Changing weather: Sea surface is heating up

Visakhapatnam: The rising sea surface temperatures (SST) in the Bay of Bengal have been posing a threat to the existence of certain fish and other marine species. The variations in SST have been due to rampant pollution in sea and also due to human activities on the coast.

Fishermen catch fish varieties ranging between 30 to 40 species in the Bay of Bengal and they are being affected by the variations in sea temperatures.

Scientists observed that rise in temperatures between 1977-2005 was more than that between 1961-1976. They also found that the average sea surface temperature has risen by 0.5° Celsius since 1957. Sea surface temperature was between 27.7°Celsius and 28°Celsius during 1961-76 and it rose up to 28.7 ° Celsius to 29°Celsius during 1977-2005.

Predictions of the Inter-governmental Panel on Climate Change indicate that average SST of the Indian Ocean is likely to increase by 2° Celsius to 3.5°Celsius by the end of the Century  and that would significantly affecting El Nino (SST that cause climactic changes) and monsoon systems.

“Increasing vehicular pollution has triggered changes in phytoplankton populations in the Bay of Bengal, upsetting the delicate composition of surface waters and consequently, causing small pelagic fish to migrate from hot zones to cooler ones. Now, sardine fish, once available in plenty off the Tamil Nadu coast are found off the Vizag coast,” said Dr M.M. Prasad, scientist in-charge of the Central Institute of Fisheries Technology. He said studies are being focused on varieties of fish affected by the process.

The surface ocean also absorbs carbon dioxide released by vehicles and industries. This changes the surface ocean carbonate chemistry by lowering the pH value through acidification which would also affects the existence and migration of living beings, he added.

Studies indicate that the Ganga, Brahmaputra, Mahanadi, Godavari, Krishna and Cauvery  Rivers discharge around 665 million tonnes of sediment per annum into the Bay of Bengal. This is resulting  in a reduction of the depth of the sea. It also has been causing a massive eutrophication (ecosystem being enriched by chemical nutrients) process, a leading cause of impairment of freshwater and coastal marine ecosystems.