Possible Consequences of Global Warming and Ocean ... · Possible Consequences of Global Warming...

19
Possible Consequences of Global Warming and Ocean Acidification on Marine Ecosystems Victoria J. Fabry California State University San Marcos

Transcript of Possible Consequences of Global Warming and Ocean ... · Possible Consequences of Global Warming...

Page 1: Possible Consequences of Global Warming and Ocean ... · Possible Consequences of Global Warming and Ocean Acidification on Marine Ecosystems Victoria J. Fabry California State University

Possible Consequences of Global Warming and Ocean

Acidification on Marine Ecosystems

Victoria J. Fabry California State University San Marcos

Page 2: Possible Consequences of Global Warming and Ocean ... · Possible Consequences of Global Warming and Ocean Acidification on Marine Ecosystems Victoria J. Fabry California State University

Climate Forcing: Rising ocean temperature and pCO2

• More stratified• Lower nutrient

availability • Decreased oxygen• Lower pH• Lower [CO3

2-]• Lower carbonate

saturation state

Ecosystem Effects• Productivity• Species succession• Food webs • Fisheries• Species abundances

and biogeography• Biodiversity• Air-sea gas

exchange• Biogeochemical

cycles (C, N, S, P)• Feedbacks to climate

Physiological Effects• Photosynthesis• Calcification • N-fixation• Metabolism• Growth• Reproduction • Tolerance to other

environmental fluctuations

• Fitness and survival

The Changing Ocean: Warmer and More Acidic

Uncertainties great – research required

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Examples:

1. Decline in Antarctic Krill

2. Coral Bleaching

3. Ocean Acidification

4. Mitigation and Adaptation

Victoria Fabry, Richard A. Feely, Mark Victoria Fabry, Richard A. Feely, Mark EakinEakin, and , and Chris LangdonChris Langdon

Page 4: Possible Consequences of Global Warming and Ocean ... · Possible Consequences of Global Warming and Ocean Acidification on Marine Ecosystems Victoria J. Fabry California State University

Atkinson et al., 2000

Krill Krill

Salps

Decline in Krill Stocks in Southern OceanKrill distributions:• need both summer

phytoplankton and winter ice algae

• spatial correlation with chlorophyll;

• temporal correlation with winter sea-ice extent

• Western Peninsula –winter sea ice duration is decreasing

• May see future regime shift from krill dominated to salpdominated system

Ducklow et al., 2007

Page 5: Possible Consequences of Global Warming and Ocean ... · Possible Consequences of Global Warming and Ocean Acidification on Marine Ecosystems Victoria J. Fabry California State University

Salps

Implications for Antarctic Food

WebSalps: • Carbon-poor food

source; not preferred prey of higher trophiclevels

• Fast generation times• Associated with lower

latitudes

L. Madin

Page 6: Possible Consequences of Global Warming and Ocean ... · Possible Consequences of Global Warming and Ocean Acidification on Marine Ecosystems Victoria J. Fabry California State University

Abnormally warm water temperatures are one of the major causes of massive coral reef bleaching in recent years

Coral Bleaching

Under certain environmental stresses, colorful symbiotic algae (zooxanthallae) which live in coral body are expelled by the transparent host coral

the white coral calcium carbonate skeleton is exposed

Healthy Corals Bleached Corals

Page 7: Possible Consequences of Global Warming and Ocean ... · Possible Consequences of Global Warming and Ocean Acidification on Marine Ecosystems Victoria J. Fabry California State University

19951998

Widespread bleaching in Belize(from Aronson and Precht 1997, 2001)

1999

Provided by Mark Eakin

Catastrophic, Unprecedented Coral Bleaching

Page 8: Possible Consequences of Global Warming and Ocean ... · Possible Consequences of Global Warming and Ocean Acidification on Marine Ecosystems Victoria J. Fabry California State University

Operational Bleaching HotSpots and Degree Heating Weeks (DHW)

SST

TimeWeek-0 Week-12

Bleaching threshold (MMMSST+1ºC)

Maximum Monthly Mean SSTClimatology (MMMSST)

HotSpots

Degree Heating Weeks

(HotSpot value × duration)12 weeks

≥ 1°C

≥ 4 DHWs → coral bleaching is expected≥ 8 DHWs → mass bleaching and mortality are expected

bb ccaa ddMidway Atoll, US28.3N, 177.4W

12 week accumulation todayMax 12WKCurrent Temp (°C)Exp. Max Temp

0.02(99)27.226.9

Pro

vide

d by

Mar

k E

akin

Page 9: Possible Consequences of Global Warming and Ocean ... · Possible Consequences of Global Warming and Ocean Acidification on Marine Ecosystems Victoria J. Fabry California State University

