Red algae or Rhodophyta, as they are known botanically are one of the oldest groups of eukaryotic (nucleus) algae, and also one of the largest, with about 5,000 – 6,000 species. These are mostly multicellular marine dwellers and most of the world’s seaweeds belong to this group. The Corraline group build up calcium carbonate in their cell walls, and can also be reef-building organisms.
Red algae are able to photosynthesise at greater depths than both green and brown algae and are, therefore, more abundant in deeper waters. The redness is due to the presence of a pigment called phycoerythrin. This pigment reflects red light and absorbs blue light. The blue light penetrates deeper into the water than light of longer wavelengths, and it is because of these pigments that they are able to photosynthesize at greater depths. Like the other groups, red algae provide food and shelter for a range of marine animals.
Although many people don’t generally consider these organisms as economic producers, there are some important uses. For this reason, extensive farming and natural harvest of red algae occurs in numerous areas of the world. For instance:
Agar has been used for years in microbiology, as it provides a polysaccharide gel which is solid, and nontoxic, yet cannot be digested by most microorganisms. Agar-agar is also a delicacy in Japan and it is a clear, jelly-like food, and is virtually flavourless and indigestible.
Aarose is purified from agar and is a mainstay of molecular biology, an alternate to polysaccharides and can be sold at great expense.
Japanese nori is said to be the single most valuable marine crop grown by aquaculture and used for wrapping sushi, rice crackers, topping on rice, etc. The high vitamin and protein content of this food makes it attractive, as does the relative simplicity of cultivation, which began in Japan more than 300 years ago. The growing of nori is a substantial industry with a market value of around US$2 billion.
Dulse is eaten and used as medicine in Ireland, Iceland and Atlantic Canada. In these regions you are likely to find it in health food stores or at fish markets. A variety of dulse is cultivated in Nova Scotia and marketed as Sea Parsley, sold fresh in the produce section. Dulse is also shipped around the world.
Chondrus crispus is grown commercially for the extraction of carrageenan (Irish Moss) which is commonly used as a thickener and stabilizer in milk products such as ice cream and processed foods including lunch meat like those seen above. The organism may also be used as a thickener in calico-printing and to clarify, or fine beer or wine.
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