Following the recent incident of a dog becoming ill after ingesting algae in Walter Park in northern Christchurch, dog owners are being reminded to be vigilant around water where dark brown/black algal mats are present.

Hill-fed rivers with low flows and warm temperatures are generally the highest risk locations at this time of year, however mats of the toxic cyanobacterium (blue-green algae) Phormidium can also establish in small ponds and slow-flowing waterways in both urban and rural areas.

When walking dogs near such waterways, dog owners are advised to check the water's edge and if dark brown/black mats or scums are present then ensure that your dog does not come into contact with them.

Specific warnings to river users, including swimmers and dog owners, remain in place for the Waipara, Ashley, upper Selwyn, Opihi, Pareora and upper Otaio rivers because Phormidium is still present at these places.

For further information or in the case of illness or suspected illness, seek advice from your doctor. If animals become sick, contact your veterinarian immediately.

For further information contact Dr Cathy Kilroy, NIWA (on behalf of Environment Canterbury) on 03 343 7883 or speak to your environmental health officer at your local district or city council.

Further information on health risks is also available from Community & Public Health on 03 364 1777.

Or see: http://ecan.govt.nz/services/online-services/monitoring/swimming-water-quality/Pages/river-warnings.aspx