LONDON/BENGALURU—Trading on the London Metal Exchange (LME) resumed on Tuesday morning after a power outage as the world’s top marketplace for industrial metals struggles with declining volumes. Activity resumed at 0615 GMT following the outage at a third-party data centre on Monday evening, the LME said. The exchange, owned by Hong Kong Exchanges and Clearing Ltd., migrated all systems to its backup data centre and trading was proceeding as normal, a spokesperson said. The LME has faced declining volumes, competition from other exchanges, and the COVID-19 pandemic, which forced the open outcry trading floor to close for 18 months. Trading on the floor of the exchange resumed in September last year, but the exchange decided to shift closing prices to its electronic system, Select. The exchange been looking to find ways to boost lagging volumes. Overall lots traded for the first 11 months of 2021 slipped by 7 percent, latest …