Health on 03 364-1777 or Environment Canterbury.

The Environment Canterbury website is updated regularly with the latest information regarding recreational water quality.

Health Warning re blue-green algal bloom: Te Wairewa/ Lake Forsyth

Dr Alistair Humphrey, Medical Officer of Health advises that due to increased levels of algal bloom and associated toxins, until further notice, Te Wairewa/Lake Forsyth water is unsafe for ingestion or recreational use and may cause health problems. Regular monitoring of recreational water is carried out and consistently high levels of algal bloom indicate that this lake will remain unsuitable for recreational use or drinking until further notice.

The intention of this media release is to warn the public that ingestion of the water can be fatal to animals, including dogs, sheep, cattle, fish and birds. Lake water is unsafe to drink, and the Medical Officer of Health recommends that drinking water from suitable sources is consumed by persons using the Little River Rail Trail and nearby recreational areas.

In addition, with regard to humans, swimmers have been known to develop adverse reactions after bathing and showering in water containing blue-green algal blooms. These include allergic reactions, asthma, eye irritations, rashes and blistering around the mouth and nose, gastrointestinal disorders, (abdominal pain, cramps, diarrhoea). Recreational users including duck shooters, fishermen and boat users are to exercise caution with regards to recreational contact with lake water.

Toxin levels will increase in shell fish rendering them potentially harmful to health, therefore consumption of shell fish from the lake should be avoided until further notice.

Warning signs advising people of these risks will be placed around the lake.

For further information, or in the case of illness or suspected illness after ingesting water containing the algal bloom, you should seek medical advice from your doctor or in the case of animals, your veterinarian.

General advice on lake algal blooms

If there is a health warning in place:

Never swim or take part in any activity that may result in accidental consumption or exposure to water affected by algal blooms if a health warning is in place for that area, even if there are no visible signs of a bloom. Do not let stock or dogs swim or drink from the water.

If a health warning is in place, it means that cyanobacteria (blue-green algae) are present in large numbers in that bay/lake. Cyanobacteria are capable of producing toxins that are harmful to humans and animals if swallowed or if exposed to skin (such as may occur when swimming, skiing or kayaking etc).

If there is no health warning in place:

Wind blowing onto shore may concentrate a bloom in a bay and make it unsafe for recreational contact. This can occur at any time of the year, but is more common in warm summer months. Hence, even if no warnings are in place for a lake or bay, you should still assess the situation carefully before entering the water.

Caution: If the water is cloudy, discoloured, or has small globules suspended in it, it is better to be cautious and totally avoid that lake or bay.

Even if the water appears completely normal to the naked eye, it can still have large numbers of algae present. If you experience health symptoms (such as those described below) that come on within minutes of contact with the water, you should avoid further contact with the water and, if symptoms persist, contact Community and Public Health 03 379 9480 or see your doctor.

Cyanotoxin health symptoms

Swimmers have been known to develop adverse reactions after bathing and showering in water containing blue-green algal blooms. These include allergic reactions, asthma, eye irritations, rashes and blistering around the mouth and nose, gastrointestinal disorders (abdominal pain, cramps, diarrhoea). Some of these can be caused by the mere presence of large numbers of algal cells in the water, but some symptoms are related to the release of toxins by the bloom. These toxins are colourless and odourless. They are unaffected by boiling the water and can persist in the water after the bloom has subsided. They can also be released at any stage of a bloom and may or may not be localised in a bay.