Spanish authorities are expanding a ban on harmful fertilizers around a saltwater lagoon on the country’s Mediterranean coast, where several tons of dead fish have washed up in recent weeks. Once a magnet for tourism and a sanctuary for marine life, the Mar Menor in Murcia, on Spain’s Southeastern Mediterranean coast, has seen fish stocks plummet in recent years, with similar mass die-offs occurring in 2016 and 2019. Residents began seeing dead fish and crustaceans on Aug. 16. “We calculate that some 20 tonnes have died to date,” said Jose Luis Garcia, director of the World Wildlife Fund’s marine programs in Spain, two weeks ago. The beaches were closed for two weeks while a clean-up operation got underway to remove the fish carcasses. Murcia is one of Spain’s main producers of fruit and vegetables, with much of the produce exported to northern Europe. The Murcia government estimates that every day …