A cruise ship spilt 28,000 litres of waste and greywater into the Great Barrier Reef Marine Park in August, a Senate estimates hearing has heard.
The general manager of reef protection for the Great Barrier Reef Marine Park Authority, Simon Banks, confirmed the 28 cubic metre spill, which occurred off the coast of Innisfail, to Greens senator Larissa Waters on Monday.
The Australian Maritime Safety Authority had alerted the marine park authority of the P&O spill, he said, noting that Maritime Safety Queensland would have responded to the incident.
An investigation into the spill is ongoing.
Earlier, Great Barrier Reef Marine Park Authority chairman Russell Reichelt told Labor senator Anthony Chisholm that climate change posed the greatest threat to the health of the reef.
A possible El Nino weather system could spark further coral bleaching on the reef this summer, he added.
Half of the reef's shallow cover coral was lost in the summers of 2016 and 2017 from coral bleaching and severe weather.
Dr Reichelt says the warnings in a recent major climate report - that coral reefs would be destroyed if global temperatures increased by two degrees Celsius - should be heeded.
"I think it is a credible analysis, that report has pulled together information that has been with us for some time," he told the hearing.
"It's critical for the planet to meet those (Paris) targets."
The Great Barrier Reef Marine Park Authority is yet to brief Environment Minister Melissa Price on the threats to the reef as outlined in the United Nations climate report.
