Fragilaria construens is a species of diatom, a single-celled algae with silica cell walls. It is characterized by its elongated, rectangular cells forming ribbon-like colonies. Found in freshwater environments, this species is a crucial primary producer and contributes significantly to aquatic ecosystems. Diatoms like Fragilaria construens are used as bioindicators to monitor water quality and assess historical environmental conditions through their fossilized remains. Their unique silica frustules also make them important in scientific research.