Scientists say increasingly acidic ocean water is actually starting to dissolve tiny sea creatures.
The shells of sea butterflies, tiny snails about the size of a pinhead that live in the uppermost layer of the Southern Ocean near Antarctica are being corroded by sea water that contains higher levels of carbon dioxide than normal.
Human activity has increased atmospheric levels of CO2 exponentially in the last several hundred years. Much of that carbon dioxide ends up dissolved in the oceans, much like the way carbon dioxide is dissolved in water to make carbonated beverages.
This forms carbonic acid, which is relatively harmless to humans in small doses but wreaks havoc on the fragile calcium-based shells of marine life. It's also the reason why carbonated sodas are bad for your teeth.
Sea butterflies, also known as pteropods, stay near the surface of the ocean, because the water father down is naturally more acidic. But reserachers have detected pteropods with corroded shells as close as 200 meters from the ocean's surface, a much more shallow depth than previously recorded.
When the scientists measured the acidity of the surrounding water, they found that pH levels are decreasing closer to the surface, meaning the water is becoming more acidic.
"We know that the seawater becomes more corrosive to aragonite shells below a certain depth - called the 'saturation horizon' - which occurs at around 1000m depth," said Dr. Nina Bednaršek of the National Oceanic and Atmospheric Administration.
"However, at one of our sampling sites, we discovered that this point was reached at 200 meter depth, through a combination of natural upwelling and ocean acidification. Marine snails - pteropods - live in this top layer of the ocean. The corrosive properties of the water caused shells of live animals to be severely dissolved and this demonstrates how vulnerable pteropods are. Ocean acidification, resulting from the addition of human-induced carbon dioxide, contributed to this dissolution."
Pteropods are a vital part of the ecosystem and food chain, helping to feed small marine life and commercial fish like salmon, which could become more scarce as their prey die out.
Carbon dioxide levels in the oceans worldwide have increased 30 percent since the beginning of the Industrial Revolution, when humans began ejecting massive amounts of carbon from fossil fuels into the atmosphere.