Diatoms rely on the process of photosynthesis to make food, although a few diatom organisms may rely on floating nutrients found in their habitat. Photosynthesis is the process of taking sunlight and turning it into energy by storing it as a carbohydrate. The diatom releases the energy, which acts as a food source for the organism.

Because diatoms use photosynthesis to produce food, these organisms are responsible for providing energy to the ocean's ecosystem. Small animals that feed on plankton rely on nutrient rich diatoms for survival. Diatoms do not survive when there are major changes within its habitat, and most diatoms exist in extremely cold oceanic waters.