Environment

Are fish losing their sense of smell due to more-acidic oceans?

Are fish losing their sense of...
Although European sea bass were used in the study, the scientists state that the findings are applicable to other types of fish
Although European sea bass were used in the study, the scientists state that the findings are applicable to other types of fish
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Although European sea bass were used in the study, the scientists state that the findings are applicable to other types of fish
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Although European sea bass were used in the study, the scientists state that the findings are applicable to other types of fish

A couple of years ago we heard about a study conducted at Britain's University of Exeter, which indicated that increasingly acidic oceans were harming fishes' sense of smell. New research now reinforces that finding, and it could mean that trouble is in store for the marine ecosystem.

Sea water becomes more acidic as it absorbs carbon dioxide (CO2) from the atmosphere. Therefore, as atmospheric CO2 levels rise, so does the acidification of the earth's oceans – they're already an estimated 43 percent more acidic than they were at the time of the Industrial Revolution, and by the end of this century are predicted to be 2.5 times more acidic than they are now.

Unfortunately, it appears that such elevated acidity compromises fishes' ability to detect odors. This in turn makes it harder for them to find food, evade predators, recognize one another, and locate suitable spawning grounds.

"First we compared the behaviour of juvenile sea bass at CO2 levels typical of today's ocean conditions, and those predicted for the end of the century," says lead scientist Dr. Cosima Porteus, describing Exeter's latest research. "Sea bass in acidic waters swam less and were less likely to respond when they encountered the smell of a predator."

Additionally, the scientists recorded the electrical activity of the animals' nervous systems, as their noses were subjected to sea water with varying levels of absorbed CO2.

"The sense of smell of sea bass was reduced by up to half in sea water that was acidified with a level of CO2 predicted for the end of the century," says Porteus. "Their ability to detect and respond to some odors associated with food and threatening situations was more strongly affected than for other odors. We think this is explained by acidified water affecting how odorant molecules bind to olfactory receptors in the fish's nose, reducing how well they can distinguish these important stimuli."

Adding to the problem is the fact that when exposed to water with increased CO2 and acidity, the fish experienced a reduction in the expression of smell-sensing/processing genes in their nose and brain. In other words, instead of compensating for the nose's decreased ability to detect odors by increasing the expression of these genes, the fishes' bodies were just making things worse.

A paper on the research was recently published in the journal Nature Climate Change.

Source: University of Exeter

4 comments
watersworm
Just remind us of "mean" Ocean PH ?
Rumata
The study is totally wrong, because of many reasons. 1) they didn't prove by measurements, that oceans became more acidic during the last century. So it is not clear, how they could "predict" it. 2) In fact, the increase of CO2 level in the oceans is neglible, and the chemistry of the oceans is definitely basic (the contrary of acidic), because of their salt content. CO2 can form only a very weak acid, so it can only make sweet water (like rainwater) acidic. So there is no "acidification" in the oceans, except at some very special areas, where vulcanic activities bring up agressive acidic gases. 3) The oceans already contains a huge amount of CO2, 50 times more than the atmosphere. Even if we would burn all known fossile fuels on the Earth, it could only increase the CO2 level of the oceans with appr. 10%. And even that would have neglible effect on the ocean life.
Gregg Eshelman
Ocean Ph is not at all acidic. Ph must be above 7 to be called acidic. It's a bit below 7. 7 is neutral.
ljaques
Oh, well if U Exeter folks said it, and it was published in a global warming mag, then you know it's true and WEREALLGONNADIE,AGAIN!