Gracilaria is a genus of red algae (Rhodophyta) notable for its economic importance as an agarophyte, as well as its use as a food for humans and various species of shellfish. Various species within the genus are cultivated in Indonesia.

Gelidium is a genus of thalloid red algae comprising 124 species. Its members are known by a number of common names. Specimens can reach around 2–40 cm (0.79–16 in) in size. Branching is irregular, or occurs in rows on either side of the main stem. Gelidium produces tetraspores. Many of the algae in this genus are used to make agar. Chaetangium is a synonym.

Gelidium species have been collected, pressed and maintained in herbaria and personal collections from the 1850s onwards since seaweed collecting became a popular pastime for the middle classes as well as scientists in Europe and North America. These numerous well-documented specimens can provide information beyond taxonomy.

SuhriaVittataThis name is currently regarded as a synonym of Gelidiumvittatum (Linnaeus) Kützing

Ulvalactuca, also known by the common name sea lettuce, is an edible green alga in the family Ulvaceae. It is the type species of the genus Ulva. A synonym is U. fenestrata, referring to its “windowed” or “holed” appearance.

Ulvalactuca is a thin flat green algae growing from a discoid holdfast. The margin is somewhat ruffled and often torn. It may reach 18 centimetres (7.1 in) or more in length, though generally much less, and up to 30 centimetres (12 in) across. The membrane is two cells thick, soft and translucent, and grows attached, without a stipe, to rocks or other algae by a small disc-shaped holdfast.

Green to dark green in colour, this species in the Chlorophyta is formed of two layers of cells irregularly arranged, as seen in cross-section. The chloroplast is cup-shaped in some references but as a parietal plate in others with one to three pyrenoids. There are other species of Ulva which are similar and not always easy to differentiate.

Sargassum is a genus of brown (class Phaeophyceae) macroalgae (seaweed) in the order Fucales. Numerous species are distributed throughout the temperate and tropical oceans of the world, where they generally inhabit shallow water and coral reefs, and the genus is widely known for its planktonic (free-floating) species. Most species within the class Phaeophyceae are predominantly cold-water organisms that benefit from nutrients upwelling, but the genus Sargassum appears to be an exception. Any number of the normally benthic species may take on a planktonic, often pelagic existence after being removed from reefs during rough weather; however, two species (S. natans and S. fluitans) have become holopelagic—reproducing vegetatively and never attaching to the seafloor during their lifecycles. The Atlantic Ocean’s Sargasso Sea was named after the algae, as it hosts a large amount of Sargassum.

Caulerpa is a genus of seaweeds in the family Caulerpaceae (among the green algae). They are unusual because they consist of only one cell with many nuclei, making them among the biggest single cells in the world. A species in the Mediterranean can have a stolon more than 3 metres (9.8 ft) long, with up to 200 fronds. This species can be invasive from time to time.

Some species of Caulerpa are edible. The two most commonly eaten are Caulerpalentillifera and Caulerparacemosa, both called “sea grapes” in English. Both are traditionally harvested in the wild and sold in local markets in Southeast Asia, Oceania, and East Asia. They are eaten raw in salads and have a characteristic “sea” flavor and a crunchy texture.

Only C. lentillifera is cultivated in aquaculture. Its cultivation began in the 1950s in Cebu, Philippines, after accidental introduction of C. lentillifera to fish ponds.[7] This was followed by Japan in 1986, where it was cultivated in tanks in the tropical waters of Okinawa.[8] Commercial cultivation has since spread to other countries, including Vietnam, Taiwan, and China (in Fujian and Hainan). Most are for domestic consumption, but they are also exported to Japan.

Eucheuma, commonly known as gusô, is a seaweed algae that may be brown, red, or green in color. Eucheuma species are used in the production of carrageenan, an ingredient for cosmetics, food processing, and industrial manufacturing, as well as a food source for people in the Philippines and parts of Indonesia and Malaysia. Eucheumacottonii – cultivated in the Philippines – is the particular species known as gusô. Other species include Eucheumadenticulatum, and several species of the genus Kappaphycus, including K. alvarezii. Since the mid-1970s, Kappaphycus and Eucheuma have been a major source for the expansion of the carrageenan industry.