Health warning removed for algal bloom in Cust River
March 23, 2017
Health warning removed for algal bloom in Cust River near Skewbridge Road
The Community and Public Health division of the
Canterbury District Health Board has lifted its potentially
toxic cyanobacteria (algal) bloom health warning issued on
the Cust River near Skewbridge Road.
Recent surveys have shown the cover of potentially toxic blue-green algae (benthic cyanobacteria) in the river has decreased and are now below the levels that are of concern to public health.
Dr Alistair Humphrey, Canterbury Medical Officer of Health, says Environment Canterbury’s routine monitoring of rivers and lakes in the Canterbury region has been completed for this summer season.
“It will resume again next summer when there is increased likelihood of cyanobacteria growth,” Dr Humphrey says.
“The public is however reminded that there are still some rivers and lakes where warnings remain in place due to algal blooms.”
• Selwyn/Waikirikiri River at Whitecliffs domain and
• Lake Pegasus
• Lake Forsyth/Te Roto o Wairewa which also has a Rāhui on the lake
• Hurunui River at State Highway 7
• Lake Ellesmere/Te Waihora
These will continue to be monitored and the public advised when the warnings have been lifted.
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.