Carol Turley

Ocean Acidification – What it is and does it matter?

MedSeA MRUG Meeting, Barcelona 24th February 2011

What is Ocean Acidification?

When CO2

is added to water it becomes an acid…

…so the oceans have become 30% more acidic, lowering the pH of seawater

….by 2060 the oceans could become 120% more acidic

This is resulting in increased carbon dioxide (CO2

) in the atmosphere causing global warming

Mankind is burning fossil fuelOceans are vast and are taking up the CO2

What is Ocean Acidification: the chemistry….

Over the last 200 yrs the oceans have become 30% more acidic, lowering the pH and carbonate ions

….by 2060 the oceans could become 120% more acidic

Oceans are Acidifying Fast ……….

It is happening now, at a rate and to a level not experienced by marine organisms for ~ 20MY

Changes in pH over the last 25 million years

Turley et al. 2006

Aragonite Saturation State of Surface Waters (Orr et al 2005, Nature)

Aragonite is used by many organisms to make their shells and skeletons.

The extent of aragonite saturation controls the rate an organism such as a reef forming coral can build its skeletons or shells

good

Not good - corrosive

Note:

• Overall decline in aragonite saturation in the global ocean

• Polar and subpolar waters become undersaturated (corrosive)

Present and Future Global Aragonite Saturation States…

Polar Oceans are Vulnerability too….

Steinacher et al. 2008, Orr et al. 2009

If CO2 emissions continue to rise as today (Orr et al.):

- 10% of Arctic surface waters will be corrosive by 2018 - 50% by 2050 - 100% by the end of the century

Early vulnerabilities: upwellings, estuaries and tropical and cold water corals

Cao and Caldeira (2008)

Guinotte et al 2006

Feely et al. Science (2008)

Challenge: scaling up from organisms to ecosystems …..

Both adults and juveniles can be sensitive

Shellfish and corals are especially vulnerable

Some species more sensitive than others while some species seem invulnerable

Physiology and behaviour impacted in some species

Many sensitive species are directly or indirectly of great cultural, economic or biological importance

Gazeau 2007

LosersLosers(e.g. Green sea urchin, Dupont

& Thorndyke

2009)

WinnersWinners(e.g. Seastar

Crossaster

papposus, Dupont

et al 2010)

Within one Ecosystem, there could be Winners and Losers….

But both can have negative effect on marine ecosystems

CO2 Vents: “Windows” into High CO2 Ocean to Assess Ecosystem Impacts

Hall-Spencer et al. Nature (2008)

e.g. Sea grass benefit but so do invasive species – “winners and losers”

Studies in the shallow waters of the Mediterranean and deep-sea show:

- total loss of some calcareous species- reduced biodiversity- “regime shifts”: totally different ecosystems

Key links in the food chain show vulnerability….

Kawaguchi et al. 2010

360 ppm 2000 ppm

Pteropods shell growth

Arctic Limacina helicina stained with calcein. Calcification occurs near the shell opening (white rectangle). The arrow indicates the 5 days linear extent of the shell. 30% reduction of the calcification rate at pH 7.8. Comeau et al. (2009)

Krill embryo development

pH 8.09 pH 8.09

pH 7.8

Control550ppm700ppm850ppm

0

20

40

60

80

100

1 2 3 4Perc

ent t

i me

in p

r ed a

tor c

ue

Days in treatment

Fish Attracted to Smell of Predators ……..

Munday et al. 2010. PNAS 107 12930-12934

0

20

40

60

80

100

control 700ppm 850ppm

Perc

ent m

orta

lity

Hearing and balance may also be sensitive

Mortality 5-9 times higherConsequences for recruitment

• Strong geographic concurrence of continental shelves, upwelling and primary productivity and the amount of fish caught by fisheries.

• Areas vulnerable to early OA

• Vulnerability of aquaculture?

• Is the ‘blue revolution’ required to feed growing human population (6B to 9B by 2040) possible?

source: Sea Around Us project, October 2007 (University of British Columbia) Map designed by Hugo Ahlenius, UNEP/GRID- Arendal. http://maps.grida.no/go/graphic/world-fisheries- hotspots-2004

World’s Fisheries Hotspots ………………..

A Threat to Food Security

http://www.unep.org/dewa/pdf/Environmental_Consequences_of_Ocean_Acidification.pdf

Mounting Concern for Survival of Many Marine Organisms, Food Webs & Ecosystems.....

C. Turley

What will ocean ecosystems look like in a future high CO2 world?

And what will they be able to provide Mankind?

Ocean acidification may impact food security:

Indirectly through food webs

Directly on food providing organisms

Many countries depend nearly totally on fish as their main protein source

Mounting Evidence: that future CO2 emissions could impact some marine organisms and ecosystems this century

Turley et al. Marine Pollution Bulletin (2010)

Potential Vulnerabilities in Relation to Human Life spans – what it might mean to us and our children

-25

0

25

50

75

PRESENT

100

125

1985

2010

2035

2060

2085

2110

2135

atm CO2(ppm)

711

563

459

385

344 8.10

8.06

8.00

7.92

7.84

pHYears Date

828 7.78

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75%

95%

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)

Turley and Boot (in press) OUP Book on Ocean Acidification (Gattuso and Hansson eds.)

Sunset Over an Ocean with Man’s Footprint Now Detectable – Warmer, Less Diverse, Over Exploited……. And More Acidic

Oceans will become more acidic –

very high certainty.

The impact on ocean food webs, ecosystems & food security could be serious – less certain.

The only way of reducing the impact of global ocean acidification is a substantial and urgent reduction in CO2

emissions –

very high certainty.

Mitigation will make a difference

Joos et al. (2010)

The Challenge of Mitigation Scenarios for Ocean Acidification

•Large and rapid changes in ocean chemistry are underway now

•Stabilization requires large reduction in emissions.

•Emissions mitigation measures reduces ocean acidification compared to business-as-usual

• Trends can be persistent and impacts of carbon emissions may aggravate for decades and centuries, long after carbon emissions have been reduced

Mitigate ocean acidification = mitigate climate change

Change in thebaseline

Zachos et al.,Science 2005

Zachos et al.,ODP IR, 2003

Benthic foraminiferalmass extinction

Site 1262A

54.75

54.80

54.85

54.90

54.95

55.00

55.05

CaCO3 (wt%)

)aM(

egA

1500 m

3600 m

2600 m

20 40 60 80 1000

onset ofacidification

end ofacidification

• Mass extinctions linked to previous ocean acidification events

• Takes 10,000’s of years to recover

“Today is a rare event in the history of the World”

It has Happened Before in the Distant Past: And Offers Clues to Future Impacts?