What Are the Functions of Chlorophyll and Accessory Pigments in Algae?

Light

• Light is energy composed of wavelengths. Longer wavelengths have less energy and shorter wavelengths have more energy. The longer wavelengths penetrate more deeply into the ocean. Algae tend to absorb longer wavelengths, as they penetrate deeper into the ocean water. Land plants absorb longer wavelengths predominantly, since they evolved from algae.

Chlorophyll

• Green plants use the energy from the sun to combine carbon dioxide and water to make sugar and oxygen, generating adenosine triphosphate (ATP), the fuel of all living organisms. Chlorophyll exists in all photosynthetic organisms except for bacteria.

  Chlorophylls are photosynthetic pigments that absorb certain areas of the light spectrum and reflect the color green. They contain porphyrin rings, which are stable rings of organic compounds through which electrons can move freely. This enables chlorophyll to transfer electrons to other molecules and trap the energy of sunlight for photosynthesis.

  Chlorophyll-a is the primary pigment, while the others, including chlorophyll-b, are secondary. Chlorophyll-a appears in all algae, while chlorophyll-b appears only in green algae. Chlorophyll generates energy only when it absorbs light while within a chloroplast. Otherwise, the light will turn into longer wavelengths in a process called fluorescence or will change into heat.

Carotenoids

• Accessory pigments cannot transfer energy from the sun directly, but can pass the energy to chlorophyll. Carotenoids have orange, red and yellow pigments. They have carotene, which is the substance that makes carrots orange.

Fucoxanthin

• Fucoxanthin gives brown algae its color and supplements chlorophyll photosynthesis. It functions in combination with chlorophyll, increasing the algae's efficiency. Algae with extra pigments usually reside in areas so deep that the light intensity is only 1 percent of the light intensity at the ocean surface.

Phycoerythrin

• Phycobilins are pigments in red algae. They dissolve in water and occur in cytoplasm and in the stoma of chloroplasts. There are two types: phycocyanin and phycoerythrin. Red algae have phycoerythrin and are sometimes nearly black since they can absorb most of the wavelengths in the color spectrum.