1 September 2004

Students from the University of Queensland have given the state’s seagrass population a clean bill of health thanks to a new method of testing for contaminants.

PhD students, Kathryn McMahon and Susan Bengtson Nash from UQ’s Centre for Marine Studies and the National Research Centre for Environmental Toxicology (EnTox), discovered that although herbicide residues were still being found in the State’s marine environment they were not having a detrimental affect on the seagrass.

The students have been investigating seagrass health by trialling a new phytotoxicity assay, Tox-Y-PAM, for monitoring phytotoxins in aquatic systems. The environmental assessment took place around southeast Queensland’s Mary River, Great Sandy Straits and Hervey Bay.

Ms McMahon said herbicides were still getting into fresh and marine waters but that there was no measurable damage on seagrass meadows.

“Low concentrations of herbicide were delivered into Hervey Bay and the Great Sandy Straits from the catchment during moderate river flow events. The concentrations detected were close to what is known to impact seagrass photosynthesis but were not high enough to have a significant impact,” Ms McMahon said.

Seagrass not only stabilises the sediment in the marine coastal systems but also provides a major food source for green turtles and dugongs.

The encouraging findings come at a time when Brisbane is celebrating what has become one of the planet’s most precious resources, water. UQ is one of the proud sponsors of the seventh International Riversymposium currently being held in Brisbane (August 31 to September 3).

The symposium has brought together a large group of related experts, including the University’s Senior Deputy Vice-Chancellor Professor Paul Greenfield who was recently included in a list of Australia’s 100 most influential engineers.

This year’s event is focusing on best-practice river management under the theme Threats to sustainable river systems – beating the odds.

Mounting concerns about the environmental impact of herbicides in rivers and water systems have meant a growing requirement for accurate, timely information regarding herbicide residue contamination of aquatic systems.

Ms Bengtson Nash said continued successful development of the assay could provide a simple, accurate and inexpensive tool for monitoring phytotoxins in the aquatic environment.

“Conventional methods of detection remain limited in terms of practicality due to their focus on the detection of a select number of previously characterised chemicals,” Ms Bengtson Nash said.

“They do not provide information regarding the biological significance of contaminants or combinations of contaminants.

“Further, these methods are expensive and require facilities and equipment that may not be widely accessible to, for example, smaller councils or isolated farming communities.”

Ms McMahon, supervised by lecturer in Marine Biology Dr James Udy, and Ms Bengtson Nash, supervised by Associate Professor Jochen Mueller from EnTox collected water and sediment samples over a period of three years. The samples were analysed for herbicides at the EnTox laboratories.

The study is due to be published in the Marine Pollution Bulletin international journal early next year.

Ms McMahon said the Environmental Protection Agency in Maryborough were using the report to help with management and planning in the affected areas.

Media: For more information or photos, contact Kathryn McMahon (telephone 07 3365 9154 or mobile 0403 820 104) or Susan Bengtson Nash (07 3274 9147 or mobile 0405 350 208) or Chris Saxby at UQ Communications (telephone 07 3365 2479, email: c.saxby@uq.edu.au).