A three-stage warning system is being used to minimise the health risks of blue-green algae to people who use Lake Horowhenua. The system recognises the different health risks posed by different activities on the Lake.
The current Lake Horowhenua Domain Board health risk level is:
The health risk levels are:
|
Health risk level |
Blue-green algae |
Lake use restrictions2 |
|
GREEN |
Up to 20,000 cells per millilitre. |
No restrictions apply. |
|
AMBER |
Between 20,000 cells per ml and 100,000 cells per millilitre. |
Avoid algae scums. No swimming or drinking. Boating not restricted. |
|
RED |
More than 100,000 cells per millilitre and toxicity confirmed. |
Lake closed to all use. |
1.Sampling, cell estimates and toxin testing carried out by Horizons Regional Council
2.Lake restrictions made by Lake Horowhenua Domain Board.
Blue-green algae are very small plant-like organisms that can build up to huge numbers under favourable conditions in lakes and oceans. They are common and have been found in lakes like Lake Horowhenua for many years. They cause health concerns in other lakes in New Zealand such as Lake Rotoiti near Rotorua.
Some blue-green algae carry toxic substances and have been linked to negative effects on human and animal health. The toxic substances can cause skin rashes, nausea, tummy upsets, and tingling and numbness around the mouth or tips of fingers. If toxin levels are really high, drinking the water could result in severe liver damage.
It seems sensible that the Lake Horowhenua Domain Board manage recreational use of the lake, rather than have anyone affected by the blue-green algae.