Fish scientists proved years ago that the tiniest traces of copper in water can affect a salmon’s sense of smell.

Now, research shows that increasing levels of acidity in the oceans do the same thing.

The damage is caused by the ocean’s absorption of carbon dioxide, which is generated primarily by the burning of fossil fuels, like oil and coal. The CO2 combines with seawater to produce carbonic acid, which makes the water more acidic.

A sense of smell is critical to fish. They use it to find food, elude predators, find  spawning areas, even to recognize one another. Losing it could threaten their very survival, and mean big trouble for the fishing industry, tourism and, most importantly, global nutrition,

  In the environment that has some serious implications. If there are predators around and the fish are not able to response to these danger signals in the water, I guess they would be the next snack for these larger predators in the water.

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Jason Sandahl at Oregon State University was one of the first to show how contaminants can disrupt the chemical balance of sea creatures. His studies showed that copper levels at just two parts per billion impaired small salmon’s sense of smell.

Last month scientists at England’s University of Exeter compared the behavior of juvenile sea bass at carbon dioxide levels typical of today’s ocean conditions with those predicted for the end of the century.

They chose to study sea bass because they are economically important both for both commercial and  sport fishing.

The results showed the sense of smell in the fish was reduced by half.  They also found that sea bass exposed to the more acidic conditions swam less and were less likely to react when encountering the smell of a predator.

The scientists also measured the ability of the fish to detect certain odors in different levels of acidity by recording their nervous system activity. The longer the fish were in high CO2 levels, the worse they fared.

The fish also made fewer smell receptors in their nose and brains.

The scientists concluded that future levels of carbon dioxide can affect fish population numbers and entire ecosystems.

While their study was on sea bass, the researchers believe all commercially important species are likely to be affected in a similar way, and possibly crabs and lobsters as well.

The study was published last month in the journal Nature Climate Change.

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