Hundreds of BHP staff have downed tools for one of the most significant industrial disputes to hit Australia's resources sector in a quarter of a century.Unions said about 200 workers at the mining giant's operations in Port Hedland walked off the job at 2pm, disrupting ongoing work at Australia's largest bulk export port.They were warmly welcomed by supporters and union staff, who had assembled before the protected industrial action got underway.Unions have inflated this protest balloon, known as "Scabby the Cat", outside the port. (ABC Pilbara: Andrew Seabourne)A "family-friendly" picket has been established outside the gates, with sausages cooking on the barbecue, and pickleball and face painting for assembled children.The eight-hour stoppage is expected to cost the company millions of dollars in lost revenue, with foregone royalties also set to hit the state government's budget bottom line.The combined ports unions — the Electrical Trades Union (ETU), Australian Manufacturing Workers Union and the Western Mine Workers Alliance — have been locked in negotiations with BHP for months.Union representatives began gathering outside the port late on Tuesday ahead of the strike action. (ABC Pilbara: Andrew Seabourne)The miner took the matter to the Fair Work Commission last week seeking the regulator's assistance for an outcome.A BHP spokesperson labelled the strike action as disappointing, and said it had contingency plans in place to limit disruption."We remain committed to bargaining in good faith and believe involving the Commission is the most constructive, transparent and fair way to achieve the best outcome," the spokesperson said.Supporters play pickleball outside the BHP operations during the strike. (ABC Pilbara: Andrew Seabourne)Mining lobby says economy at riskThe strike comes as the miner reported record quarterly production, with Western Australia's Chamber of Minerals and Energy arguing the action put that success and investment at risk.Chamber chief executive Aaron Morey said the strike was "uncharted territory", criticising the federal and West Australian Labor governments for failing to intervene.BHP has a large presence in the Town of Port Hedland in WA's Pilbara. (ABC Pilbera: Andrew Seabourne)"The world is watching this afternoon … international customers and international investors are watching," he said."We've got some unions up in the north of the state that are holding up Australia's biggest economic asset."And they're holding it up for face painting and bouncy castles."About 40 ETU members gathered in Brisbane. (Supplied: ETU)But ETU state secretary Adam Woodage pointed to recent investment decisions by BHP, and record production figures announced today."The reason they've had record production is because they've got a highly-skilled workforce that delivers those results here in Port Hedland," Mr Woodage said.BHP has a big presence in the Town of Port Hedland as it uses its port to export iron ore. (ABC Pilbera: Andrew Seabourne)"The ETU remains ready, willing and able to negotiate; they can ring me this afternoon, and I'll go in the gates here if they want to cut a deal."ETU members in Brisbane and Melbourne rallied in support of the strike action today.Email address