Closterium moniliferum is a large green alga found in freshwater environments. Its elongated cells have a crescent or banana-like shape and are enclosed in a firm cellulose cell wall. Each cell contains multiple ribbon-shaped chloroplasts with pyrenoids for starch storage, as well as a centrally located nucleus. The alga contributes to primary production through photosynthesis and supports aquatic food webs by providing a food source for various organisms.