Last updated 04 June 2014
Recent water testing has shown that concentrations of blue-green algae (cyanobacteria) are now below the trigger levels that are of concern to public health. Environment Canterbury will continue to monitor the lagoon on a fortnightly basis until two consecutive negative samples (that are below alert levels), are achieved by which time the algal bloom would have completely cleared. The public will be informed if testing shows that concentrations have increased and there is risk to public health again.
Last updated 02 May 2014
Recent water testing has shown that concentrations of blue-green algae (cyanobacteria) are now below the trigger levels that are of concern to public health. Environment Canterbury will continue sampling the lake on a monthly basis.
Long term water testing indicates that there is a regular bloom of the potentially toxic cyanobacteria Anabaena and/or Microcystis present. There is a permanent health warning advising people to avoid contact with water at this lake. Environment Canterbury continues to monitor the lake on a regular basis.
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).
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.
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.
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