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High-tech science identifies biggest reef polluters

New research led by scientists from the University of Queensland and The Nature Conservancy has identified which rivers are most responsible for polluting the Great Barrier Reef. The research also sheds light on the vast distances that pollution travels once discharged from the river mouth.  These findings offer a way to prioritise critical land-based actions to protect the Reef.

“Our results indicate that the Burdekin, Fitzroy, Tully and Daintree Rivers posed the greatest nutrient risk (in terms of dissolved inorganic nitrogen) to coral reefs during the three seasons examined”, said Dr Nick Wolff, lead author of the research, from The Nature Conservancy. “We were surprised to discover the extent of pollution from the Burdekin River during 2011 when 275 reefs up to 450 kilometres north of the river mouth were impacted.

 

Map showing the asymmetric extent of pollution from the Burdekin River, northern Queensland during 2011. Reefs coloured green are those that had high nitrogen exposure and were dominated by Burdekin pollution. The Burdekin dominated the nitrogen signal on 275 reefs and up to 450 km to the north of the Burdekin River mouth. Without this study, maps like this wouldn’t be possible.

We could use this approach to target where the biggest pollution problems are and act on these sooner and more effectively by focusing limited resources on those catchments where action will have the greatest potential benefit for the reef.”

“Understanding the flow and direction of pollutants from each river and their catchments and tracking where these pollutants end up has been a missing piece in the puzzle to protect the reef” said Dr Wolff. “Our research used sophisticated oceanographic models and ‘virtual dyes’ to trace the movement of pollutants in rivers flowing onto the reef to help resolve this puzzle”.

When dissolved inorganic nitrogen enters the ocean from river runoff it stimulates the growth of algae. On the reef, algae can smother corals. In the water, planktonic algae can block sunlight reaching the corals. Increased plankton also promotes the breeding success of the destructive Crown-of-Thorns Starfish. Reducing nutrients flowing via rivers to the reef is critical to help sustain the health of the Great Barrier Reef (GBR).

The study also included scientists from the Australian Institute of Marine Science, James Cook University and the UK Centre for Environment, Fisheries and Aquaculture Science. They used a GBR-wide hydrodynamic model to learn how nitrogen moved through 16 individual river plumes during three wet seasons up to 2013. They then used direct observations to calibrate tracer values, allowing them to estimate the contribution of each river to the GBR’s overall exposure during each season.

Read the research paper

Dr Wolff is available for interview.

All media enquiries to: Tony Jupp, Associate Director of Communications, TNC Australia, tjupp@tnc.org