December 4, 2008
Warm weather and low flows in South Canterbury may produce toxic algal growths in rivers or ponds
The prolonged warm dry weather in South Canterbury is prompting warnings about rivers developing potentially toxic algal
growths. Environment Canterbury warns that as the warm weather continues and river flows reduce, some rivers or ponds
may develop toxic algal blooms. This can be particularly dangerous to dogs or stock and in some cases can cause human
health problems.
Dogs have become sick and in some cases died from eating or licking algal mats in previous dry summer periods both in
Canterbury and parts of the North Island.
The toxin-forming, naturally-occurring black algae, Phormidium, is found in rivers throughout the country, but only
forms problematic thick blooms in some sites under the right flow conditions.
People are warned to look out for areas of rivers where black mats of algae are growing or forming scums, and keep dogs
out of these waters and avoid swimming in heavily invested areas. Dogs and stock should also be kept away from stagnant
ponds, especially those which have bright green or red scums or have strong odours.
Environment Canterbury staff do regular visual checks at popular swimming sites for the presence of potentially toxic
algal blooms.
ENDS