Guardian: Biologists warn that hundreds of species could die or weaken as growing levels of CO2 make oceans more acidic and disrupt shell formation Sea creatures are set to shrink as the world’s oceans become more acidic. That is the startling warning given by an international group of biologists who have charted the likely impact of rising carbon dioxide levels on marine life. The group reveals that not only are hundreds of marine species likely to be wiped out as more and more carbon dioxide is dissolved in the Earth’s oceans but also that creatures that do survive – in particular those with shells, such as clams, oysters and snails – will be left puny and shrunken as a result. “We have already seen this effect in commercial oyster beds in the US, where marine farmers have had to stop growing young oysters in sea water because their shells could no longer form properly in our increasingly acidic seas. Instead they have to grow them in tanks where water acidity can be controlled,” said marine biologist Professor Jason Hall-Spencer, of Plymouth University. “And as the oceans get even more acidic, the problem of species shrinkage – known as the Lilliput effect – will become more and more common. It is a clear warning of the extreme dangers we are facing as carbon emissions continue to rise around the planet.” Scientists estimate that the oceans absorb around a million tonnes of carbon dioxide every hour. As a result our seas have become 30% more acidic than they were a century ago. This increased acidity plays havoc with levels of calcium carbonate, which forms the shells and skeletons of many sea creatures, and also disrupts reproductive activity. These threats have led to the phenomenon of ocean acidification being dubbed global warming’s “equally evil twin”.