Australasian Science: Australia's authority on science since 1938

Snails Lose their Spring

By Stephen Luntz

Sea snails exposed to high levels of carbon dioxide lose their capacity to avoid predators, with worrying implications for marine ecosystems.

Conch snails use their strong foot to jump, principally away from marbled cone shell predators. However, when exposed to water with the carbon dioxide levels anticipated at the end of the century, Dr Sue-Ann Watson of the Coral Centre of Excellence found that the snails either took longer to jump or failed to leap at all when exposed to attack. “Altered behaviours between predators and prey have the potential to disrupt ocean food webs,” Watson says.

The study, published in the Proceedings of the Royal Society B: Biological Sciences, followed up research showing that fish change their behaviour when exposed to high levels of carbon dioxide in the water. “We were keen to see if marine invertebrates were also affected,” says Watson. “The jumping snails are a good subject because they have this easily observed behaviour.”

For both fish and the snails the response has been attributed to the interference of carbon dioxide with the GABA-A neurotransmitter.

While the implications are dire for marine species, Watson’s co-author, Prof Goran Nilsson of the University of Oslo, has concluded that only water-breathing creatures should be affected. Terrestrial animals, and air-breathers such as dolphins and turtles, should not suffer from the higher carbon dioxide in the air.

Watson says that research to investigate the effects on invertebrate predators, including the cone shell, has begun but results are not available.

The key unknown remains the ability to adapt to high carbon dioxide conditions in the limited time available. Watson says that past high levels of carbon dioxide have been associated with mass extinctions, but the snail’s ancestors survived. However, these occurred with much slower increases than are anticipated this century.