Veli-Akkulam Estuary

News: The Veli–Akkulam estuary is gradually degrading as invasive species, pollution, urban runoff, and encroachment are disrupting its food web and reducing native biodiversity.

About Veli–Akkulam estuary

• Location: The Veli–Akkulam Estuary is located on the Thiruvananthapuram coast, Kerala.
• It is a small, shallow, and bar-built estuary that forms part of the Kerala backwater system, adjoining the Lakshadweep Sea. 
• Structure: The estuary is divided by a man-made bund into two separate sections:
  • the western Veli Estuary
  • the northeastern Akkulam Estuary
• Its connection to the sea is not permanent and occurs intermittently during the monsoon season through the natural breaching of a coastal sandbar.
• Reasons for degradation:
  • Proliferation of invasive species: The estuary is now being largely dominated by invasive species.
    • Native fish like the prized karimeen (Etroplus suratensis), barbs, and indigenous catfish have declined. Meanwhile, invasive species such as Mozambique tilapia (Oreochromis mossambicus) and Nile tilapia (Oreochromis niloticus) have increased rapidly, outcompeting native fish for food and habitat.
  • Trajectory of ecological decline: The estuary is gradually moving toward “a clear path of ecological decline”, shifting from a balanced ecosystem to one that is simpler and less stable. This is known as trophic simplification.
    • It means the food web is becoming shorter, less diverse, and less interconnected.
  • Drivers of degradation: As a temporarily closed system, the estuary frequently experiences limited water exchange and low oxygen levels, further promoting excessive algal growth and organic buildup.
    • In addition to these natural constraints, it is increasingly affected by human-induced activities such as encroachment into catchment areas and discharge of pollutants into the body and other streams connected to it. 
    • Water quality has also declined due to rising nutrient loads, organic pollution, and contamination from heavy metals originating from both point and diffuse sources.