Alicia Accardo, age 11, of Barrington Hills, I11., for her question:
HOW DOES ALGAE GROW?
All algae contain chlorophyll. The plants help to purify the air and water by a process of photosynthesis. Algae are also food for fish and other creatures that live in the water. Some grow best in polluted water and when waste material is dumped into fresh water by man, algae will often increase and upset the natural balance of life in a body of water.
Algae are actually simple organisms that live in ponds, lakes, oceans or rivers. A single one is called an alga. Some algae are large plants while others are just single cell plants.
One type, called the blue green algae, takes the form of slippery coatings on rocks along creeks, rivers and lakes. Most of this type reproduce and grow only by cell division.
Other algae, often grouped as brown, green or red, grow and reproduce by cell division although most of them can also reproduce sexually.
One of the most plentiful of the brown algae is found on the shores of oceans in most temperate zones. Called kelp, it can grow to be 200 feet long. Algin, a substance obtained from kelp, has been used in food products and also cosmetics. It was also used at one time as a source for iodine.
Green algae are found in both fresh and salt water with most of them living in lakes and ponds. Large amounts have been known to color an entire lake. For the most part, green algae are microscopic although other species, primarily those found along ocean fronts, can be longer. On many coral beaches green algae consist of long pieces of seaweed filled with lime.
Red algae are found chiefly in subtropical areas and on coral beaches. A few species are found in fresh water. Some of the red algae contain agar, a gelatin like substance used by scientists to grow bacteria in laboratories.
Some people in Japan use red algae as a food item. It is called nori and it is sold in dry sheets.
Botanists list blue green algae in the same familyas bacteria, but they consider all other types to be plants.
Most blue green algae can only be seen with a microscope because they are so small. Some of the species have only one cell while others form into strands. Cells of this type of algae lack a distinct nucleus. Besides chlorophyll, they also contain blue or red pigments, the combination often giving them a pinkish, brown or black look.