Part 1 – What are Algae?

Algae are primitive, mostly aquatic, one-celled or multicellular plant-like organisms that lack true stems, roots, and leaves but usually contain chlorophyll. There are both saltwater and freshwater algae, and algae are found almost everywhere on earth.

Algae grow when they have the right conditions such as adequate nutrients (mostly phosphorus but also nitrogen), light levels, pH, temperature, etc. Usually, the amount of phosphorus available controls the amount of algae found in a freshwater lake or water body. Generally, the more nutrients found in a lake, the more algae present in the lake.

Algae are also found in streams—the slippery stuff on the rocks in the water are usually algae. Although microscopic, the “slippery stuff” is a community of diatoms, algae of various types, single-celled animals, bacteria, and fungi. This community is the favorite food of many of the stream’s herbivores.

Healthy waters need algae because algae are the primary producers in the ecosystem. They use sunlight (through photosynthesis) to produce carbohydrates and are eaten by grazers such as protozoa and zooplankton (little animals like water fleas and rotifers). The zooplankton are then eaten by small fish, which are eaten by bigger fish, and on up the food chain. A productive lake or stream produces large fish and good fishing for humans as well as supporting food and habitat for wildlife and waterfowl. In this context most algae are desirable for lakes and streams.

This series about algae in our waters was written by Lake Specialist Reesa Evans of the Adams County Land & Water Conservation Department. She is also a lake manager certified by the North American Lake Management Society.