Washington, April 2 : Scientists have suggested that coral reefs could be dying out because of changes to the microbes that live in them just as much as from the direct rise in temperature caused by global warming.
Corals in coral reefs, which are made up of animals called polyps that secrete hard external skeletons of calcium carbonate, are living perilously close to their upper temperature limits.
This makes them very vulnerable to even small temperature rises of 1-2oC above the normal summer maximum.
According to Dr John Bythell, a biologist from Newcastle University, "Many of the deaths we see in the coral reefs, which occur following coral bleaching events, when huge areas of reef die off like in 1998 when 17% of the world's reefs were killed, can be put down to changes in the microbes which live in and around the reefs."
"These microbes can be thought of as being similar to the bacteria that normally live in our guts and help us digest our food," he added.
Changes in sea temperature caused by climate change and global warming affect corals, but they also affect the types of bacteria and other microflora that live with them. When the water warms up, some disease-causing bacteria are more successful and can attack the corals.
The corals themselves suffer from heat, which reduces their defences.
Also, some of the friendly bacteria that normally live in the corals' guts become weakened, allowing other harmful bacteria to multiply and cause diseases or other problems.
"We need a better understanding of the processes and mechanisms that impact on corals and the reefs when sea temperatures rise to confirm the ultimate causes of their decline," said Dr Bythell.
According to Dr Bythell, scientists' attempts to identify the underlying problems would be improved by combining molecular microbial techniques with coral cell and molecular approaches.