Mr Garrett said on Sunday maritime authorities were working hard to minimise the accident's impact on the reef.
"The government is very conscious of the importance of the Great Barrier Reef environment and ensuring that impacts on its ecology are effectively managed," he said in a statement.
"Authorities have been working through the night to determine what risks the stranding of the Shen Neng 1 poses to the Great Barrier Reef."
Mr Garrett said the Great Barrier Reef Marine Park Authority, Maritime Safety Queensland and the Australian Maritime Safety Authority had jointly authorised the use of a dispersant to minimise potential environmental damage.
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It will be trialled to see whether it works, and once its performance has been assessed, a decision will be made on whether to keep using the dispersant or not.
He confirmed the nation's oil spill response plan had swung into action as soon as authorities were told of the accident, and that an incident control centre had been established.
Mr Garrett said aircraft surveying the site since first light had discovered patches of oil in the water around the ship.
