The impact of alien invasive plants on water quality

• Alien plants are plants that are intentionally or accidentally brought to an area outside their natural habitat or country where they then establish themselves.
• Due to the absence of their natural enemies or diseases in their new habitat, as well as the fact that they are resilient and reproduce quickly, invasive plants are often more successful than indigenous plants that belong to that area.
• Alien plants that flourish, successfully crowding and out-competing indigenous plants, are known as invasive plants
• An example of alien invasive plants that threaten water quality in freshwater sources such as lakes, dams and slow moving rivers, is the water hyacinth. (Eichhornia crassipes)
• Water hyacinths are floating water plants with bright green leaves that grow in the form of rosettes
• Water hyacinth has distinctive swollen leaf stalks (petioles) and light purple or blue flowers
• The plants reproduce quickly and form a carpet-like cover on the water surface
• This blocks sunlight from other photosynthetic organisms (aquatic plants) in the deeper layers of the water. This causes the death of many aquatic plants
• The dead plant material decomposes, leading to a drastic increase in decomposition bacteria
• Decomposition bacteria use large amounts of oxygen during the process of decomposition.
• Less oxygen is available for other aquatic organisms, causing many of them to die
• The dense, carpet-like plant mass also clogs waterways, irrigation pipes and canals
• Alien plants that block up waterways may also impact on the supply of water to purification plants.
• The stagnant water also increase the risks of water-borne diseases
• Possible actions against invasive plants

  • Create awareness of the negative impact of alien plants
  • Remove alien vegetation using mechanical, chemical and biological control
  • Encourage the planting of indigenous plants