Serious health warning over 'sewage-like' water quality in Queensland bay

Experts have issued a serious health warning over swimming in Queensland's Moreton Bay, north-east of Brisbane after the water quality was likened to sewage.

Mud and sediment washed down the Brisbane River from floods has equated to 180 years' worth of sewage being released into Moreton Bay, a University of Queensland study has found.

The dangerous sediment is covering up to 98 per cent of the bay and has spread to Moreton, North Stradbroke and Bribie Islands.

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Materials and microplastics in the mud could be potentially fatal to local marine life and kill coral and seagrass - the major food source for fish, the experts have warned.

The mud could also cause algal blooms, which is dangerous to humans.

"When it is blooming there is certainly advice not to go into those waters because it can be an irritant to the skin," Dr Alistair Grinham said.

People are warned against swimming in the bay as it poses a health risk.