The world's oceans have soaked up half of the carbon dioxide pumped into the air by human activities since the beginning of the industrial age, according to new two studies. The gas is acidifying the seas and may harm marine life, the authors warn. Atmospheric carbon dioxide has shot up from 280 parts per million (ppm) in 1800 to 380 ppm today. However, that figure would be greater than 435 ppm were it not for the oceans. The oceans are producing this tremendous service to humankind by reducing the amount of carbon dioxide in the atmosphere, which can lead to global warming. But it's changing the chemistry of the oceans and may have consequences for marine ecosystems. It has been discovered that the oceans have absorbed 48 per cent of all CO2 from fossil-fuel burning and cement manufacturing, which is dissolved in the top 10 percent of the world's seas. However, when carbon dioxide dissolves in seawater, it forms carbonic acid, which in turn can dissolve the shells and skeletons of marine life. For example, the snail species Clio pyramidata lose their ability to grow their shells, having being exposed to carbon dioxide at levels of 1000 ppm for just 48 hours. The animals' survival or reproductive success may also be affected, or they may have to move to waters with lower carbon dioxide concentrations. The dissolution of the calcium carbonate shells of animals and plankton also plays a key role in ocean chemistry and those effects are critical to understand how the oceans can absorb carbon dioxide from the atmosphere in the future. While it's clear that putting more carbon dioxide into the ocean would help global warming but there would be some biological cost associated with that and there is no guarantee as to if there would be a net benefit or not.