Algae is an informal term for a large and diverse group of photosynthetic, eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular microalgae, such as Chlorella, Prototheca and the diatoms, to multicellular forms, such as the giant kelp, a large brown alga which may grow up to 50 metres (160 ft) in length. Most are aquatic and lack many of the distinct cell and tissue types, such as stomata, xylem and phloem that are found in land plants. The largest and most complex marine algae are called seaweeds, while the most complex freshwater forms are the Charophyta, a division of green algae which includes, for example, Spirogyra and stoneworts.
Coralline algae are red algae in the order Corallinales. They are characterized by a thallus that is hard because of calcareous deposits contained within the cell walls. The colors of these algae are most typically pink, or some other shade of red, but some species can be purple, yellow, blue, white, or gray-green. Coralline algae play an important role in the ecology of coral reefs. Sea urchins, parrot fish, and limpets and chitons feed on coralline algae. In the temperate Mediterranean Sea, coralline algae are the main builders of a typical algal reef, the Coralligène ("coralligenous"). Many are typically encrusting and rock-like, found in marine waters all over the world. Only one species lives in freshwater. Unattached specimens may form relatively smooth compact balls to warty or fruticose thalli.
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 in the genus are cultivated among Asia, South America, Africa and Oceania.
Monostroma is a genus of marine green algae (seaweed) in the family Monostromataceae. As the name suggests, algae of this genus are monostromatic. Monostroma kuroshiense, an algae of this genus, is commercially cultivated in East Asia and South America for the edible product "hitoegusa-nori" or "hirohano-hitoegusa nori", popular sushi wraps. Monostroma oligosaccharides with degree of polymerization 6 prepared by agarase digestion from Monostroma nitidum polysaccharides have been shown to be an effective prophylactic agent during in vitro and in vivo tests against Japanese encephalitis viral infection. The sulfated oligosaccharides from Monostroma seem to be promising candidates for further development as antiviral agents. The genus Monostroma is the most widely cultivated genus among green seaweeds.
Limu, otherwise known as rimu or ʻimu is a general Polynesian term for edible plants living underwater, such as seaweed, or plants living near water, like algae. In Hawaii, there are approximately one hundred names for kinds of limu, sixty of which can be matched with scientific names. Hundreds of species of marine algae were once found in Hawaii. Many limu are edible, and used in the cuisine throughout most of Polynesia.
Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of Rhodophyta (red), Phaeophyta (brown) and Chlorophyta (green) macroalgae. Seaweed species such as kelps provide essential nursery habitat for fisheries and other marine species and thus protect food sources; other species, such as planktonic algae, play a vital role in capturing carbon, producing at least 50% of Earth's oxygen.
Red algae, or Rhodophyta, are one of the oldest groups of eukaryotic algae. The Rhodophyta comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority of species (6,793) are found in the Florideophyceae (class), and mostly consist of multicellular, marine algae, including many notable seaweeds. Red algae are abundant in marine habitats but relatively rare in freshwaters. Approximately 5% of red algae species occur in freshwater environments, with greater concentrations found in warmer areas. Except for two coastal cave dwelling species in the asexual class Cyanidiophyceae, there are no terrestrial species, which may be due to an evolutionary bottleneck in which the last common ancestor lost about 25% of its core genes and much of its evolutionary plasticity.
Isabella Aiona Abbott was an educator, phycologist, and ethnobotanist from Hawaii. The first native Hawaiian woman to receive a PhD in science, she became a leading expert on Pacific marine algae.
Ice-ice is a disease condition of seaweed. Ice-ice is caused when changes in salinity, ocean temperature and light intensity cause stress to seaweeds, making them produce a "moist organic substance" that attracts bacteria in the water and induces the characteristic "whitening" and hardening of the seaweed's tissues. Bacteria involved include those in the Vibrio-Aeromonas and Cytophaga-Flavobacteria complexes. The bacteria lyse epidermal cells and chloroplasts, turning the seaweed tissue white. The disease is known from seaweeds including Kappaphycus alvarezii and Eucheuma denticulatum, economically important sources of carrageenan. In countries where seaweed is harvested as a crop, ice-ice can wreak havoc on yields. Zamboanga, Philippines, had an outbreak of ice-ice in 2004, and Bali, Indonesia, experienced an outbreak in 2009. A rise in surface sea temperatures of 2–3 degrees Celsius can trigger ice-ice outbreaks.
Asparagopsis taxiformis, formerly A. sanfordiana, is a species of red algae, with cosmopolitan distribution in tropical to warm temperate waters. Researchers have demonstrated that feeding ruminants a diet containing 0.2% A. taxiformis seaweed reduced their methane emissions by nearly 99 percent.
Polysiphonia lanosa is a common species of the red algae (Rhodophyta) often to be found growing on Ascophyllum nodosum.
Polysiphonia devoniensis is a species of marine algae. It is a small red alga in the Division Rhodophyta. It is a species new to science only described recently and first published in 1993.
Melanothamnus harveyi, Harvey's siphon weed, is a small marine red alga in the division of Rhodophyta.
Polysiphonia nigra is a species of marine alga in the division Rhodophyta.
Vertebrata fruticulosa(Boergeseniella fruticulosa Kylin) is a small marine alga in the Division Rhodophyta.
Hypoglossum hypoglossoides, known as under tongue weed, is a small red marine alga in the family Delesseriaceae.
Delesseria sanguinea is a red marine seaweed.
Gracilaria coronopifolia, also known as limu manauea in Hawaiian, or ogo in Japanese, is a species of edible red algae (Rhodophyta) endemic to Hawai'i.
