More than 80 per cent of Moreton Bay's seagrass beds were lost in some areas after sediment flowed into the bay in 2011.

Mr Powell said some dugongs could die as a result of the sediment, but said others would leave.

“It's true that if the sea grass is in short supply, a small proportion of the population can be expected to die," he said.

"But most of the dugongs will move away from the area and return as the sea grass beds recover."

Two Griffith University ecologists yesterday told Fairfax Media they believed the sediment – four times as dense as river sediment after January 2011 floods – were now pushing Moreton Bay close to an environmental tipping point.

Mr Powell said flood plumes from the 2010-2011 flood events which caused significant damage to Moreton Bay's seagrass beds, could be higher this time around.

“Sediment washed into Moreton Bay after the Australia Day long weekend storms may be higher than two years ago, given the sediment load in the Brisbane River is four times higher than then,” Mr Powell said yesterday.

“We lost more than 80 per cent of sea grass in some locations and marine life was affected for more than a year afterwards."

Mr Powell said he understood the turtle and dugong populations would recover.

"Indications at the end of last year were that they were recovering fairly well," he said.

However Professor Rod Connolly this week disagreed with Mr Powell.

"What I think is that seagrass beds that were fine last time are now tipped over the edge of what they can cope with," he said.

Lord Mayor Graham Quirk, the chairman of the South East Queensland Council of Mayors, said the sediment flowing into Moreton Bay was on the agenda at the next meeting of the council.

The higher level of sediment came from soil from Lockyer Valley small crop farms, he said.

"The level of sediment there is considerable greater than what you get from the grazing lands around the Stanley (River) through the Wivenhoe Dam," Cr Quirk said.

Healthy Waterways Partnership chief executive Peter Schneider said he supported "a lot" of the issues raised by the two ecologists from the Australian Rivers Institute.

"For the past 12 months or so, we have been saying sediments are our really big issues," he said.

Mr Schneider said the Healthy Waterways Partnership believed a full-day planning workshop – with all levels of government, industry and ecology group at the meeting – could put forward plans.

"If we could get all levels of government there, yes. You can't lose because everything starts with a conversation," he said.