Algae are actually the most well known of a group of organisms called phytoplankton. Algae can best be described as small or microscopic plants. These organisms are photosynthetic, meaning that they function as plants, producing their own food from sunlight. Phytoplankton are the basis of most aquatic food chains, and are one of the primary producers of the oxygen we breathe. There are several different types of phytoplankton living in Chesapeake Bay and its tributaries. Choose from the following classifications: