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This report applies the case study approach to seven of the more important and diverse world seaweed resources, to bring out some of the main factors affecting their rational production. Less emphasis is placed here on the ultimate uses of seaweeds, which range from their utilization in human food and animal foodstuffs, to their roles as food additives, in water purification systems, pharmaceuticals and as a source of biomass for power production among many other uses.

The editors are conscious of the fact that the seven case studies made available to us within the constraints of the present co-operative study do not cover all of the main types of seaweed resources of importance to man: for example, the production of seaweeds for direct human consumption especially in Japan and China is best represented here by the study on the Chinese Laminaria industry, but some of the economically most important resources are destined for other uses than directly as food. The problems faced on the production side are broadly similar in most cases however, and are likely to be addressed with some modification in one or other of the seven studies presented here.

As human populations increase and strive for better things in life, markets are created for more and more food and the luxury accoutrements of modern society. Among them are many products that require such hydrocolloidal materials as seaweeds produce. These materials are largely suspensoids which tend to keep finely divided particles or droplets separated and in suspension in liquids as in foods that are prepared by suspension in milk or water. As gels they may do the opposite; i.e., keep water suspended in solids, as in the preparation of ice-cream where the result is microcrystals in place of the sandy mouth feel of some ice-creams lacking them. They prevent the scorched taste characteristic of older forms of condensed or evaporated milk. They make many confections, foods and other modern substances possible such as cake icings that don't melt or become sticky at ambient temperatures.

The release of medicines by pills that burst only at the appropriate place as they pass through the intestinal tract are often the result of appropriate coatings of algal materials. Of algal origin are some of the world's most effective antihelminthics. Algal hydrocolloids provide the substratum for many horticultural abd biotechnological procedures such as coating seeds with pesticides and fertilizers and such as used in tissue culture, cytoplast fusion and other genetic mechanics. They produce substances that seem to be effective against some of today's most aggravating viral infections and much more.

Traditionally the seaweed of commerce has been produced from harvesting wild crops. As demands for seaweed have grown, their production by farming has proven attractive for its reliability in respect to quality and volume as well as lower costs. Thus we see the wild crops of Chondrus crispus and Laminaria longicruris, which have contributed so much to the history of seaweed use in the Western Hemisphere, being replaced by the farmed crops from other species in the Orient and Old World Tropics and by other wild crop species from the lower labour cost areas of the Southern Hemisphere. In the case of Eucheuma. shifting from wild cropping to farming has largely involved the same people in the same geographic areas and economic levels; so the change has been welcomed.

The reader will note that there is a wide range of sophistication in respect to the production of the different genera. Gelidium (and most all other agar sources but Gracilaria) is strictly still from wild crops with recognition of clear chemical differences in the agar from the different species involved, though there is little published knowledge of these differences. Our understanding and management of Ascophyllum and, even more so, Macrocystis. wild crops almost approach farming but without great concern in the literature for quality or yield of the hydrocollooid product. Yet the quality of the alginate from different genera and seasons is of primary concern to manufacturers.

Each of the seven seaweed chapters began with the same outline, but as the nature of the production of each is so very different, each chapter has come to have some unique features. However, the basic approach has been to provide the reader with the classical knowledge from science first, then the more experimentally developed specifics leading to crop management and, finally, utilization. The sequence is roughly that of the following ten numbered sections:

1 - Identity of the crop
2 - Distribution, ecology and metabolism
3 - Life history
4 - Population structure and mortality
5 - Productivity of the resource
6 - Method of harvesting and harvesting cycle
7 - Equipment used for harvesting of the resource
8 - Protection and management of the resource
9 - Utilization, processing and economics
10 - References

We hope that the provision of the available information in the above outline will tend to illuminate the gaps in the present information while providing that publicly available for these seven seaweeds. Thus the purposes include encouraging readers to fill the obvious gaps in the technology, to undertake research toward improving present practices and to write new case studies for others of the 25-odd seaweeds of importance in world commerce today.

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