Where algae grow

There are almost 27,000 different kinds of algae. They can be found throughout the Earth, in oceans, rivers, lakes, streams, ponds, and marshes. Algae are usually found in water and in moist places. However, some live in dirt and deserts. These algae can survive dry conditions for a long time. Algae also grow on leaves, wood, and stones.

Some algae live in places where it is difficult for other living things to survive. For example, there are species of algae that live in and around hot springs that can reach a temperature of more than 170° F (77° C). A small number of algae live in the snow and ice of the Arctic and Antarctic regions. Seaweeds live anchored to the sea bottom or on solid structures. Algae even grow on animals such as turtles, polar bears, and tree sloths.

Physical features

Although some algae, such as seaweeds, look like plants, they are actually very different. Unlike plants, algae do not have stems, leaves, or true roots. Some algae have structures that attach the algae to surfaces. However, these structures do not draw out nutrients like the roots of plants do. Algae also do not produce flowers or seeds. Algae can be green, blue, red, or brown.

The size of algae varies greatly. For example, the tiny Micromonas is 0.00004 inch (1 micrometer) in diameter while the giant kelp reaches 200 feet (60 meters) in length.

Internal structure

The internal structure of algae can range from one cell to millions of cells. However, one-celled algae still perform the same functions as many-celled alga. These functions may include movement, photosynthesis, and reproduction.

Food habits

Like plants, most algae manufacture their own food through a process called photosynthesis. In this process a chemical called chlorophyll captures light and converts its energy to food. The chlorophyll also gives many plants and algae their green color. Some algae use other substances in addition to chlorophyll to absorb light. These other substances give the different algae distinct colors. A few algae get food by absorbing material from the environment.

Reproduction and growth

Algae reproduce sexually and asexually. In sexual reproduction, the algae produce sex cells called gametes. A male and a female gamete must come together to create the cell of the new alga. Asexual reproduction does not involve gametes. Instead, the cells of the algae divide and produce new algae. In larger algae a section sometimes breaks away to create new algae.

Most algae live for days, weeks, or months. Some small algae are active only at certain times of the year. Some large species that are attached to other bodies live throughout the entire year. These algae may lose their main body at the end of the growing season. However, the attachment site, or holdfast, produces new growth at the beginning of the next growing season.

Importance

Algae play an important role in the world. In fact, algae are necessary to all life on Earth.

Harmful effects

Although algae provide many benefits to people, they can also be harmful. Certain algae produce toxins, or poisons, that enter shellfish and fish. Animals and humans can be poisoned by eating these creatures. Gymnodinium breve is one such poisonous alga. It forms along the shores of the Gulf of Mexico and the Atlantic coast of the United States. In addition to poisoning fish it can harm humans in another way. The wind may blow its poisonous cells to shore. People and animals that inhale these cells can suffer from breathing difficulties. Large collections of these harmful algae are known as red tides because some of the algae contain reddish pigments. When these species reach high concentrations, the water appears to be colored red.