Freshwater bleaching of corals could occur this year as a result of flood waters from Queensland’s overflowing rivers pouring into the Great Barrier Reef, the marine park authority has warned.

The Great Barrier Reef Marine Park Authority told Senate estimates hearings in Canberra on Monday that there is a chance corals hit by mass bleaching in 2016 or 2017 could be damaged again by one of several impacts from the flooding disaster.

Bruce Elliot, the authority’s acting chief executive, said scientists were out monitoring flood plumes on the reef and it was possible that freshwater bleaching could affect inshore reefs.

The discharge of flood waters into the reef could also smother seagrass meadows, which poses a threat to animals such as dugongs and turtles that rely on seagrass as a primary food source.

It has led to deaths of animals after past disasters, such as cyclone Yasi in 2011.

“This event has not been without its ramifications for the Great Barrier Reef,” Elliot said.

“There has been major to moderate flooding of the rivers from the Daintree to the Mackay regions.”

He said it could be weeks or months before authorities had a full picture of the natural disaster’s effect on the marine park.

David Wachenfeld, the authority’s chief scientist, told the hearing there were “extensive” flood plumes on the reef and that unusual wind conditions were carrying them further east and offshore than would normally be expected.

Scientists from James Cook University and the Australian Institute of Marine Science were monitoring the spatial extent of the plumes and their chemical content, he said.

Wachenfeld said scientists had already detected some areas on the reef where the water salinity had dropped to almost half its usual level because of the flooding.

This causes stress for corals and other marine life used to a saline environment, and freshwater bleaching of corals can result.

Wachenfeld said a substantial part of the central Great Barrier Reef was affected by flood waters.

“I’m certainly not able to put any kind of a figure on the spatial extent of the park that’s affected by the flood plumes but I think I can safely say that they are extensive because there are rivers flooding all the way from the Whitsundays in the central Great Barrier Reef, right up to Cape Tribulation in the northern Great Barrier Reef,” Wachenfeld said.

Elliot told the hearing that the recent cooler weather in the region had “markedly” reduced the chance of a mass thermal bleaching this year compared with earlier predictions.

He said forecasts in coming months would be critical in determining the outcome for the reef this season.

In hearings earlier in the day, environment department officials were quizzed on the activities of the environment minister, Melissa Price, who has been questioned for her lack of public appearances during the flooding and other natural disasters this summer, including the record-breaking January heat and the Tasmanian bushfires.

Labor and Greens senators asked officials what public comment the minister had made on the disasters, as well as what meetings she had had with groups including the Wilderness Society, which has said Price failed to respond to correspondence requesting a meeting.

Officials confirmed the Bureau of Meteorology had briefed the minister on the floods but took a question on notice as to whether she had made any public comment on the mass fish kill in Menindee Lakes.

“Surely you can answer that,” Greens senator Sarah Hanson-Young said to the department.

Liberal senator Simon Birmingham said “a minister’s output and their contribution is not measured by their interviews”.