Sea bass exposed to high levels of carbon dioxide lost around half their sense of smell ( Getty )
Fish are losing their sense of smell as rising carbon emissions turn the water they live in to acid.
A new study has revealed that as levels of carbonic acid in seawater rise, sea bass lose up to half their smelling capacity.
Surges in atmospheric carbon dioxide increase ocean acidity as the gas dissolves in water – a phenomenon already known to dissolve the hard outer coatings of shellfish.
The findings are significant as these fish rely on smell to do everything from finding food and potential mates to detecting predators in their vicinity.
“Our study is the first to examine the impact of rising carbon dioxide in the ocean on the olfactory [smell] system of fish,” said University of Exeter researcher Dr Cosima Porteus, who led the research.
The scientists compared the behaviour of young sea bass at current carbon dioxide levels to the levels expected at the end of the century, when oceans are predicted to contain up to two and a half times the levels of the gas seen today.
They noticed big changes in the behaviour of the fish inhabiting the most acidic water. Not only did the bass swim less, they appeared not to notice the presence of predators.
Previous research has indicated that besides directly affecting fish noses, carbon dioxide harms fish nervous systems and disrupts the processing of information in their brains.
“It is not yet known how rapidly fish will be able to overcome these problems as carbon dioxide rises in the future,” said Professor Rod Wilson from the University of Exeter, who was involved in the study.
“However, having to cope with two different problems caused by carbon dioxide, rather than just one, may reduce their ability to adapt or how long this will take.”
Other studies have suggested that as seawater becomes more acidic, it will erode the hearing ability of fish including the clownfish and make them unable to hear approaching predators.
“It is not yet known how rapidly fish will be able to overcome these problems as carbon dioxide rises in the future,” said Professor Rod Wilson from the University of Exeter, who was involved in the study.
“However, having to cope with two different problems caused by carbon dioxide, rather than just one, may reduce their ability to adapt or how long this will take.”
Other studies have suggested that as seawater becomes more acidic, it will erode the hearing ability of fish including the clownfish and make them unable to hear approaching predators.
Josh Gabbatiss, Independent, 23 July 2018. Article.
Note that the terminology used in this article is misleading. The definition of “acidic” in the Oxford English dictionary is “having the properties of an acid; having a pH of less than 7″. Despite the process of ocean acidification, the oceans are alkaline (pH higher than 7) and will not become acidic in the foreseeable future. Hence, “acid” or “acidic” should not be used when referring to seawater. Note that there are few exceptions, seawater can be acidic in the immediate vicinity of CO2 vents or in purposeful perturbation experiments