It is hard to describe the putrid stench of the decaying sargassum seaweed blanketing miles of shoreline in Soubise, a fishing village in Grenada. The pungent odour wafts into passing vehicles, persisting long after they have left the Caribbean island’s coves, where the ocean has deposited masses of the seaweed, which turns red then black as it rots. Many residents of Soubise, one of the areas worst affected, say they have learned to live with the problem, which has plagued the island, and others like it, for years. Last week scientists in Florida said they thought they had identified a