Washington, July 30 : Scientists have determined that acidification of the sea is the biggest threat to marine animal life, hampering their reproduction.
By absorbing carbon dioxide from the atmosphere, and from the human use of fossil fuels, the world's seas function as a giant buffer for the Earth's life support system.
The chemical balance of the sea has long been regarded as immovable.
Today, researchers know that the pH of the sea's surface water has gone down by 0.1, or 25 percent, just since the beginning of industrialisation just over a century ago.
Jon Havenhand and Michael Thorndyke, researchers at the University of Gothenburg in Sweden, along with colleagues in Australia, have studied how this acidification process affects marine animal life.
As part of the study, which is one of the world's first on this subject, they have allowed sea urchins of the species Heliocidaris erythrogramma to fertilise themselves in water where the pH has been lowered from its normal 8.1 to a pH value of 7.7.
This means an environment three times as acidic, and corresponds to the change expected by the year 2100.
The results are quite alarming.
Like most invertebrates, the sea urchin multiplies by releasing its eggs to be fertilised in the open water. However, in a more acidic marine environment, the sea urchin's ability to multiply goes down by 25 percent, as its sperm swim more slowly and move less effectively.
If fertilisation is successful, their larval development is disturbed to the extent where only 75 percent of the eggs develop into healthy larvae.
According to Havenhand, "A 25 percent drop in fertility is the equivalent of a 25 percent drop in the reproductive population."
"It remains to be seen whether other species exhibit the same effect, but, translated to commercially and ecologically important species such as lobsters, crabs, mussels and fish, acidification would have far reaching consequences," he added.