River Dolphins go missing in Sunderbans as water salinity rises

River Dolphins go missing in Sunderbans as water salinity rises

News:

Population of Ganges River Dolphin on the decline due to Rise in salinity in the water system in Indian Sundarbans.

Important Facts:

• Sighting records in the study reveal that distribution of GRD (Ganges River Dolphin) is influenced by the salinity level of the waterways.
• According to research, unique body shape of Dolphins doesn’t allow them to remain submerged in waters with high salinity.

Salinity in this deltaic system is influenced by the combined action of the following factors:

• Hydrological modifications like water diversion and commission of large barrages upstream have had a great impact on the salinity profile of the rivers downstream in the Sundarbans.
  • Significant increase in salinity levels were documented in the river Ganges in India after the commissioning of the Farakka Barrage.
• Natural salinity level of the rivers is regulated by evaporation and recharge by rainwater as well as tidal flow downstream.
  • The estuarine channels in the Indian Sundarbans at present are mostly fed by tidal flow and have lost their freshwater connectivity.
  • Five rivers namely the Saptamukhi, Thakuran, Matla, Gosaba, and Harinbhanga in central section of Indian Sundarban are also tidally fed and lost their upstream freshwater connectivity.
  • Hyper-saline zone in the central part of the Sundarbans, which includes areas such as Raidighi and Patharpratima, have lost connectivity with the upstream freshwater flow.
• Both the glacial melting and sea level rise due to climate induced changes affect the salinity level.
• The rise in sea level, triggered by climate change, is one of the reasons for the increase in salinity of waters of rivers and channels.
• Anthropogenic factors like reduced discharge from barrages, runoff from adjacent lands, and water abstraction for irrigation etc.

About Ganges River Dolphin

• Ganges River Dolphin is one of the four freshwater dolphins of the world.
• The mammal is listed in the schedule I of the Indian Wildlife (Protection) Act, 1972, and categorized as “endangered” by the World Conservation Union and enjoys high level of legal protection, nationally and internationally.
• The Ganges River Dolphin, or susu, inhabits Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu river systems of Nepal, India, and Bangladesh.
• Ganges River Dolphin was declared India’s National Aquatic Animal in 2009.
• This cetacean is blind because it lacks crystalline. It moves by echolocation, that is, by waves emitted by the dolphin that bounce off objects and help it create a mental map of its direction and movement.

Other Freshwater Dolphin:

• Amazon river dolphin – Pink river dolphin or Amazon river dolphin. This dolphin is the largest freshwater dolphin
• Bolivian river dolphin – The Araguaian river dolphin, scientifically known as Inia geoffrensis geoffrensis, is a subspecies of the Amazon river dolphin
• La Plata Dolphin – This dolphin, commonly called Franciscana in Argentina and Uruguay, lives in the Río de la Plata in the South East of South America