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Mud suffocating Moreton Bay ecosystems

The amount of mud in Brisbane's Moreton Bay has more than doubled in the past 45 years and it’s casting a shadow on the underwater habitat.

New research from the University of Queensland reveals the disappearance of seagrass in many areas due to suffocation by mud, which now covers more than 50% of Moreton Bay’s floor.

“Seagrasses are a light-needing plant and they're a basis for a lot of marine life [including coral, turtles and dugongs] in the bay,” said researcher James Lockington, from UQ’s School of Civil Engineering.

“Fine mud particles entering Moreton Bay result in less sunlight striking the sea floor. It can also smother plant and animal communities.”

The recent survey of 223 sites from the Gold Coast to Pumicestone Passage found that mud covered 800 square kilometres of the bay, compared to just 400 square kilometres observed during the last major survey in 1970.

The university is now looking into what effect flooding has had on mud coverage over the years.

“One of the projects we're working on at the moment is to start taking cores so that we can get a volume of the mud … because there's only very rough estimates of how much each flood event moves in,” Lockington said.

Changes in land usage were also likely to be largely responsible for the increase in mud cover.

“People on the cusp of our lifetime now remember the Brisbane River being clear,” Lockington said.

“We've come in and changed land use to urban or high-intensity agriculture so we've affected the sediment flow.

“Now we've got a brown Brisbane River plus a lot of the smaller tributaries – like Logan and Caboolture River – are also getting filled with more and more sediment runoff from the catchment areas.”

Lockington said he hoped the research would support Moreton Bay ecosystem health assessments and guide regional management actions.