Canterbury District Health Board’s Community and Public Health unit has lifted its algal bloom health warning issued for
the Otukaikino/Waimakariri confluence near SH1 and Main North Road bridges
Recent cyanobacteria surveying of the water in the Otukaikino/Waimakariri confluence has shown the quantity of
potentially toxic blue-green algae (benthic cyanobacteria) in the river has decreased and the cover is now below the
levels that are of concern to public health.
Medical Officer of Health, Dr Alistair Humphrey says Environment Canterbury’s surveying of the Otukaikino/Waimakariri
confluence will continue to the end of this summer and then will resume next summer when there is increased likelihood
of cyanobacteria growth.
Facts about cyanobacteria:
• Appears as dark brown/black mats attached to rocks along the riverbed.
• The algae occur naturally but can increase rapidly during warmer months.
• It often has a strong musty smell and algal toxin concentrations can vary over short periods with changing
environmental conditions.
• 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.
For further information visit:
For more information on Mahinga kai: