Diatoms are microscopic algae that are found in both fresh and salt water habitats. These are photosynthetic algae with a heavily silica impregnated cell walls. The living diatoms are amongst the most abundant forms of plankton and form an essential part of the food chain in the ocean. Diatoms prefer cool nutrient rich water and therefore the maximum biomass of the living diatoms are found in coastal regions and upwelling zones.