Sargassum Seaweed:

Sargassum, also known as "gulfweed", is a brown algae with an air bladder that allows it to float like a thick blanket on the surface of the water. This seaweed community supports a diverse ecosystem. Floating lines of sargassum provide critical habitat for a wide variety of sea life, including dolphin fish (also called mahi mahi), juvenile sea turtles, and seabirds. Some fish, crabs, shrimp-like creatures and sea slugs float with it and live off it. Pools of fish gather beneath it to catch some of the shade it provides. Sargassum is present in the Gulf of Mexico all year, but is more plentiful in warm weather. Winds and currents typically cause Sargassum to wash up on the beach beginning in May. When it begins to decompose in the sun it can look and smell unpleasant. Sargassum, however, is also an important part of the beach ecosystem. During high tides it is pushed back to the dunes where it dries and decomposes providing a base for other plant life by helping to to build dunes by trapping blowing sand.