The Effects of Light Color on Algae

Algae

• The term "algae" refers to a number of different organisms that have a few common characteristics. All algae are plantlike and are able to make their own food. Unlike plants, algae do not have true roots, leaves, vascular tissues or complex reproductive structures. While common green algae found growing in ponds or aquariums is the kind typically thought of when discussing algae, algae is found in many colors and can range from single-celled organisms that are microscopic in size to seaweeds that exceed 165 feet in length. These different organisms require different colors of light for best growth.

Photosynthesis

• Photosynthesis is a process in which light is absorbed by special pigments in an organism and converted into energy. While most people are familiar with photosynthesis occurring in plants, other organisms are able to convert energy via photosynthesis as well, such as algae. The most common pigments are chlorophylls, which are green and give plants their green color. Chlorophylls appear to be green because this is the wavelength that chlorophylls do not absorb; plants grow best in red and blue light because these are the wavelengths that chlorophylls absorb.

Light Color

• Many algae are able to adapt to flourish in any light wavelength. While plants typically contain only chlorophylls, and are thus limited in the colors that they are able to absorb, algae contain types of light-absorbing pigments other than green chlorophylls. Carotenoids are pigments that are red, yellow, orange and brown in color and phycobilins are iridescent red or blue. Algae are able to change the amount of the pigments they contain in order to maximize the amount of light they are absorbing from a light source. There are no colors of light that will completely prevent algae from growing.

Color of Algae

• Algae are perceived as being different colors due to their light-absorbing pigments, and algae normally use pigments that are best suited for their environment. For instance, red algae contains a pigment called phycoerythrin, which absorbs blue light and makes the algae appear red. Red algae grows deep in the ocean, and blue light wavelengths travel deeper into the water than other colors, so this pigment helps the algae absorb the most light possible. However, if algae changes its pigments to adapt to an unusual situation, the color that we perceive the algae as being will change as well.