The increasing incidence of fertilizer run-off in still bodies of water has been detrimental to desmid populations. The organisms cannot reproduce as quickly as many other forms of algae in nutrient-rich environments and tend to diminish when placed in a situation of heavy competition. Thus, due to their dependence on clear, unadulterated water, desmids have become rare in many parts of the world. However, as a consequence of their stringent environmental demands, the organisms are very useful in monitoring the conditions of aquatic habitats.