Friday 16 December
Check for lake closures before you leave home
Environment Bay of Plenty’s Kim Ackers sampling a Bay of Plenty lake
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Visitors to the Rotorua lakes can check out the best places to swim – before they even leave home.
At different times of the year, some of the lakes are unsafe for recreation because of algal blooms. When that happens,
the Medical Officer of Health will issue an official health warning for a specific bay or even a whole lake.
However, the news doesn’t always get around. And it can be a real nuisance for visitors who discover their lake of
choice is closed when they get there, says Environment Bay of Plenty environmental scientist Matt Bloxham. “They’ve
packed up the kids and the car, or even the boat, and then find they have to go somewhere else.”
Because of this, Environment Bay of Plenty has worked out different ways people can access the latest health warning
information. If they are on-line, they can check www.envbop.govt.nz, Environment Bay of Plenty’s website. Otherwise,
they can phone 0800 ENV BOP (368 267) at any time of the day or night. After hours, they simply follow the directions to
the latest health warnings.
Health warnings are also publicised over the radio and with signs at the edge of affected lakes.
However, Mr Bloxham warns, algal blooms can form over a matter of hours, so people still need to take care and use
common sense. If the water looks milky green, has a surface layer, or has globules floating in it, “play it safe and go
elsewhere”, he says.
Environment Bay of Plenty recently stepped up its schedule for checking blue-green algae levels in four lakes that
hosted potentially harmful blooms last summer. Since November, Lake Rotorua, Lake Rotoiti, Lake Rotoehu and Lake Okaro
have undergone weekly rather than monthly sampling at nearly 20 locations. Other lakes will be monitored if they show
signs of deterioration.
Mr Bloxham says the more intense monitoring will continue until blooms subside, probably next winter.
Samples are taken from both the lake edge and the middle of some lakes. Mid-lake sampling helps scientists gauge the
gradual build-up of algae to give early warning of blooms.
Blue-green algae are microscopic plants that occur naturally in most waterbodies. However, algae can multiply rapidly
when the water has too many nutrients, like nitrogen and phosphorus. Under calm conditions, they can then form in
surface blooms, which are sometimes toxic.
ENDS