Ocean acidification puzzles fish and shellfish

Researchers who participated in a recent international meeting state that the more acidic oceans become, the more hyperactive and puzzled some fish and shellfish turn, approaching their predators instead of trying to escape from them.

And the French scientist Jean-Pierre Gattuso, of Villefranche Oceanography Laboratory, warned that “ocean conditions are changing 100 times faster than at any time in the past.”

Gattuso is one of nearly 600 scientists from around the world, who presented their research results at the third symposium ‘The Ocean in a High-CO2 World: Ocean Acidification,’ held in the city of Monterey, United States, reported IPS.

About 10 years ago, science discovered that burning fossil fuels — coal, oil and gas –caused ocean waters to be 30 per cent more acidic than at the beginning of the Industrial Revolution.

It is estimated that oceans absorb one third of the carbon dioxide (CO2) resulting from human activities. When this gas is dissolved in sea water, carbonic acid is formed and the water becomes more acidic.

This phenomenon, known as ocean acidification, decreases carbonate availability and makes it more difficult for the hard parts of many marine organisms that need calcium carbonate to be formed.

Acidity also affects coral reefs, certain shellfish and other species with hard parts such as shells or skeletons, Gattuso stated.

For example, he said pteropods, tiny swimming molluscs, are becoming “naked” without their protective shells due to increased acidity.

In turn, this species is eaten by many others and is a key element in the Antarctic Ocean, he added.

Meanwhile, Chilean scientists who participated in the symposium revealed that Chilean locos or sea snails (Concholepas concholepas) registered changes in behavior due to the water acidity.

Patricio Manríquez, of the Institute of Marine and Limnological Sciences of the Faculty of Sciences of Universidad Austral de Chile, said this resource “is a type of food that has great social and economic importance” in the country and its main predator is Acanthocyclus hassleri, an intertidal carnivore crab.

The Chilean locos have the ability to smell crabs and escape so as not to be eaten but in situations where water has a high degree of acidity, Chilean locos feel puzzled, moving erratically and often heading towards predators, Manríquez added.

He added: “There have been no changes in the growth rate or in the size of the snails.”

Anyway, at least 10 additional studies being carried out on the effect of acidity on larvae and shells, among other issues.

Moreover, Australian researchers explained that ocean acidity affects the behaviour of some tropical reef fish.

Philip Munday, a scientist at the School of Marine and Tropical Biology at James Cook University, said that while noting that fish support the acidification of internal tissues, they concluded that “there are sublethal effects.”

The ocean acidity extent results in increased “level of activity, performance and audacity. They become more active and take more risky behaviour,” the Australian researcher argued.

However, the researchers gathered in Monterey agreed that overfishing, and especially in the case of trawling is the main immediate threat to marine ecosystems.

They also agreed that there is sufficient evidence to recommend that governments take immediate action to reduce CO2 emissions and protect oceans for the future.

Analia Murias, FiS, 5 October 2012. Article.


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