Forest Preserve District of Cook County, Illinois
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Nature Bulletin No. 556-A   March 1, 1975
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

These are the most exciting years that mankind has ever known -- the beginnings of the Space Age. Already, earthlings are making definite plans to visit the moon and Mars and even more distant parts of the universe. Because of the enormous amounts of fuel and equipment necessary for each pound of pay load to escape the earth's gravity and return, the supply of food and oxygen for travelers on these fantastically long journeys must be kept to a minimum.

One of the suggested answers is to make use of the microscopic alga, Chlorella, which is found commonly in fresh water. In sunlight, like other green plants, it uses carbon dioxide and plant foods to grow and multiply. In the process it releases pure oxygen which could be used for breathing. Furthermore, a crop of excess Chlorella -- rich in food value -- could be harvested to feed the human passengers. They, in turn, produce the carbon dioxide and waste materials necessary to keep the alga growing. Such a miniature world can be imitated in a sealed glass container of water stocked with a bit of alga and a little aquatic animal life. Set near a window, they often survive for years.

Algae lack true leaves, stems, roots and flowers but they are perhaps the most widespread and diverse of all plants. Extremes are the rule. Among the many thousands of known species, they vary in size from microscopic single cells up to the 1500-foot long vine kelp, the longest of living things. Some can grow on snow in arctic regions and stain it red; others thrive in the hot springs of Yellowstone Park at temperatures up to 167 degrees F. Most kinds live in water -- either fresh, brackish or salt -- yet many live out of water. Algae contain chlorophyll and can manufacture their own food; but, in some large groups of them, such as the seaweeds, their green color is masked by other pigments so that they appear yellow or brown or red.

Common local examples of algae are the scum on lakes, ponds and streams during "Dog Days" in late summer. Several kinds of these form blankets of tangled slender threads that trap and hold enough bubbles to buoy them up. The so-called "water blooms" are finely divided scum made up of single-celled algae or minute capsules of jelly enclosing a tiny colony of them. Along the leeward shore of a pond or lake these floating blooms sometimes pile up so thick that they look as if a bucket of green or red paint had been spilled. On land, other algae form the thin green coatings on soil, rocks, and the trunks of trees -- usually on the shaded north side.

The brown slimy masses seen in streams and on water plants in early spring are made up of millions of single-celled algae called diatoms. Each minute diatom is enclosed in a two-parted shell -- a glass box made of silica -- which is engraved with a delicate pattern of perforations so perfect that they are used to standardize scientific instruments. Over the ages, huge deposits of these shells have accumulated in certain places and, as "diatomaceous earth, " are mined for various purposes such as the abrasive in toothpaste.

Algae are the basis for existence of practically all animal life in water. They are the first link in the chain which combines sunshine and simple dissolved substances in plants that animals can eat. The fish that you catch and eat -- a black bass for example -- fed on minnows, crayfish, and aquatic insects. Those fed on tiny crustaceans, still smaller insects and water worms. These fed on a host of still smaller water animals and they, in turn fed on algae. Some food chains are longer and some are shorter, but they all start with algae.

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