Cyanobacteria found in Taranaki rivers

Taranaki residents are being urged to be cautious around rivers, with potentially toxic cyanobacteria detected earlier in the season than usual.

Taranaki Regional Council has found exposed mats of cyanobacteria in four rivers—the Manganui, Waingongoro, Kaupokonui and Waiwhakaiho Rivers—raising health concerns for both swimmers and pets.

Cyanobacteria, also known as blue-green algae, is a naturally occurring algae that often grows in rivers on rocks as thick brown or black mats. It has the potential to release toxins that can pose significant health risks to both humans and animals. When these mats become exposed on the edges of rivers, they can have a distinctive, unpleasant smell, often described as musty or swampy.

Council Water Quality Scientist Angela Collins says if you see these mats, it’s safest to stay out of the water and keep a close eye on children and pets.

“Children are at greater risk because their smaller body size means they need to ingest less toxin to become seriously ill, while dogs may be attracted to the musty smell.

“This is earlier than we typically expect to find cyanobacteria in our rivers and is likely due to the drier winter we had - heavy rainfall and high water flow help to flush cyanobacteria.”

The Council is closely monitoring cyanobacteria levels at selected rivers and lakes (where it is called planktonic) as part of its Can I Swim Here? programme, which began this week and runs through until March.

“As we kick off the Can I Swim Here? programme, we want to remind the public of the risks posed by cyanobacteria and encourage everyone to be mindful when planning a swim—especially in the rivers where we’ve found the mats.”

Alongside cyanobacteria, water is tested for E. coli at freshwater sites and enterococci at coastal sites, both of which are indicators of possible faecal contamination.

Ms Collins says any time water doesn’t look or smell right, it’s safest to stay out.

If you come into contact with water contaminated with cyanobacteria, wash it off with clean water as soon as possible. If ingested, contaminated water may cause nausea, vomiting, diarrhoea, abdominal pain and, in more serious cases, liver or kidney damage. If you experience any of these symptoms, contact your doctor immediately.

For more information on the Can I Swim Here? monitoring programme, including long-term swimmability grades, weekly test results and current health warnings, go to www.lawa.org.nz/explore-data/swimming.