SALLY SARA: Antarctic scientists have found that ocean acidification is eating away the shells of a creature known as the sea butterfly. The butterflies are actually tiny snails and they’re an important source of food for other creatures including fish and whales.
But increasing amounts of carbon dioxide in the ocean is making it more acidic, and that’s dissolving the shells of the sea butterflies.
Felicity Ogilvie reports from Hobart.
FELICITY OGILVIE: Floating through the oceans of Antarctica is a delicate creature that scientists call the sea butterfly.
DONNA ROBERTS: Well, they’re called sea butterflies because they’re actually a snail, they’re a sea snail. They’re a lot like a garden snail but they’re little slimy foot has evolved into the ocean into a pair of wings so that they can live in the aquatic environment, and they’re absolutely beautiful, so I actually think they should have been nicknamed sea angels instead of sea butterflies.
FELICITY OGILVIE: Dr Donna Roberts from the Antarctic Climate Ecosystems Research Centre in Hobart is an expert in the sea butterflies. She says the tiny creatures are called butterflies because they use their slimy wings to move around the ocean. But the creatures’ shells are being dissolved by ocean acidification.
DONNA ROBERTS: It’s basically like carbonating the ocean, especially in the polar regions, and it’s becoming a more acidic environment as we put more and more CO2 into the ocean, and unfortunately for the tetrapod, or sea butterfly, they’re the most at risk of detrimental effects of ocean acidification.
FELICITY OGILVIE: The rapid decline of the creatures’ shells has been outlined in a paper published in Nature Geoscience. The US-based scientist Dr Nina Bednar�ek is one of the main authors. She doesn’t know if the sea butterflies can survive without a shell.
NINA BEDNAR�EK: The shell is actually getting more fragmented, it’s losing the shape and so on, until it finally dissolves. So if they can survive without the shell or not, we actually at the moment we don’t know, but this animal would be much more affected by predators.
FELICITY OGILVIE: Dr Donna Roberts says that the sea butterflies are an important part of the Antarctic food chain.
DONNA ROBERTS: The unfortunate thing about sea butterflies is that they’re the potato chips of the sea, so everything eats them. They are food for commercial fish, for whales, for penguins, for seals, for seabirds, so if you like a good seafood meal, you should care about the Southern Ocean butterfly.
Actually, research in the Arctic has shown that Pacific Salmon actually eat – 90 per cent of their diet is the butterfly, so it’s a really important food staple for the Southern Ocean ecosystem, and we’re really worried about what this research is showing.
FELICITY OGILVIE: You specialise in studying these sea snails that are the butterflies of the sea. What’s the latest in you research?
DONNA ROBERTS: Our research has actually shown that their shells are actually being eaten away, increasingly, more every year.
FELICITY OGILVIE: And as you see the shells being eaten away, do you see any flow on effect to the other animals in the ocean?
DONNA ROBERTS: Well, anecdotally, every time I head out to the Southern Ocean to try to net some Southern Ocean butterflies, I actually see more and more jellyfish, so it does seem to me that there’s a decline in the butterfly and a huge increase in gelatinous organisms in the ocean.
So if we’re not careful, we might be looking at a jellyfish ocean in the future.
FELICITY OGILVIE: Dr Roberts heads to Antarctica every summer to trap and monitor the sea butterflies – and every year she’s finding less of the creatures.
SALLY SARA: Felicity Ogilvie.
Felicity Ogilvie, ABC News, 26 November 2012. Text and audio.