coralline algae


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Rhodophyta

Rhodophyta (rōdŏfˈətə), phylum (division) of the kingdom Protista consisting of the photosynthetic organisms commonly known as red algae. Most of the world's seaweeds belong to this group. Members of the division have a characteristic clear red or purplish color imparted by accessory pigments called phycobilins, unique to the red algae and the cyanobacteria. The chloroplasts of red algae are believed to be derived from cyanobacteria that formed an ancient symbiotic relationship with the algae.

Of the approximately 4,000 known species of red algae, nearly all are marine; a few species occur in freshwater. Although red algae are found in all oceans, they are most common in warm-temperate and tropical climates, where they may occur at greater depths than any other photosynthetic organisms. The red algae are multicellular and are characterized by a great deal of branching, but without differentiation into complex tissues. The red algal cell wall has a firm inner layer containing cellulose and a mucilaginous or gelatinous outer layer. Cells may have one or more nuclei, depending on the species. Cell division is by mitosis. The red algae are remarkable in that they are not flagellated; none has motile cells of any kind.

Cells of the Rhodophyta possess chloroplasts that, in addition to the phycobilins, contain chlorophyll a, carotenes, and xanthophylls. At great ocean depths, where the wavelength of light available for photosynthesis is very different from that in shallow water, the phycobilins become more active than the chlorophylls in absorbing light; this fact may explain the ability of red algae to exist at depths of up to 879 ft (268 m). The carbohydrate reserves of red algae are in the form of floridean starch, a specialized glucose polymer of different structure than the starch of plants.

The life cycle of the red algae is extremely complex, involving one haploid phase and two diploid phases. Most marine red algae have soft and delicate bodies, or thalli; however, the coralline algae have thalli that become strongly calcified and contribute significantly to the growth of coral reefs in tropical seas. Because of the permanent nature of the structures that they produce, coralline algae have a rich fossil record that extends back as far as 700 million years. Commercial agar, used as a culture medium for bacteria and other organisms as well as for other purposes, is produced from several genera of red algae. The so-called Irish moss is the source of carrageenin, a substance widely used as a stabilizing agent in emulsions and in ice cream.

Bibliography

See H. C. Bold and M. J. Wynne, Introduction to the Algae: Structure and Reproduction (1985); C. A. Lembi and J. R. Waaland, Algae and Human Affairs (1988); C. van den Hoek, Algae: an Introduction to Phycology (1994).

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coralline algae

[′kär·ə‚lēn ′al·jē]
(botany)
Red algae belonging to the family Corallinaceae.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The New Zealand abalone is among those invertebrate larvae that depend directly on the presence of crustose coralline algae. Commonly known as paua, it is a key coastal species, given its huge economical, ecological and cultural importance.
Morse (1990) presented evidence that abalone larvae require exogenous chemical induction for settlement and metamorphosis, and Morse and Morse (1984) suggested that settlement cues associated with crustose coralline algae are related specifically to certain chemicals produced by them and present only on their surfaces (Morse 1992).
Negri, "Crustose coralline algae and a cnidarian neuropeptide trigger larval settlement in two coral reef sponges," PLoS ONE, vol.
Luminaolide, a novel metamorphosis-enhancing macrodiolide for scleractinian coral larvae from crustose coralline algae. Tetrahedron Lett.
In the case of the 1982-83 El Nino, the recovery was limited by 1) the extreme oceanographic conditions of the region, 2) the high coral mortality suffered during the El Nino, 3) the intense herbivory resulting from high sea urchin concentrations produced high rates of bieorosion, 4) low abundance of recruits due to reduced sexual activity of the main reef builder species, and 5) low potential for successful recruitment due to the low abundance of crustose coralline algae (Guzman & Cortes 2001).
The following were identified with varying depth: Sponges, echinoderms, pelecypods, bivalves, coralline algae and foraminifera Globorotalia cerroazulensis.
Each transparency represented a 0.25 [m.sup.2] quadrat that was evaluated by projecting onto a grid containing 25 random points (modified point quadrat) and evaluated based on (1) Bare Substrate, (2) Cyanobacteria, (3) Green Algal Mat, (4) Red Algal Mat, (5) Coralline Algae, or (6) Live Coral coverage.
A tiny human backbone comes to mind, rather than a piece of coralline algae. Moving it gently with a forefinger, a person can discover that the jointed segments are quite flexible.
Similarly, their association with coralline algae, coral fragments, gymnocodiacean and udoteacean algae and echinoderms in the Cuautla Formation also indicates normal salinity (Flugel, 1982).
He says the discovery of rhodoliths in Alaska marks an important milestone in scientists' understanding of coralline algae.
Another good buy is Versace's Lips (pounds 15), a range of lipsticks containing Vitamin E and trehalose - which helps protect lips from dryness - and coralline algae which aims to help control skin ageing.