Seaweed: Multicellular marine macroalgae including some members of red (RHODOPHYTA), green (CHLOROPHYTA), and brown (PHAEOPHYTA) algae. They are widely distributed in the ocean, occurring from the tide level to considerable depths, free-floating (planktonic) or anchored to the substratum (benthic). They lack a specialized vascular system but take up fluids, nutrients, and gases directly from the water. They contain CHLOROPHYLL and are photosynthetic, but some also contain other light-absorbing pigments. Many are of economic importance as FOOD, fertilizer, AGAR, potash, or source of IODINE.Phaeophyta: A division of predominantly marine EUKARYOTA, commonly known as brown algae, having CHROMATOPHORES containing carotenoid PIGMENTS, BIOLOGICAL. ALGINATES and phlorotannins occur widely in all major orders. They are considered the most highly evolved algae because of their well-developed multicellular organization and structural complexity.Sargassum: One of the largest genera of BROWN ALGAE, comprised of more than 150 species found in tropical, subtropical, and temperate zones of both hemispheres. Some species are attached (benthic) but most float in the open sea (pelagic). Sargassum provides a critical habitat for hundreds of species of FISHES; TURTLES; and INVERTEBRATES.Fucus: A genus of BROWN ALGAE in the family Fucaceae. It is found in temperate, marine intertidal areas along rocky coasts and is a source of ALGINATES. Some species of Fucus are referred to as KELP.Laminaria: A genus of BROWN ALGAE in the family Laminariaceae. Dried pencil-like pieces may be inserted in the cervix where they swell as they absorb moisture, serving as osmotic dilators.Ulva: A genus of GREEN ALGAE in the family Ulvaceae. Commonly know as sea lettuces, they grow attached to rocks and KELP in marine and estuarine waters.Chondrus: A genus of RED ALGAE, in the family Gigartinaceae. The species Chondrus crispus is a source of CARRAGEENAN.Gracilaria: A genus of RED ALGAE in the family Gracilariaceae. It is a highly commercial SEAWEED and a source of AGAR.Tidal Waves: Water waves caused by the gravitational interactions between the EARTH; MOON; and SUN.Rhodophyta: Plants of the division Rhodophyta, commonly known as red algae, in which the red pigment (PHYCOERYTHRIN) predominates. However, if this pigment is destroyed, the algae can appear purple, brown, green, or yellow. Two important substances found in the cell walls of red algae are AGAR and CARRAGEENAN. Some rhodophyta are notable SEAWEED (macroalgae).Caulerpa: A genus of toxic marine GREEN ALGAE found throughout tropical and subtropical seas. One species, Caulerpa taxifolia, is highly invasive and produces the poison caulerpenyne, deadly to marine organisms though not humans.Laurencia: A genus of RED ALGAE in the family Rhodomelaceae. Some species are a rich source of chlorine-and bromine-containing metabolites which show significant antibacterial activity.Undaria: A genus of BROWN ALGAE, in the family Alariaceae, native to Japan, Korea, and China. The edible SEAWEED Undaria pinnatifida is also called wakame.Bahamas: A chain of islands, cays, and reefs in the West Indies, lying southeast of Florida and north of Cuba. It is an independent state, called also the Commonwealth of the Bahamas or the Bahama Islands. The name likely represents the local name Guanahani, itself of uncertain origin. (From Webster's New Geographical Dictionary, 1988, p106 & Room, Brewer's Dictionary of Names, 1992, p45)