Phytoplankton are microscopic autotrophic aquatic organisms that derive their nutrition from photosynthesis. Groups of freshwater phytoplankton include algae (green, yellow-green and golden-brown), cyanobacteria (blue-green algae), diatoms and dinoflagellates. Phytoplankton can be unicellular, colonial, or filamentous. These organisms have limited mobility that is based on water movements; however, some are able to move via flagella. An aquatic habitat will generally contain an assemblage of phytoplanktonic species that vary in proportion over time and space. As the base of the food webs, phytoplankton plays a significant role in the bioaccumulation of contaminants. The goal of the ‘Phytoplankton’ model is to dynamically simulate the bioaccumulation of organic contaminants and metals in phytoplankton.