Fireweed thrives on rise of mud (12/1/2007)

Fireweed washes onto the beach at Bribie Island - a major issue for the local community. Photo: Ron Johnstone

Removing sediment and reducing industrial runoff into Moreton Bay will not only help control fireweed but improve the general health of the Bay, UQ research shows.

Scientists from UQ's Coastal Resource Management (CRM) Unit have shown that fireweed, a toxic blue-green algae, spreads by feeding on a cocktail of nitrogen, iron and phosphorous compounds found in sediment in the Bay.

They've found that as water temperature increases, natural processes unleash tonnes of nutrients and compounds including metals, which feed the fireweed bloom.

Fireweed or Lyngbya majuscula contains toxins that turn some marine animals off their food and can also cause rashes, itches, burns, tingles blistering and breathing problems.

CRM Coordinator Associate Professor Ron Johnstone said clearing fine sediments out of waters entering the Bay was critical to minimising blooms.

"There's no silver bullet or quick fix for this," Associate Professor Johnstone said.

"We need to manage the release of dissolved substances into our coastal waters but also increase the focus on reducing the fine sediment that also passes into the Bay from its surrounding catchments.

"The fine sediment is from mud that comes from different land uses including all the bank erosion that occurs and all of the bits of organic matter that come off agriculture and out of sewerage and stormwater drains."

Dr Johnstone presented his findings to representatives of the Caboolture Shire Council and the Bribie Island Environment Protection Association at Bribie Island on Monday night.

He said the 2007 fireweed bloom covered about 10 square kilometres in Deception Bay.

Blooms in previous years had reached 40 square kilometres, but the summer bloom took longer to die off than previous years.

He said his team including colleague Associate Professor Tony Chiffings, had devised new scientific models and conducted the first comprehensive study of the fireweed's lifespan.

It was previously thought that nitrogen alone promoted fireweed blooms.

But he said it was groundbreaking that his team had shown it was a mix of heavy metals, particularly iron and phosphorous, that nourished fireweed.

The research has been conducted as part of the South East Queensland Healthy Waterways research strategy.

Master of Science student Machiko Kurokawa is one of several postgraduate students working on the project.

Note: This story has been adapted from a news release issued by The University of Queensland

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