It’s the height of summer in Sydney, a time when tourists and locals are usually flocking to the city’s famous beaches. But nine beaches were shut to the public this week – including well-known Manly – after more ball-shaped debris washed ashore. Similar sticky round globules have been found on many of the city’s beaches over the past six months, forcing some of them to close temporarily. The New South Wales environment minister, Penny Sharpe, has said the balls remain a “genuine mystery”. Coogee beach suspected oil slick: beachgoers warned after black balls wash ashore – video But there’s a