31 October 2023
Whether you’re a local or
visiting for the summer, take a moment to check the water
for algal blooms in lakes and rivers. During the warmer
months lakes and rivers can be affected by blooms of
blue-green algae which are potentially toxic. To reduce your
chance of becoming unwell, it is important to know when it
is not safe to have contact with the water.
“Algal
blooms can develop rapidly and unpredictably and can
sometimes produce toxins that are harmful for people as well
as animals. It is best to avoid contact with the water if it
looks discoloured, has an unusual smell, has green or brown
particles suspended in it, or if you can see scum or
leathery mats of algae on the surface or on the bottom of
the waterway,” says Dr Gregory Evans, Te Whatu Ora Medical
Officer of Health for Toi Te Ora Public
Health.
“These blooms have the capacity to release
toxins into the water which can cause significant ill-health
to anyone who has contact with the water. The toxins can
affect the nervous system causing numbness and difficulty
with breathing, and also sparking asthma attacks. Contact
with the water can also cause skin rashes, stomach upsets
and visual problems,” says Dr Evans.
Lakes are
typically dominated by free-floating algal blooms, while
rivers are more prone to algal blooms that grow in mats
attached to rocks at the bottom. They can also build up at
the shoreline.
“Algal mats and scum may also
accumulate along the shoreline of lakes or rivers so it’s
especially important that parents ensure that children avoid
contact with these as they may be toxic,” says Dr Evans.
You should seek medical advice from your GP if you become
unwell after having contact with the recreational
water.
Dogs are also particularly at risk of serious
illness if they consume or have contact with toxic algae.
They should be kept away from the water if it looks like
there may be a bloom. They may also eat algal mats that
accumulate in and around rivers.
A health warning is
issued by Toi Te Ora Public Health if recreational water
monitoring results provided by Regional Councils show a site
to have high levels of blue-green algae.
Find
information on local health warnings on the following
channels:
