Rising acidification of the ocean could reduce fertilisation of marine invertebrates and might eventually wipe out colonies of sea urchins, lobsters, mussels and oysters, according to a study.

The new study has found that rising acidity hindered marine sperm from swimming to and fertilising eggs in the ocean. Climate change and the subsequent acidification of the world’s oceans will significantly reduce the successful fertilisation of certain marine species by the year 2100, said the report by Australian and Swedish scientists.

“If you look at projected rates (of acidity) for the year 2100, we are finding a 25 per cent reduction in fertilisation,” lead-scientist Jane Williamson from Macquarie University said on Friday.

“We were completely surprised because people had been looking at the effect of acidification on calcified structures of marine animals, but there was no evidence to suggest it was affecting non-calcified structures, like a sperm or an egg,” she said.

The surface of the ocean absorbs up to 30 per cent of the world’s yearly emissions of carbon dioxide. Absorbed carbon dioxide forms a weak acid that is gradually increasing the acidity of the oceans. The study of sea urchins around southeast Australia found a link between increased ocean acidity and a reduction in speed and motility of sea urchin sperm.

The researchers measured sperm swimming speed, sperm motility, fertilisation success and larval developmental success in sea urchins in normal seawater with a pH 8.1 and also in water with a pH 7.7, which is projected to be the level of acidification by 2100.

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