Marine abalone and sea urchins in Sydney Harbour will not develop normal skeletons if the ocean continues to warm and acidify as predicted, a study has found.

Such impaired development could have a dramatic effect on the survival of these economically and ecologically important sea creatures.

A group of Australian marine biologists reared abalone and sea urchins in present ocean conditions and compared them with young raised in warmer, more acidic environments that scientists predict will become reality for the world’s oceans within the next 100 years.

While abalone larvae raised in control conditions had a well-developed shell after 21 hours of life, most larvae reared in water with a pH of 7.6 – a 0.4 drop in pH level compared with today – were dead or severely abnormal after the same time frame. An increase in temperature of just two degrees had a negative effect on baby abalone development and only 20 per cent of young raised in water four degrees warmer than today survived.

The study found developing abalone had only a limited ability to cope with changes in temperature and acidity, and larvae could not recover and grow shells when they were placed in normal conditions.

”Near-future ocean conditions resulted in unshelled abalone larvae, a condition that prevents survival to the juvenile stage,” wrote the authors, whose study was published in Proceedings of the Royal Society B.

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Nicky Phillips, The Sydney Morning Herald, 7 March 2011. Full article.