Anaerobic ammonium oxidation (anammox) is a biological process in which certain microorganisms can convert ammonium ions and nitrite into dinitrogen gas under anaerobic conditions. This process plays a crucial role in the nitrogen cycle of aquatic ecosystems, particularly in marine environments, where it serves as an important nitrogen removal mechanism. Anammox bacteria are capable of performing this process by using nitrite as the electron acceptor, instead of oxygen. This unique metabolism allows them to thrive in oxygen-depleted environments, such as deep sea sediments and oxygen minimum zones in the ocean. Research in anaerobic ammonium oxidation aims to further understand the metabolic pathways, ecological significance, and environmental implications of these microorganisms. By studying anammox bacteria, scientists hope to develop more efficient strategies for removing nitrogen from wastewater and controlling nitrogen pollution in aquatic systems.