All Wracks and Sargassum (Fucales)

Sargassum is a genus of large brown seaweed that floats in island-like masses and never attaches to the seafloor. Its leafy appendages and berry-like structures are actually gas-filled pneumatocysts, filled mostly with oxygen, which add the buoyancy that lets the plant float at the surface. Clumps, patches, large rafts and weedlines can stretch for miles across the ocean and give food, refuge and breeding grounds to fishes, sea turtles, marine birds, crabs and shrimp. The sargassum fish, a frogfish, lives its whole life in this habitat, and the rafts are a primary nursery for mahi mahi, jacks and amberjacks. When Sargassum loses its buoyancy it sinks and feeds deep-sea food webs with carbon.