Health Warning Lifted For Harmful Algal Bloom In South Bank Tributary Of The Waiau Uwha River At Waiau Bridge

Health New Zealand lifted its harmful algal bloom health
warning issued for the South Bank Tributary of the Waiau
Uwha River at Waiau Bridge.

Recent cyanobacteria
surveys of the South Bank Tributary of the Waiau Uwha River
at Waiau Bridgehas shown the cover of potentially toxic
harmful algae (benthic cyanobacteria) have reduced and are
now below levels that are of concern to public
health.

Dr Claire Salter, Medical Officer of Health
for the National Public Health Service, says Environment
Canterbury’s monitoring of South Bank Tributary of the
Waiau Uwha River at Waiau Bridge has finished for this
season and will resume in November when there is increased
likelihood of cyanobacteria
growth. 

Facts about
cyanobacteria:

• Cyanobacteria appears as
  dark brown or black mats attached to rocks along the
  riverbed.
• A low cover of the algae can occur
  naturally but can increase rapidly during warmer months.
  Algal blooms are influenced by a combination of available
  nutrients in the water and sediments (such as nitrogen and
  phosphorus), a sustained period of low and stable flows, and
  favourable weather conditions (for example increased
  temperature, calm days).
• It often has a strong musty
  smell and algal toxin concentrations can vary over short
  periods.
• Although high river levels will remove the
  algal bloom, detached mats can accumulate along the shore
  and increase the risk of exposure to toxins.
• If a
  health warning is in place avoid contact with the
  water.
• Although district or city councils may place
  warning signs, these may not be seen at the numerous river
  access points, hence the need for people/ dog-walkers to
  treat every low-flowing river cautiously.
• Pets that
  show signs of illness after coming into contact with algal
  mats should be taken to a vet
  immediately.

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