Research shows seaweed could help improve GBR water quality

Seaweed is shaping up as a useful tool in the battle to reduce harmful nutrient run-off on the Great Barrier Reef.

Queensland researchers are growing seaweed in land-based fish farms and using it as a natural filter to draw nutrients out of the water before it reaches the reef.

The method has also worked at a coal-fired power station, as Stephanie Smail reports.

STEPHANIE SMAIL: Nutrient run-off is a well-known enemy of the Great Barrier Reef.

Sediment and chemicals have been blamed for poor water quality in the World Heritage-listed area, and are known to cause outbreaks of the Crown of Thorns starfish.

But a research team from James Cook University has found a way to tackle the problem.

David Roberts says macro-algae - better known as seaweed - is proving very useful. He says seaweed can work as a natural filter in land-based fish and prawn farms, improving the water quality before it reaches the reef.

DAVID ROBERTS: The idea of natural filters is probably familiar to people. You know, we build things like artificial wetlands to deal with stormwater run-off, and this is just a way of harnessing the natural abilities of seaweeds to grow and sequester nutrients from seawater and putting them into intensive systems where they grow really quickly, much more quickly than they would in the wild - they have unlimited nutrient supply, unlimited sunlight, and they grow very, very quickly. So it's really just harnessing the natural abilities of seaweed.

STEPHANIE SMAIL: The natural filter concept has worked in other industries too.

David Roberts says the research team has been using algae to clean up industrial waste water at a coal-fired power station in south-east Queensland. He says it draws contaminants out of the water, bringing the quality up to regulatory standards.

DAVID ROBERTS: The results have been really promising. We've actually shown that we can get most of those elements from concentrations well above regulatory limits to concentrations well below regulatory limits. So it's a really significant improvement in the way wastewater is managed.

The other advantage of doing this work at power stations is we can actually take carbon dioxide from the power station's flue gas emissions and pump that into our cultures, and like any plant or photosynthetic organism, algae actually need that carbon dioxide to grow. So we're recycling carbon as well as treating a waste water problem at the same time.

STEPHANIE SMAIL: The researchers have also had some success in producing crude oil from the seaweed after it's absorbed the waste from the power plant.

David Roberts says the environmental benefits for improving water quality are clear. He also points out there could added benefits for the businesses that use seaweed to filter their wastewater.

DAVID ROBERTS: For a farm to grow in Queensland - a fish farm or a prawn farm to grow - they actually have to demonstrate that they won't increase the amount of nutrient that they discharge to the reef, and that's one factor that's really limited the expansion of fish and prawn aquaculture in Queensland.

And so what our approach does is it gives farms a way of growing without increasing their nutrient emissions. That allows them to increase production of their core business, which is fish or prawns, but it also adds that additional cash crop. The seaweeds we're growing, the edible seaweeds, have a value of anywhere between $10 and $50 a kilogram. So it's actually quite a valuable product as well when you consider that it's solving an environmental issue but also diversifying a business.

MARK COLVIN: David Roberts from James Cook University ending Stephanie Smail's report.

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• Water Treatment & Control
• Water Quality