The Mekong River—the longest river in Southeast Asia—flows from southern China through Tibet, Laos, Cambodia, and Vietnam, where it enters the South China Sea. The sediments it carries on the 2,700-mile (4,350-km) journey form the vast, extremely fertile Mekong Delta, which occupies southeast Cambodia and southern Vietnam. One of the greatest rice-growing areas in Asia, the densely populated delta region has been called a “biological treasure trove.” What did scientists recently discover there? Discuss