Forest Preserve District of Cook County, Illinois
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The Seaweeds
Nature Bulletin No. 702   January 26, 1963
Forest Preserve District of Cook County
Seymour Simon, President
David H. Thompson, Senior Naturalist

As the number of people in the world increases and the number of acres of fertile soil to produce food for them decreases, man looks more and more hopefully at the huge expanses of ocean for relief from hunger. For ages, fish and other sea foods -- including Seaweeds -- have been mainstays in the diet of seafaring peoples, islanders and coast dwellers. Even in the Middle West we are accustomed to eating saltwater fish and shellfish. Seaweeds, however, are not seen on the vegetable counters of our stores but, unsuspected by most of us, products of seaweeds are found in many of our foods, medicines and articles in daily use.

Most seaweeds grow attached to underwater rocks, reefs and the sea bottom down to depths of 100 feet or more. Although many of them vaguely resemble flowering plants in size and shape, they do not have true roots, stems, leaves or flowers. Instead, they are members of that great group of lower plants called the Algae and should not be confused with the submersed vegetation in fresh waters, which is sometimes mistakenly called "seaweed".

The Kelps, largest of the Brown Algae, thrive best in cold water. The Giant or Vine Kelp with a slender stem anchored to a holdfast in deep water is reported to reach lengths as great as 1500 feet, making it the longest plant in the world. Along this stem are many yard-long leaf-like blades buoyed up by egg-sized floats like stockings hung on a clothesline. Other kinds of kelp, each with its distinctive shape and habit of growth, have such colorful names as Devil's Apron, Fan Kelp, Bull Kelp and Ribbon Kelp.

The Sea Mosses, members of the large group of Red Algae, are delicate cylinders, sheets, ribbons or feathers seldom larger than a man's hand. Many are found in deep water where their red pigment enables them to grow in dim light. The Japanese cultivate certain kinds on bundles of bamboo in underwater farms. Others are the source of agar used as a laxative and to make the jelly on which bacteria are grown in laboratories. Puddings are made from Irish Moss and St. Patrick's soup from another kind called Dulse.

Seaweeds are rich in many minerals and vitamins necessary for human health. They add bulk to the diet but are rather poor in fats, carbohydrates and proteins. Formerly, they were an essential source of iodine and potassium. More recently an industry in California, using mechanical harvesters mounted on barges, processes kelp into a number of useful products. Among these is a substance called "algin" which gives body to other substances. It prevents the chocolate from dropping to the bottom of your chocolate milk and keeps your ice cream from rapidly melting into a puddle. n is used in shaving cream, shoe polish, lipstick, shampoo, cosmetics, lubricating jellies and as sizing in cloth.

Kombu is a food prepared from seaweed by the Japanese for use in soups, on meat and rice, or nibbled after crisping over a fire. As a result, because of its iodine content, goiter is almost unknown there. In the Scandinavian countries and the British Isles, herdsmen near the coast feed seaweed to their cattle or graze their sheep on it at low tide. In Ireland potato fields are fertilized with kelp.

In 1492 Columbus sailed into a vast expanse of floating seaweed, much to the terror of his men who imagined that this was the legendary graveyard of becalmed ships. This Sargasso Sea, with its unattached Gulf Weed, covers an area as large as the United States, extending half way across the Atlantic east of Florida and the West Indies.

Some sea serpents may be nothing more than large kelp seen in dim light by sailors after a night in port.

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