In polluted water, Eichhornia crassipes proliferates rapidly, forming a single compact straw mat, which obviously reduces the light transmittance of the water, thus limiting the photosynthesis of phytoplankton, submerged plants and algae in the water, and the diversity of aquatic plants may be affected. At the same time, animals and plants in the water consume a lot of oxygen and increase the content of carbon dioxide. The growth and reproduction of Eichhornia crassipes make the humus in water increase, the pH value decrease and the color of water change. Due to the increase of Eichhornia crassipes biomass, dense grass mats slow down the flow velocity, and the undegraded plant debris at the bottom of the river increases, which gradually deposits in the water body, leading to riverbed uplift. The change of physical and chemical factors in water, especially the decrease of oxygen content in water and the decrease of underwater plant and animal breeding places will lead to the decline of animal diversity in water. However, by comparing the Eichhornia crassipes community in Lake Victoria, Uganda, Masifwa et al. found that the diversity of aquatic invertebrates decreased from the open water near Eichhornia crassipes community to the sedge community near the shore. They thought that Eichhornia crassipes increased the diversity of aquatic invertebrates in open waters, and he also established the optimal width model of Eichhornia crassipes population growing on the shore in an attempt to increase the diversity of aquatic animals. Bailey and Litterick believe that when the density of Eichhornia crassipes is low, the diversity of aquatic animals may increase, but when the density of Eichhornia crassipes increases, the diversity of aquatic animals and plants will decrease.

The dense growth of Eichhornia crassipes in water often leads to the decrease of submerged aquatic plants, but due to its massive siltation for many years, the silt in the riverbed deepened, and the emergent aquatic plants such as reeds and wild water bamboo increased in large numbers. At the same time, these emergent plants can prevent Eichhornia crassipes from drifting, so that Eichhornia crassipes can settle in large numbers and multiply and grow rapidly. They complement each other, greatly affecting the river landscape and blocking the river.

Due to the invasion of Eichhornia crassipes, the inherent food chain structure of the local river ecosystem has been changed, which has affected the normal growth and reproduction of fish. In some rivers and lakes in Africa, there is plenty of oxygen and food near the riparian vegetation and open water, which is the place where many fish breed, grow and inhabit. However, the invasion of Eichhornia crassipes often hinders the migration of fish, which in turn affects the reproduction, feeding and growth of young fish.