Sydney’s famous Bondi Beach and other beaches around the Australian city were closed on Thursday as authorities investigated mysterious tar balls that had washed ashore.
The dark, sticky, golf-ball-sized clumps were first reported on Tuesday at Coo gee Beach, prompting a series of beach closures along the city’s coastline. They also include Bronte, Tamarama, Gordons Bay and Clovelly and the northern end of Maroubra Beach, all of which are closed until further notice while the debris is cleared and removed.
People have been advised not to swim near or touch the debris. The city council in Randwick, a Sydney suburb that is home to four of the beaches, said preliminary test results showed the clumps were tar balls, formed when oil comes into contact with debris and water.
“We don’t yet know what has happened to cause the debris to wash up on our beaches,” Mayor Dylan Parker said in a statement on Thursday. “However, we continue to work with the relevant authorities to ensure the safety of the public and to clean up our beaches.”
The Environment Protection Authority of New South Wales, the state in which Sydney is located, said similar debris had also been found on Coggon, Frenchmen’s, Little Bay and Malabar beaches. It said it was investigating the origin of the debris and whether it posed a risk to the community and the environment.
“At this stage, the origin and contents of the balls are still a mystery. However, the EPA is conducting extensive testing on a number of samples,” the statement said, adding that the presence of hydrocarbons, the main constituents of petroleum-based products, could not be confirmed, as reported by Randwick City Council.
The tar balls are “quite a chemical mystery,” William Alexander Donald, a chemistry professor at the University of New South Wales Sydney, told NBC News on Thursday.
Preliminary analysis by a team of UNSW researchers confirms that the tar balls are from weathered oil, either from a crude oil spill or natural oil seepage from the ocean floor.
“They are formed from oil that has been spilled into the ocean, and probably crude oil, based on our chemical analysis,” Donald said.
The tar balls are not just unsightly. They can harm marine ecosystems, affecting animals such as seabirds, turtles and fish by disrupting their movement and feeding. The toxins in them can also leak into the water, Donald said, potentially threatening marine biodiversity.
The appearance of the tar balls on beaches “not only damages Australia’s pristine coastal reputation, but also threatens the health of ecosystems that support industries like fishing and tourism,” he said in a news release.
Tar balls of this type are “relatively uncommon” in Australia, Donald said. But they have appeared elsewhere, including on beaches in California and along Gulf of Mexico coastlines after the Deepwater Horizon oil spill in 2010.
“There are still a lot of questions about what’s in these gooey lumps,” Donald said. “It’s quite an analytical challenge.”