Alternative Methods Of Nutrient Absorption

Not all algae have chloroplasts and photosynthesize. “Colourless” algae can obtain energy and food by oxidizing organic molecules, which they absorb from the environment or digest from engulfed particles. They are classified as algae, rather than fungi or protozoa, because in most other features they resemble photosynthetic algae. Algae that rely on ingestion and oxidation of organic molecules are referred to as heterotrophic algae because they depend on the organic materials produced by other organisms.

Algae also produce many other kinds of sugars and sugar alcohols, such as rhamnose, trehalose, and xylose, and some algae can generate energy by oxidizing these molecules.