Abstract
The present chapter covers the concept of water pollution, its cause and effects on plant diversity of an aquatic ecosystem. An alteration in the diversity of plants and the disappearance of aquatic plants has been noted in the majority of the world's water bodies as a result of water pollution. In polluted aquatic ecosystems, plant diversity was studied as a strong bioindicator of water quality. Numerous studies on phytoplankton and aquatic macrophytes have been incorporated in this chapter as an indicator of water pollution. Water pollution leads to changes in species composition, declines in overall plant species diversity and the loss of rare and uncommon species. A perturbation in aquatic ecosystems causes succession of macrophytes with complete loss of submerged vegetation and dominance of phytoplanktons and weeds. Monitoring, assessment and measurement of plant diversity through density, frequency, abundance and diversity indices are also integrated in this chapter.