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Rhodophyta: Red algae

Examples: Palmaria, Coralline algae

Characteristics: The red colour of these algae results from the dominance of the pigments phycoerythrin and phycocyanin; this masks the other pigments, Chlorophyll a (no Chlorophyll b), beta-carotene and a number of unique xanthophylls. The main reserves are typically floridean starch, and floridoside. and true starch is absent. The walls are made of cellulose and agars and carrageenans, both long-chained polysaccharide in widespread commercial use. There are some unicellular representatives of diverse origin; more complex thalli are built up of filaments.

A very important group of red algae is the coralline algae, which secret calcium carbonate on to the surface of their cells. Some of these corallines are articulated, with flexible erect branches; others are crustose. These corallines have been used in bone-replacement therapies.Coralline algae were used in ancient times as vermifuges.

Several red algae are eaten: best known amongst these is dulse (Palmaria palmata) and Carrageen Moss (Chondrus crispus and Mastocarpus stellatus). However, Nori, popularised by the Jananese is the single most valubable marine crop grown by aquaculture with a value in excess of US$1 billion. More information.

The red algae Kappaphycus and Betaphycus are now the most important sources of carrageenan, a commonly used ingredient in food, particuarly yoghurts, chocolate milk and repared puddings. Gracilaria, Gelidium, Pterocladia and other red algae are used in the manufacture of the all-important agar, used widely as a growth medium for microorganisms and for biotechnological applications.

There are about 6500 species of red algae, most of which are marine. These are found in the intertidal and in the subtidal to depths of up to 40, or occaisonally, 250 m.

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