Hot weather increases chance of blue-green algae in coastal creeks

Tweed Shire Council

Residents and visitors are urged to avoid swimming and surfing in coastal waters, creeks and estuaries if any evidence of blue-green algae is detected.

The naturally occurring blue-green algae Trichodesmium has been seen in the lower reaches of Cudgen Creek, particularly in the area near the river mouth in recent days, although marine winds have dispersed some of the bloom.

Council’s Senior Program Leader – Environmental Health Marcela Lopez said although it could happen at any time, blue-green algae was more likely to bloom in local waterways from August to April.

“As the temperature rises, we often see Trichodesmium along the Far North Coast at this time of year,” Ms Lopez said.

“It is often mistaken for oil or slimy effluent slicks on beaches and in rivers where it has been blown onshore by winds and tide.

“While Trichodesmium is a blue-green algae, it can come in a lot of other interesting colours including orange, grey, brown, green and purple. It decays quickly, usually turning greenish and then pink-red as it dies. It smells bad, like rotting plant matter or chlorine gas, with some people describing it as a ‘fishy’ smell.”

Ms Lopez said blooms of some Trichodesmium could produce toxins that may pose a health risk.

“While the direct risk to human health is very low, we encourage people to avoid wading, swimming or surfing in water where a bloom is visible and keep animals away,” she said.

“We are also advising residents not to eat shellfish from affected waters and the water should not be used for potable water supply. If you come into contact with the algae, rinse it off with soap and fresh water as soon as possible.”

Trichodesmium is a member of the phyto-­plankton family and plays an important role in the aquatic food chain.

Calm conditions, northerly currents and warm water temperatures can increase growth, with blooms disappearing naturally.

Being safe is the foundation of a healthy Tweed community. Head to to find out more including a handy fact sheet on the issue.

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