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Waikato Shallow Lakes Cyanobacterial Warning
Waikato Shallow Lakes Cyanobacterial Warning Update
One lake warning reinstated, another is
lifted
Monitoring results from late June
2010 have shown that the human health threat from
cyanobacteria in Lake Whangape is now acceptably low.
Lake Waahi also remains below the warning level; however levels in Lakes Ngaroto and Waikare are still above the warning level.
Hakanoa has also had its cyanobacteria warning reinstated after the cell count rose more than fourfold since the last measurement in May, lifting the biovolume back up from 1.2 to 8.2mm3/L.
Currently, warnings will be issued when the biovolume exceeds 1.8mm3/L.
This reflects the importance of the size of the cells as a more useful indicator of how much toxin may be in the water.
Environment Waikato is no longer routinely testing Lake Kainui.
Waikato District Health Board medical officer of health Dr Dell Hood reminds the public that test results should be used for general guidance only, as cyanobacteria and their toxins will not be evenly spread through any lake and may be concentrated in some areas by wind and water movements.
“During blooms, lakes should not be used for any activity which involves skin contact with the water,” she said.
“If people choose to do this, they should shower and change their clothing as soon as possible afterwards, even if no symptoms are noticeable.”
Swallowing water from lakes affected by blooms should also be avoided.
While not everyone will be affected, for some, the risks include rash, skin and eye irritation, allergy symptoms such as hayfever and asthma and possibly stomach upsets such as diarrhoea and vomiting.
These effects may not appear until some time after contact with the affected water.
New guidelines for
measuring and responding cyanobacteria in fresh water
recreation sites were published last summer.[1]
Warning
levels now take into account not only the number of known
toxin-producing cells present but also their size.
“In recent years, some warnings may have been overly cautious when the cyanobacterial species present in large numbers was known to have a small cell size,” said Dr Hood
Environment Waikato and Waikato District Health Board’s Population Health service are moving to full use of the new guidelines as information about the cell size of various species found in local lakes is measured.
Warnings are based on the likelihood of cyanobacterial toxin being in the water, not on actual toxin measurements.
As in previous years, testing will take place less frequently over the colder months and the next samples will be collected in late August.
“Up-to-date information on cyanobacterial cell counts is available from local councils and Environment Waikato.
Visit the
Environment Waikato website for up to date results:
http://www.ew.govt.nz/Environmental-information/Rivers-lakes-and-wetlands/healthyrivers/Waikato-River/Algal-Blooms-in-the-Waikato-region/#Heading4
Health advice is available from the Population Health (07) 839 8899 in and out of hours.
ENDS
Waikato District Health Board
Healthy People. Excellent Care
Waikato District Health Board (DHB) employs over 6500 people and plans, funds and provides hospital and health services to more than 391,770 people in a region covering eight per cent of New Zealand.
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