In Spirogyra, gametesare non-motile and sexual reproduction takes place by conjugation. Sargassum belongs to phaeophyceae, which contains chlorophyll a and chlorophyll c. Basidiomycetes includes puffballs, mushroom etc. Nostoc is a colonial cyanobacteria, which causes algal bloom. Related Theory Since blue-green algae are prokaryotes, they are not currently included under algae (because all algae are classified as eukaryotic organisms). These organisms live in moist or aquatic environments just like other algae. They obtain energy through the process of photosynthesis. Ecologically. some species of blue-green algae are significant to the environment as it fixes the nitrogen in the soil. Hence, these are also called nitrogen-fixing bacteria. E.g. Nostoc, Anabaena, etc.