Carbon emissions threaten fish populations

Jul 07, 2010

Humanity's rising CO2 emissions could have a significant impact on the world's fish populations according to groundbreaking new research carried out in Australia.

Baby fish may become easy meat for predators as the world's oceans become more acidic due to CO2 fallout from human activity, an international team of researchers has discovered.

In a series of experiments reported in the latest issue of the (PNAS), the team found that as carbon levels rise and ocean water acidifies, the behaviour of baby fish changes dramatically - in ways that decrease their chances of survival by 50 to 80 per cent.

"As CO2 increases in the atmosphere and dissolves into the oceans, the water becomes slightly more acidic. Eventually this reaches a point where it significantly changes the sense of smell and behaviour of larval fish," says team leader Professor Philip Munday of the Australian Research Council's Centre of Excellence for Coral Reef Studies (CoECRS) at James Cook University.

"Instead of avoiding predators, they become attracted to them. They appear to lose their natural caution and start taking big risks, such as swimming out in the open - with lethal consequences."

Dr Mark Meekan from the Australian Institute of Marine Science, a co-author on the paper, says the change in fish behaviour could have serious implications for the sustainability of because fewer baby fish will survive to replenish adult populations.

"Every time we start a car or turn on the light part of the resulting CO2 is absorbed by the oceans, turning them slightly more acidic. Ocean pH has already declined by 0.1 unit and could fall a further 03.-0.4 of a unit if we continue to emit CO2 at our present increasing rate.

"We already know this will have an adverse effect on corals, shellfish, plankton and other organisms with calcified skeletons. Now we are starting to find it could affect other marine life, such as fish."

Earlier research by Professor Munday and colleagues found that baby 'Nemo' clownfish were unable to find their way back to their home reef under more acidic conditions. The latest experiments cover a wider range of fish species and show that acidified sea water produces dangerous changes in fish behaviour.

"If humanity keeps on burning coal and oil at current rates, atmospheric CO2 levels will be 750-1000 parts per million by the end of the century. This will acidify the seas much faster than has happened at any stage in the last 650,000 years.

"In our experiments we created the kind of sea water we will have in the latter part of this century if we do nothing to reduce emissions. We exposed baby fish to it, in an aquarium and then returned some to the sea to see how they behaved.

"When we released them on the reef, we found that they swam further away from shelter and their mortality rates were five to eight times higher than those of normal baby fish," Professor Munday says.

He adds it should be clearly understood that this impact is likely to happen independent of global warming, and is a direct consequence of human carbon emissions.

The research team concludes "Our results demonstrate that additional CO2 absorbed into the ocean will reduce recruitment success and have far-reaching consequences for the sustainability of fish populations."

Professor Munday adds "In its 2008 report on the state of the world's fisheries the UN Food and Agriculture Organization said "the maximum wild capture fisheries potential from the world's oceans has probably been reached". If you add the impact of acidification and other climate change impacts to this, it means there are grounds for serious concern about the future state of world fish stocks and the amount of food we will be able to obtain from the sea."

Explore further: Tracking giant kelp from space

More information: The article "Replenishment of fish populations is threatened by ocean acidification" by Philip L. Munday, Danielle L. Dixson, Mark I. McCormick, Mark Meekan, Maud C.O. Ferrari and Douglas P. Chivers appears in the latest issue of PNAS.

Provided by ARC Centre of Excellence in Coral Reef Studies

3.7 /5 (3 votes)
add to favorites email to friend print save as pdf

Related Stories

Fish guts explain marine carbon cycle mystery

Jan 15, 2009

Research published today reveals the major influence of fish on maintaining the delicate pH balance of our oceans, vital for the health of coral reefs and other marine life.

Reef 'at risk in climate change'

Apr 06, 2007

Australian scientists who contributed to the latest global greenhouse study say the Great Barrier Reef is one of the nation's great assets most at risk under climate change.

'Evil twin' threatens world oceans, scientists warn

Mar 29, 2010

(PhysOrg.com) -- The rise in human emissions of carbon dioxide is driving fundamental and dangerous changes in the chemistry and ecosystems of the world’s oceans, international marine scientists warned today.

Turf wars: Sand and corals don't mix

Oct 08, 2008

When reef fish get a mouthful of sand, coral reefs can drown. That's the latest startling evidence to emerge from research into the likely fate of reefs under climate change and rising sea levels, at the ARC Centre of Excellence ...

Ocean acidification threatens cold-water coral ecosystems

Apr 03, 2006

Corals don't only occur in warm, sun-drenched, tropical seas; some species are found at depths of three miles or more in cold, dark waters throughout the world's oceans. Some cold-water coral reefs are home to more than 1,300 ...

Recommended for you

Tracking giant kelp from space

22 minutes ago

Citizen scientists worldwide are invited to take part in marine ecology research, and they won't have to get their feet wet to do it. The Floating Forests project, an initiative spearheaded by scientists ...

Heavy metals and hydroelectricity

1 hour ago

Hydraulic engineering is increasingly relied on for hydroelectricity generation. However, redirecting stream flow can yield unintended consequences. In the August 2014 issue of GSA Today, Donald Rodbell of ...

What's wiping out the Caribbean corals?

2 hours ago

Here's what we know about white-band disease: It has already killed up to 95 percent of the Caribbean's reef-building elkhorn and staghorn corals, and it's caused by an infectious bacteria that seems to be ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

jscroft
not rated yet Jul 07, 2010
Good G-d what utter rubbish. The majority of atmospheric CO2 is outgassed FROM the ocean as a consequence--not a cause, darn it--of global warming.

Will the Kool-Aid EVER run out???