Sargassum, or Gulfweed, is a free-floating brown algae which often washes ashore on Southern beaches. Some of that which washes up comes from the Sargasso Sea, a part of the Atlantic Ocean between Bermuda and the West Indies. The Sargassum which originates in the Sargasso Sea seems to reproduce vegetatively at sea, and is independent of coastal Sargassum populations. Other types of Sargassum grow attached to the ocean bottom in shallow coastal waters in the South.
Sargassum, either that which has actually floated in from the Sargasso Sea, or the “locally-grown” variety, has a yellowish-brown leafy stalk which pea-size air bladders or vesicles on it. These spherical air bladders look like golden berries. They keep the Sargassum afloat.
Sargassum weed clumps are like floating cruise ships with all sorts of passengers. As many as 70 species live on the weed clumps when they are at sea. Some of the “passengers”include several species of fish (for example the Sargassum Fish), seahorses, pipefish, and triggerfish; a swimming crab and a shore crab; shrimp; goose barnacles; anemones; a type of sea spider; a type of sea slug; and several species of polychaetes, hydroids, bryozoans, and amphipods.
Some of these creatures will remain on the seaweed “ship” as it comes close to shore or washes in. You can pick up a clump of Sargassum, hold a bucket under it, shake the seaweed, and see what you find.
At certain times of the year, storms and/or strong winds and waves may blow large quantities of Sargassum onto the beach — so much that the sand is nearly covered with clumps of the Gulfweed.