A controversial $444.3 million federal grant to the Great Barrier Reef Foundation is necessary to protect the reef against the threats of climate change, its chairman says.

John Schubert gave evidence for the first time to a Senate committee in Canberra on Tuesday.

The inquiry wants to know why the government granted the six-year funding stream to the small not-for-profit foundation without going to tender, and how it plans to use the money.

Dr Schubert said he was unaware the foundation would receive the near half-a-billion dollars before a meeting with former prime minister Malcolm Turnbull and then-energy minister Josh Frydenberg in April.

He said he has not spoken to Mr Turnbull since the meeting in Sydney, which lasted less than an hour.

“You asked was I surprised … but my overwhelming initial reaction was: ‘This is fabulous news for the Great Barrier Reef. This is what is needed’,” Dr Schubert said when asked about his reaction to receiving the grant.

Dr John Schubert gave evidence to a Senate inquiry on Tuesday. Photo: AAP

He said the reef faced ongoing threats against climate change and it needed to be protected as it has already been “altered forever”.

“I think every coral reef in the world is in danger,” Dr Schubert said.

Dr Schubert “quickly” came to the conclusion that the foundation had the capacity to leverage the funding to raise more money from the private sector to protect the reef.

There was no requirement made from Mr Turnbull about how much it had to leverage.

Other directors, including respected marine scientist John Gunn, said they believe the foundation was chosen for the grant because of its “track record”.

Dr Schubert said the foundation “recognised very openly that climate change is the greatest threat to our Great Barrier Reef”.

Despite this, he said it was not the foundation’s place to take political positions on other projects that could contribute to climate change, including the proposed Adani Carmichael coal mine in Queensland.

Critics of the grant have raised concerns about potential conflicts of interest and commercial interests, given the foundation has a number of corporate backers from the resources sector.

Labor and the Greens have questioned why the foundation received the grant, arguing the public money could be better spent elsewhere.

Labor has announced its intentions to reclaim the funds, if it wins government.

Foundation managing director Anna Marsden said there had been no negative impact on operations or support since the announcement, despite the criticism.

The foundation has told the inquiry it has projects due to start next year.

The inquiry will hear further submissions and evidence about the controversial grant on Friday.

-AAP