Seaweed

This past summer, beaches in Florida and the Caribbean have been piled high with foul-smelling sargassum seaweed, often in record amounts. It is the visible sign of a vast marine ecosystem that emerged in 2011 and now spreads across a 5,500-mile-long belt from Mexico to West Africa and Florida to Brazil.

Susan Hand Shetterly has written about wildlife and wetlands for more than thirty years, in both articles and books, including "Settled in the Wild," a…