Cladophora, genus of green algae (family Cladophoraceae) found growing attached to rocks or timbers submerged in shallow lakes and streams; there are some marine species. Several species, including Cladophora glomerata, are considered a nuisance in recreational bodies of water. In the Great Lakes of North America, the overgrowth of these algae has been associated with the rise of invasive zebra mussels.
Coarse in appearance, with regular-branching filaments that have cross walls separating multinucleate segments, Cladophora grows in the form of a tuft or ball with filaments that may range up to 13 cm (5 inches) in length. Asexual reproduction involves small motile spores (zoospores) with four flagella. In sexual reproduction the biflagellate gametes normally unite, although they sometimes develop into new algae without union.