As rivers wash sediment toward the sea, they carve elaborate deltas like that of the Rio Cauto in Cuba. Over time these sediments build up marshes, swamps, lagoons, and other wetlands that provide critical habitat and flood control. Sediment also washes into the bay, where it interacts with the coral reefs (light green lines on the lower left) and the species that live there. (Image credit: L. Dauphin/USGS; via NASA Earth Observatory)
