Chrysophytes, or golden algae, are common microscopic chromists that live in fresh water. Some species are colorless, but the vast majority are photosynthetic. These organisms are particularly important in lakes, where they may be the primary source of food for zooplankton. They are not considered truly autotrophic by some biologists because nearly all chrysophytes becom facultatively heterotrophic in the absence of adequate light, or in the presence of plentiful dissolved food. When this occurs, the alga may turn predator, feeding on bacteria or diatoms. There are more than a thousand described species of golden algae, most of them free-swimming and unicellular, but there are filamentous and colonial forms. Other chrysophytes may spend part of their life as amoeboid cells.