Panaji: Coral reefs which are home to over 25 per cent of marine life, are facing a double blow across the globe in the form of thermal and chemical impact, a senior scientist said.
"Thermal impact on the earth is seen in terms of global warming. Earth has warmed by about 0.34 degree Celsius since the mid 1970s and the eight warmest years on record have occurred since 2001," senior scientist with Goa-based National Institute of Oceanography (NIO) Dr Mahua Saha, told representatives of SAARC nations.
Saha was deliberating on the topic impact of climate change on coral reefs during ongoing five-day workshop of SAARC nations organised by NIO for SAARC Coastal Zone Management Centre at Port Blair in Andaman and Nicobar Islands, which concludes on December 19.
"As per IPCC (Intergovernmental Panel on Climate Change), by the end of this century, the best estimate of temperature increase is almost two degree Celsius. This trend makes the land and ocean warmer and alters long term weather patterns," she said.
Policy makers and scientists from four SAARC nations - India, Bangladesh, the Maldives and Sri Lanka - are taking part in the event.
The discussions during the workshop will decide the roadmap for the SAARC nations on the issue.
Dr Saha said since industrial revolution, human activities have increased the concentration of green house gases leading to gradually increase the temperature of land and the ocean.
"Prolonged warmer water temperature caused by climate change impacts coral growth adversely as they can tolerate only a narrow range of water temperature between 18 to 29 degrees Celsius," Saha said, presenting the scenario to the participating nations.
The indirect effect of elevated temperature causes sea level rise due to melting of ice and also thermal expansion of water.
The rising sea levels cause threat to most of the corals by making them inaccessible to receive sunlight which is required for their survival, she said.
Dr Saha said that another major concern for the coral reef is huge amount of carbon dioxide released in the atmosphere, half of which is absorbed by oceans, causing bio-chemical impact.
"Increased amount of carbon dioxide dissolves more into the ocean causes decrease of pH (parameter used to calculate acidity) which leads to acidify the ocean waters," she said, adding, increasing amount of acid reacting with coral structure make it weaken and less susceptible to the environment that leads to coral destruction.
According to Royal Society (2008 survey), the ocean change of pH from 1751 to 2008 is from 8.179 to 8.069 which shows that the acidity of ocean is increasing, the scientist said.
The senior scientist also expressed concern that not much work has been done to study effect of ocean acidification on corals and to what extent ocean is acidifying over time and what is the threat level of acidity to corals to lose its structure.