Acidic oceans cause fish to lose their sense of smell

July 23, 2018, University of Exeter

When carbon dioxide is absorbed by seawater carbonic acid is formed, making the water more acidic. Since the Industrial Revolution, oceanic CO2 has risen by 43% and is predicted to be two and a half times current levels by the end of this century.

Fish use their sense of smell (olfaction) to find food, safe habitats, avoid predators, recognize each other and find suitable spawning grounds. A reduction in their ability to smell therefore can compromise these essential functions for their survival.

The new study provides evidence that economically important species will be affected by elevated CO2, leaving fish vulnerable because it affects their ability to detect odours.

University of Exeter researcher Dr. Cosima Porteus, who led the study, said: "Our study is the first to examine the impact of rising carbon dioxidein the ocean on the olfactory system of fish. 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. Sea bass in acidic waters swam less and were less likely to respond when they encountered the smell of a predator. These fish were also more likely to "freeze" indicating anxiety."

Experts at the University of Exeter, in collaboration with scientists from the Centre of Marine Sciences (CCMar, Faro, Portugal) and the Centre for Environment, Fisheries and Aquaculture Science (Cefas), also tested the ability of the sea bass' nose to detect different smells. They did this by recording the activity in the nervous system while their nose was exposed to water with different levels of CO2 and acidity.

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Increasing ocean acidity could impact fish spawning

By Matt McGrath

Environment correspondent

27 July 2016

A new study suggests that the increasing acidification of the oceans is likely to interfere with the ability of fish to reproduce.

Researchers found that elevated levels of CO2, which make the waters more acidic, saw significantly lower levels of spawning.

However, other mating behaviours of the same species were unaffected by the souring of the oceans.

The scientists say the changes are "subtle but ecologically important".

The study examined the complicated mating behaviours of ocellated wrasse, a common Mediterranean fish.

There are three different types of male who compete to father the offspring of this species.

Sneaky males

Dominant males build nests and provide defence, while satellite males aid the dominants in return for a share of the eggs. "Sneaker" males hover around the nests and try and take advantage when the dominants are distracted.

The researchers filmed and studied the complex interactions of these creatures in areas near underwater volcanic vents which seep CO2 into the water.

The higher levels of CO2 make the sea much more acidic in this area off the coast of southern Italy, equivalent to what is expected more widely around the world by the end of this century.

The scientists found that many mating behaviours were unaffected but that dominant male spawning with females was reduced by almost two thirds in areas of high CO2.

The researchers argue that the increased CO2 may be impacting the abilities of the dominant males to make rapid decisions.

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Increasingly acidic oceans threaten world's mussel populations

Mussel shells could become more brittle as climate change causes acidity of world’s oceans to rise, scientists have warned

Press Association

Wednesday 24 December 2014 06.00 GMT

The world’s mussel population could be under threat as climate change causes the oceans to become more acidic, scientists have warned.

Mussel shells become more brittle when they are formed in more acidic water, Glasgow University has reported in the Royal Society journal Interface.

Carbon dioxide in the atmosphere causes the oceans to become more acidic and reduces the concentration of the minerals mussels need to generate their shells, according to scientists.

However, they also found that mussels may have an in-built biological defence mechanism which boosts shell development when water temperatures rise by 2C.

Dr Fitzer said: “What we’ve found in the lab is that increased levels of acidification in their habitats have a negative impact on mussels’ ability to create their shells.

“We worked with colleagues in our School of Engineering to examine the toughness of the shells of the mussels in the more acidic water against those in control conditions.

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Researchers discover ocean acidity is dissolving shells of tiny snails off the US West Coast

A NOAA-led research team has found the first evidence that acidity of continental shelf waters off the West Coast is dissolving the shells of tiny free-swimming marine snails, called pteropods, which provide food for pink salmon, mackerel and herring, according to a new paper published in Proceedings of the Royal Society B.

Researchers estimate that the percentage of pteropods in this region with dissolving shells due to ocean acidification has doubled in the nearshore habitat since the pre-industrial era and is on track to triple by 2050 when coastal waters become 70 percent more corrosive than in the pre-industrial era due to human-caused ocean acidification.

The new research documents the movement of corrosive waters onto the continental shelf from April to September during the upwelling season, when winds bring water rich in carbon dioxide up from depths of about 400-600 feet to the surface and onto the continental shelf.

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