'KelpWatch' - Monitoring Giant Kelp Forests in Tasmania
Photo by: Jon BryanPhoto by: Jon BryanPhoto by: Jon BryanPhoto by: Jon Bryan

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Commerical Giant Kelp Harvesting


Giant Kelp (like other kelps) also have a capacity for some of the most remarkable growth rates in the plant kingdom - in southern California, Macrocystis plants can grow up to 50cm a day. These extraordinary growth rates, and their known industrial and pharmaceutical benefits, have resulted in the world-wide commercial harvesting and exploitation of Giant Kelp forests both, in Tasmania (eg. east coast) and overseas (eg. California). In the USA, M.pyrifera is harvested from large offshore beds off the coasts of California and Mexico. Some 120,000 tonnes wet weight are gathered each year using ships equipped with cutting machinery.

The first use of Giant Kelp on a large commercial basis was in California, for the purpose of producing potash (potassium carbonate) during the First World War. At the time, potash was a necessary ingredient in the production of gunpowder. The potash was derived from the kelp ashes after it had been burned. At that time, kelp was harvested by encircling a stand of kelp with a cable and then pulling on the cable. This generally had the effect of ripping out the entire kelp plant, including the holdfast. By comparison, today's harvest methods are limited to cropping the fronds, which are short-lived compared to the holdfast.

Kelp that is harvested in California today is primarily used in chemical industrial applications. Algin, which is a product derived from kelp, is used as an emulsifier in processed foods and other products where a smooth texture is required (eg. paints, cosmetics, pharmaceuticals). Other uses of kelp are as food for cultured abalone, and as substrate for the herring-roe-on-kelp fishery (exported for Sushi).

Alginates are cell-wall constituents of brown algae (Phaeophyta). Alginates of one kind or another seem to be present in most species of brown algae but they occur in exploitable quantities (30-45% dry weight) only in the larger kelps and wracks (Laminariales and Fucales). Alginates are extracted chemically and used in bulking, gelling, and stabilizing processes. Products using alginates include charcoal briquettes, cosmetics, ceramics, cheese, paint, asphalt, rubber tires, polishes, toothpaste, ice cream, and paper. About 25,000 tonnes of alginic acid per annum are extracted world-wide. The main producers are Scotland, Norway, China and the USA, with smaller amounts being produced in China, Japan, Chile, France and Spain.

Check out the following websites for further information on the uses of alginates and Giant Kelp:





Photo by: Mike Guiry
Lammiaria digitata
(Photo by: Mike Guiry)

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Enquiries and feedback: Karen.Edyvane@utas.edu.au
URL: http://www.geol.utas.edu.au/kelpwatch/   Last modified: 10. December 2001