14 May 2019
For immediate release
Health warning removed for algal bloom in the Otukaikino/Waimakariri confluence near SH1 and Main North Road bridges
Canterbury District Health Board’s Community and Public Health unit has lifted the algal bloom health warning that was issued on the 7 March 2019 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 Ramon Pink says Environment Canterbury’s surveying of the rivers and lakes in the Canterbury region for algal blooms has ended for this season and will resume next summer when there is increased likelihood of cyanobacteria growth. Only two rivers, the Ashley at SH1 and the Ashley at the Rangiora-Loburn Bridge remain in warning and will continued to be monitored until warnings can be removed. The public will be notified of this in due course.
Facts about cyanobateria:
• 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.
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