Ans. As desmids can grow only in freshwater, they act as an important indicator for identifying water quality. It shows the information on aquatic environmental conditions like pH, conductivity, and trophic state of the aquatic body. The chlorophyll present in desmid algae absorbs the dissolved carbon dioxide and releases oxygen during photosynthesis. This helps to provide oxygen to aquatic organisms. The desmid acts as food for many aquatic species.