Mystery debris that closed two Sydney beaches confirmed to be thousands of ‘tar balls’

Coogee and Gordons Bay beachgoers had been warned not to touch the material. ‘Tar balls’ form from oil spills or seepage at sea

Thousands of black golf ball-sized pieces of debris that washed up on the sand and forced the closure of two Sydney beaches have been confirmed as “tar balls”.

Coogee beach was closed on Tuesday and Gordons Bay beach was closed on Wednesday with beachgoers warned not to touch or go near the “mysterious black, ball-shaped debris”.

Randwick council said on Wednesday evening that “preliminary test results … show the material is a hydrocarbon-based pollutant which is consistent with the makeup of tar balls”.

Hydrocarbons are the chief components of petroleum-based products.

A potential oil slick was spotted off the coast on Wednesday morning, a day after the ball-shaped debris was first found on Coogee beach.

Both Coogee and Gordons Bay beaches remained closed with clean-up efforts under way to safely remove and dispose of the material, the council said.

Council environmental officers had collected samples from Coogee on Tuesday and sent them for testing.

The incident was reported to the Environment Protection Authority and Beachwatch New South Wales.

The council had initially speculated the then unknown material could be “tar balls” formed when oil comes into contact with debris and water – usually as a result of oil spills or seepage.

Council jetskis spotted a suspected oil slick out at sea on Wednesday morning, the Randwick council mayor, Dylan Parker, said. However, it was not yet confirmed.

A dead seagull coated in black floated past the Coogee local Jamie O’Donnell when he was surfing off Gordons Bay on Wednesday morning. “That was the only sign of the oil slick we saw,” he said.

The Port Authority of NSW said no oil spills had been reported by vessels.

“It is the responsibility of all ships to report any spills to the relevant authorities including the Australian Maritime Safety Authority, Transport for NSW and Port Authority,” it said in a statement.

The state environment minister, Penny Sharpe, said earlier on Wednesday that the EPA was working with other government agencies and forensic scientists to identify exactly what the balls were, the source of the contamination and what risks it presented.

Parker said debris balls were also spotted on Wedding Cake Island about 1km off Coogee beach.

“We have engaged an expert occupational hygienist and a specialist waste removal contractor who are currently systematically removing the debris from the beaches in accordance with an agreed safe work method statement developed with the NSW EPA,” the mayor said on Wednesday. “This process will likely continue tomorrow.”

Coogee beach was closed with yellow barricades, orange flags and council signage reading “work in progress” on Wednesday morning. About 20 staff in hi-vis worked along the length of the beach.

The debris balls were picked up one at a time by staff. The balls were placed in mounds above the high-tide mark and covered with sand to avoid them being washed away.

A local barista said Coogee beach was different from a normal morning when “people do laps around the pool or are just out walking”. “Usually you see plenty of people,” he said.

Jennifer, who works at Coogee Express convenience store, said she anticipated business would be quieter so long as the beach was closed. “I think next week [it will] get better,” she said on Wednesday.

Louise Morris, the oil and gas campaign manager at the Australian Marine Conservation Society, said earlier on Wednesday: “If it is oil, we’ve got a clean-up problem on our hands.”

Morris said she suspected “something has happened offshore” and marine life would be harmed.

“Tar balls are normally the result of some oil spill somewhere that has been combined with debris, plastic, whatever it may be,” Morris said.

“Small animals that live on the ocean floor, who are taking in sediment, are going to start ingesting it. We are looking at birds and other animals that get coated in oil [on the water’s surface]. It affects their ability to fly, to feed and to swim.”

Randwick council posted on social media on Tuesday evening: “Coogee beach is closed until further notice after council lifeguards this afternoon discovered mysterious black, ball-shaped debris washed along the length of the beach.”

Beachgoers were advised to avoid the beaches until further notice and not touch the material while the clean-up and investigations continued.

Cover photo: Coogee beach suspected oil slick: beachgoers warned after black balls wash ashore