Algae can grow in virtually any environment that possesses carbon dioxide, sunlight, minerals and sufficient water. Algae are very simple organisms that share many traits with plants, although most scientists exclude algae from the same classification with advanced plants. Algae lack the vascular structures common to other plants, so they must live in areas with adequate moisture.
Algae are photosynthetic organisms that manufacture their own food by harvesting the power of sunlight. Algae must combine the sunlight with photosynthetic cells, carbon dioxide, minerals and water to create sugars. Algae usually have abundant water and carbon dioxide in their environment, and the limiting factor is often sunlight or minerals. This explains why algae populations may sometimes explode when the sunlight levels or mineral content of a body of water change.
Algae are common in many aquatic habitats. Algae grow in ponds, lakes, rivers, streams, creeks, puddles, water reservoirs and waterfalls. However, algae also grow in very damp, yet not aquatic, habitats. For example, the rocks surrounding a creek or river may be damp enough to support a lush carpet of algae. Damp caves and other situations may also be damp enough to support algae growth. Rainforests are occasionally damp enough to support algae on the trunks of trees.