Bright field light micrograph of filamentous green algae attached with rhizoids to red algae from the Baltic Sea. Algae is usually differentiated based on pigments; red algae contains the pigment phycoerythrin. It is abundant in marine habitats. There are approximately 6,000 species of predominantly marine algae, often found attached to other shore plants. Filamentous green algae are characterised by long, thread-like filaments, often forming dense mats. They are commonly found in various aquatic environments like ponds and lakes. Diatoms are a type of single-celled photosynthetic algae. They form a significant portion of the Earths biomass, generating about 20 to 50 percent of the oxygen produced on the planet each year. Magnification: 372x when printed 10 centimetres wide.