In addition the Chromista groups store energy in the form of varous oils. Green plants store enery in the form of starch. There are several groups comprising the Chromista. Diatoms are ubiquitous and occur in abundance in both fresh and marine environments. Fresh water forms are often useful indicators of environmental quality.
Most species are single-celled, although a few are weakly colonial.
Silicoflagellates are planktonic marine algae that are both photosynthetic and heterotrophic. They have an internal silica skeletons constructed of a network of bars. Silicoflagellates are much less common than diatoms, but are widely distributed throughout the oceans of the world. Silicoflagellates propel themselves by a long flagellum. The brown algae are marine and multicelluar and comprise the largest algae of the world.