NOAA Degree Heating WeeksNOAA Degree Heating WeeksHighest Caribbean Stress in 21 YearsHighest Caribbean Stress in 21 Years

1 Degree 1 Degree Heating Heating Week Week (DHW) = 1°C (DHW) = 1°C above above maximum maximum monthly monthly mean mean for 1 for 1 weekweek

≥ 4 DHWs → coral bleaching is expected≥ 8 DHWs → mass bleaching and mortality are expected

Provided by Mark Eakin

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Ocean Acidification

Caldeira & Wickett (2003)

Ocean uptake of anthropogenic CO2 is lowering the pH in the surface ocean

Today’s surface waters are

slightly alkaline

Future surface waters will be less alkaline

Rate of change is probably 100 times faster than that which occurred at end of recent ice ages

By 2100,the pH of surface water could drop by 0.3 to 0.5 units relative to the pre-industrial value

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Nancy Sefton

Diversity of Calcifiers

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-50

50

100

150

200

050100150200250300350400450Carbonate ion concentration (µmol kg-1)

Cora

l Cal

cifi

cati

on r

ate

mm

olm

-2d-

1

Net Dissolution

Net Calcification

1870

280

2006

380

Low CO2 High CO2

-50

50

100

150

200

00

CO2 level inAtmosphere

(ppm)

Glacial

180 560

COCO22

2X2X

840

COCO22

3X3X

Evidence suggests a linear decrease in the calcification rate of coral reef systems with decreasing carbonate

ion concentrations

R2 = 0.843

Langdon & Atkinson, (2005)

Time

Page 13: Possible Consequences of Global Warming and Ocean ... · Possible Consequences of Global Warming and Ocean Acidification on Marine Ecosystems Victoria J. Fabry California State University

Some Corals Can Survive and Recover from Decalcification

Fine & Tchernov, 2007

• Grown in corrosive water (pH 7.3 to 7.6) conditions for 12 months

•Skeleton dissolved & colony dissociated into anemone-like polyps

•When returned to normal pH, calcified & reformed colonies

• Predation on exposed polyps?

• Loss of reef structure would cause major changes in ecosystem services

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pCO2 280-380 ppmv pCO2 780-850 ppmv

Emiliania huxleyi

Riebesell et al.(2000); Zondervan et al.(2001)

Gephyrocapsa oceanica

CoccolithophoresCoccolithophores

Calcification decreased

- 9 to 18%

- 45%

Some coccolithophore species not sensitive to increased CO2

Page 15: Possible Consequences of Global Warming and Ocean ... · Possible Consequences of Global Warming and Ocean Acidification on Marine Ecosystems Victoria J. Fabry California State University

Shells of living pteropods begin to Shells of living pteropods begin to dissolve at elevated COdissolve at elevated CO22 levelslevels

Whole shell: Clio pyramidata Arag. rods exposed

Prismatic layer (1 µm) peels back

Aperture (~7 µm): advanced dissolution

Normal shell: unexposedto undersaturated water

(Orr et al., 2005)

In polar & subpolar regions:• Pteropod populations high (reaching >1000/m3)• Abundant food source for marine predators (including salmon,

pollock & other fish)• Integral component of food webs• Can be important in biogeochemical cycles (C, S)

R. Hopcroft

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• Adverse effects on reproductive success-Decreased fertilization rates (sea urchins, bivalves)-Increased juvenile mortality (bivalves, sea urchins, copepods, fish larvae)

• Reduced growth in adults (sea urchins, bivalves)

• Impaired oxygen transport and scope for activity (squid)

• Increased rates of N-fixation (potential for major changes in algal abundances and nutrient limitation)

Evidence for Other Ocean Acidification Impacts

Page 17: Possible Consequences of Global Warming and Ocean ... · Possible Consequences of Global Warming and Ocean Acidification on Marine Ecosystems Victoria J. Fabry California State University

Mitigation and Adaptation

Mitigation• Decrease CO2 emissions• Iron fertilization• Direct injection of CO2

into deep water • Seawater electrolysis• Urgency

10-20 year window (Stern Report, 2006; Hansen et al., 2006)

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Mitigation and Adaptation

Adaptation (Coping)• Reef Manager’s Guide to

Coral Bleaching (NOAA, EPA, Australia Great Barrier Reef Park Authority)

• Rear potentially vulnerable juvenile stages under controlled conditions

• Re-populate impacted areas with resistant species Research required

Page 19: Possible Consequences of Global Warming and Ocean ... · Possible Consequences of Global Warming and Ocean Acidification on Marine Ecosystems Victoria J. Fabry California State University

Thank you