Noosa's troubled waters as river health shows rapid decline
Noosa River's key biodiversity indicators, its sand and mud-dwelling species, have taken a third to two-thirds hit over a 20 year period.
A rapid decline in prawns and other small animals fish and crabs feed on is sounding alarm bells for river health experts involved in the Bring Back the Fish research program.
Data from 2018 was compared against previous assessments completed in the same locations in 1998 with a 30-65 per cent decline recorded.
It was most likely triggered by sediment build-ups in the system.
Professor Greg Skilleter from the University of Queensland led the research team and said the study took an unexpected turn when there weren't enough prawns for their analysis.
"We were surprised to find very low numbers of prawns and other small animals in comparison to 20 years ago, particularly in spring when numbers should normally be high," Professor Skilleter said.
"The overall conclusion was that the abundance and diversity of the benthic animals in the Noosa River is now severely depleted compared with historical levels," he said.
Dr Simon Walker, a marine ecologist who has studied the Noosa River for the past six years, said Professor Skilleter's work provided a highly valuable baseline and framework for the future.
The study was the third component of the Bring Back the Fish research program, a joint initiative of the Noosa Biosphere Reserve Foundation, Noosa Parks Association and The Thomas Foundation, aimed at understanding how to improve biodiversity in the Noosa River.
Foundation chair Rex Halverson said that although water quality in the Noosa River was rated an A-, the reports didn't measure biodiversity nor provide a complete picture of ecological health.
"The Noosa River is the lifeblood of the Noosa community," he said.
"It supports us economically and has significant cultural and environmental value, so it's important we preserve it.
"The Bring Back the Fish program addresses the core components to building resilience in the Noosa River ecosystem - sediment, structure and fish food source - the latter the focus of this study," he said.
Noosa Parks Association president Michael Gloster said his group wanted a Noosa River that ran blue, not brown.
"Professor Skilleter's rigorous scientific study of a Noosa River in decline steels our resolve," Mr Gloster said.
"Professor Skilleter's research points to the most likely impact on these animals is due to fine sediment building up in the system."
The Thomas Foundation director Rowland Hill said the report confirmed the biodiversity decline in the Noosa River system and made Noosa Council's recent endorsement of The Nature Conservancy's management plan for the oyster reef project even more timely.
"The Thomas Foundation has worked for the past six years to establish this Noosa Council/TNC partnership, confident of the benefits TNC's involvement will bring to resolving the river system's environmental challenges," Mr Hill said.
BRING BACK THE FISH KEY POINTS:
• Sampling of the benthic communities were undertaken over two periods in May (Autumn) and November (Spring) 2018 - the most extensive sampling ever conducted in the Noosa River system.
• A build-up of fine sediment in the system is the most likely cause of the decline in these animals.
• Data from 2018 was compared against previous assessments completed in the same locations in 1998 with a 30-65% decline in number of benthic species recorded in 2018.
• Ongoing monitoring relative to this new baseline provides a valuable early warning mechanism to measure the health of the estuary into the future