Heat hurts shellfish relationships

OYSTERS, lobsters, mussels, sea urchins and abalone could be wiped off the menu by global warming, an Australian scientist warned yesterday.

Jane Williamson, a Macquarie University marine ecologist, made the prediction after discovering that climate change is likely to take a dramatic toll on the ability of sperm from many marine creatures to swim to and fertilise eggs shed in the water.

Even if sperm can find and fertilise the eggs, the probability of their surviving long enough to grow into larvae is likely to plunge.

If the decline in reproduction observed in the laboratory is repeated in nature, Dr Williamson said, “it could be enough to tip an ecosystem shift. Whole communities of marine animals could disappear.”

As global temperatures rise the oceans are absorbing more carbon dioxide from the atmosphere, triggering chemical reactions increasing water acidity.

Scientists have found evidence that increasing ocean acidity is eating into the shells of many marine animals, making them thinner and more fragile. But the new fertility research shows that rising acidity will pose a second serious threat to sea life.

In the laboratory, Dr Williamson’s team exposed several species of sea urchins to water with an acidity of 7.7 – the same level that climate-change scientists have predicted the world’s oceans will reach by 2100.

Like most marine invertebrates – including oysters, abalone, mussels and lobsters – sea urchins release sperm and eggs into the water. The Sydney scientists, whose research has been published in Current Biology, found that when exposed to acidity levels of 7.7, three times today’s global sea average, sea urchin sperm swam much more slowly.

The sperm also lost the ability to swim in the spiralling “corkscrew” pattern used to intercept eggs. “They slow down a lot and the corkscrew goes haywire,” Dr Williamson said. “It means the sperm aren’t meeting the eggs.”

Overall, fertilisation fell by 25 per cent, and in almost 26 per cent of cases where the eggs were fertilised they did not survive long enough to develop into larvae.

Dr Williamson and her collaborators, Professor Jon Havenhand and Professor Michael Thorndyke, from Gothenburg University, are testing mussels, sea stars and oysters and finding similar results.

Scientists have warned that the oceans can no longer cope with the uptake of carbon dioxide, and rising acidity “is an urgent scientific and policy challenge”.

Dr Will Howard, from Australia’s Antarctic Climate and Ecosystems Co-operative Research Centre, and Dr Bronte Tilbrook,from the CSIRO, released a statement on behalf of scientists at a Hobart conference in June. “The current trajectory of carbon emissions will cause a change in ocean acidity during this century that is greater in extent than anything likely to have occurred for millions of years,” it said.

Richard Macey, The Sydney Morning Herald, 15 August 2008. Article.

  • Reset


OA-ICC Highlights

%d bloggers like this: