Tens of thousands of environmentalists have petitioned the Great Barrier Reef Marine Park Authority to reject a massive dredging project at Abbot Point.

A petition signed by 70,000 people has been handed to the Great Barrier Reef Marine Park Authority (GBRMPA) in a final bid to stop a major Queensland coal port expansion.

The Abbot Point project near Bowen involves dumping three million cubic metres of dredged spoil within the marine park area to expand the port.

Federal Environment Minister Greg Hunt approved the project in December, subject to what he says are strict environmental conditions.

But GRMPA has the final say over whether the dredging will go ahead. A decision is due by next Friday.

A petition calling on the proposal to be scrapped was delivered to the authority in Townsville on Friday.

Paul Oosting, from campaign group GetUp, says those who signed the petition are concerned the dredged spoil could damage marine life and jeopardise the state’s reef-based tourism industry.

“The flow-on effects are really worrying both in terms of the health of the Great Barrier Reef, its World Heritage status and importantly people’s livelihoods,” he told AAP.

Whitsundays dive operator Tony Fontes is concerned some of the reef’s beauty may be lost if the expansion goes ahead.

North Queensland Bulk Ports, the corporation that has proposed the dredging project, has said it could possibly make the water cloudy during a short period and may damage seagrass.

However, a spokesman has said it would unlikely affect other flora and fauna.

Queensland Resources Council chief executive Michael Roche has urged GRMPA to make its decision based on scientific evidence, rather than online campaigns by “anti-coal and anti-gas activists”.

If the expansion goes ahead, an extra 70 million tonnes of coal each year – worth $1.4 billion to $2.8 billion – would go through the port.