The pteropod, which inhabits the top 200 metres of oceanic waters, is a key source of food for other marine animals. (Nina Bednarsek )

As the oceans become more acidic due to high carbon dioxide levels, marine life is being visibly affected, according to a study of Antarctic marine snails.

Called pteropods, the snails are a key link in the ocean’s food chain, a vital source of nutrient for fish and birds  A team of international researchers has discovered the high acidity of the waters is corroding the pteropods’ shells.

The study, published in Nature Geoscience, was a combined project involving scientists from the British Antarctic Survey, Royal Netherlands Institute for Sea Research, the U.S. National Oceanic and Atmospheric Administration (NOAA) and other institutions.

The burning of fossil fuels has spewed additional carbon dioxide into the atmosphere which, in turn, is absorbed by the oceans. scientists say. This changes the chemistry of the waters, which become more acidic over time.

"The corrosive properties of the water caused shells of live animals to be severely dissolved, and this demonstrates how vulnerable pteropods are," said lead author Nina Bednaršek from the NOAA.

The study marks the first time an acidification analysis was conducted on live specimens in their natural environments. 

The scientists were concerned, in particular, with the effects of upwelling on the snails. Upwelling occurs when deep sea water is forced to the surface by extreme winds, and climate models have indicated that upwelling will become more common in the future.

The combination of upwelling and the more acidic nature of the surface water have served to make the environment more corrosive. Pteropods live at the surface of the oceans to a depth of 200 metres.

According to the NOAA, the acidity of surface ocean waters has increased by 30 per cent since the Industrial Revolution. At the current rate that CO2 levels are rising, the waters could be almost 150 per cent more acidic by the end of the century, scientists estimate.

Dr. Geraint Tarling of the British Antarctic Survey and the study’s co-author said the research team will now undertake a "more comprehensive" study looking at the effects of ocean acidification on a wider range of organisms.