Climate Change and Coral Reefs

Transcription

1 Climate Change and Coral Reefs Joan A. Kleypas National Center for Atmospheric Research Boulder, CO EARTH Robert W. Buddemeier Kansas Geological Survey University of Kansas Lawrence, KS EARTH SeaWiFS image from: Orbimage

2 Historical Records of modern H. sapiens 1 st human artwork early civilization Atm. CO 2 Concentration Sources: Petit et al Pearson & Palmer 2000 Royer et al Demicco et al. 2003

3 Effects of CO 2 on Coral Reefs Increased Atmospheric CO 2 Increased Atmospheric Temperature Climatic Changes Altered storm frequency/ intensity Increased dust (Fe fertilization) Reduced [CO 3 2- ] Increased sea surf. temp. Sea level rise Reduced Calcification Increased Bleaching Differential Impacts Increased Breakage & Erosion Reduced Light

4 Distribution of Reefs vs Sea Surface Temperature Minimum SST C Maximum SST C

5 Distribution of Reefs vs Sea Surface Temperature

6 Potential Poleward Expansion of Coral Reefs Present Region > 18 C

7 Potential Poleward Expansion of Coral Reefs Future Region > 18 C Warming derived from CCSM scenario runs

8 Temperature & Coral Stress Episodic warming An increase in maximum temperature Coral bleaching due to algal stress Chronic warming An increase in average temperature Coral bleaching due to physiological stress (thinning of coral tissues) Coral disease Death toll : 15% of coral reefs worldwide destroyed by bleaching. L. Devantier

9 Coral Bleaching A breakdown of coral-algal symbiosis Factors: 82/83 El Niño Temperature Light Circulation Insert graph here 97/98 El Niño

10 Coral Bleaching Reports mild moderate high

11 Bleaching Thresholds & Adaptation Hughes et al. Science 2003

12 Annual Max SSTs HADISST observations T adapt = 25y T adapt = number of years required for a coral to adapt to SST after Ware, 1997

13 Annual Max SSTs HADISST observations T adapt = 25y * Mild bleaching * Moderate bleaching * Severe bleaching

14 Annual Max SSTs HADISST observations CCSM 1.0 control T adapt = 25y * Mild bleaching * Moderate bleaching * Severe bleaching

15 Annual Max SSTs HADISST observations CCSM 1.0 control CCSM 1.0 A1 SRES T adapt = 25y * Mild bleaching * Moderate bleaching * Severe bleaching

16 Annual Max SSTs HADISST observations CCSM 1.0 control CCSM 1.0 A1 SRES T adapt = 50y * Mild bleaching * Moderate bleaching * Severe bleaching

17 Coral Disease Reports First Descriptions: 1970s Black-band Disease 1970s White-band Disease 1977 White Plague 1994 Yellow-blotch/Yellow-band 1996 White Pox 1997 Red Band Disease???? Dark Spots Disease Source: ReefBase Factors: Pollution Human-caused introduction Increasing temperature

18 Coral Disease Reports A. Bruckner A. Bruckner

19 HADISST comparison of max SSTs

20 Effects of CO 2 on Coral Reefs Increased Atmospheric CO 2 Increased Atmospheric Temperature Climatic Changes Altered storm frequency/ intensity Increased dust (Fe fertilization) Reduced [CO 3 2- ] Increased SST Sea level rise Reduced Calcification Increased Bleaching Differential Impacts Increased Breakage & Erosion Reduced Light

21 Carbonate Chemistry CO 2 photosynthesis respiration CO 2 aq (CO 2 + H 2 O) H 2 CO 3 Carbonic acid Alkalinity bicarbonate HCO 3 + H + Proportion of HCO 3 Mg 2+ Na + and CO 2 3 adjusts to balance alkalinity K + Ca 2+ carbonate CO H + [CO 3 2 ]= ALK TCO 2 CaCO 3 calcification

22 Carbonate Chemistry 1xCO 2 2xCO 2 CO photosynthesis respiration CO 2 aq (CO 2 + H 2 O) H 2 CO 3 Carbonic acid 8 16 Alkalinity bicarbonate HCO 3 + H Mg 2+ Na + K + Ca 2+ carbonate CO H TCO 2 CaCO 3 calcification ph Ω-arag Ω = [CO 3 2- ][Ca 2+ ]/K sp arag

23 [CO 3 2 ] versus pco 2 and SST Glacial through Preindustrial Carbonate ion Concentration (µmol kg -1 )

24 [CO 3 2 ] versus pco 2 and SST Present through 2xCO 2 Carbonate ion Concentration (µmol kg -1 )

25 Coccolithophores Forams calcite calcite T. Tyrrel Calcareous algae Corals High-Mg calcite Christa Farmer aragonite Nancy Sefton NOAA

26 Calcification versus [CO 3 2 ] - corals and coral communities - Marubini et al Langdon et al Leclercq et al. 2000

27 [CO 3 2- ] at 280 ppmv and 560 ppmv

28 CaCO 3 Budget Organism calcification Imported CaCO 3 CaCO 3 addition: + + Inorganic Cementation CaCO 3 removal: Export + Dissolution Ca 2+ CO3 2

29 Processes in Reef CaCO 3 Accumulation T Ca 2+ CO 3 2 Organism calcification Net reef accumulation

30 Processes in Reef CaCO 3 Accumulation Net reef accumulation

31 Model of Reef Growth versus Sea Level Rise drowned/ sediment massive branching 1 branching m seafloor Graphics by NCAR Visualization Lab

32 Coral Calcification versus Reef Calcification CORALS biology/ecology Lower CaCO 3 production: Weaker and/or slower growing? Less competitive for space on reef? More susceptible to damage? Other Ecosystems REEFS geology Lower CaCO 3 production/cementation and higher CaCO 3 dissolution: Reef CaCO 3 budget reduced Loss of reefs, atolls, coral cays?

33 Climate System Changes Smooth Reef Response Gradual Erratic Thresholds Bleaching, etc. Disease outbreaks Phase shifts (coral algal) Surprises???

34 Rapid Climate Change from: Alley et al Science

35 Climate System Changes Smooth Reef Response Gradual Erratic Thresholds Bleaching, etc. Disease outbreaks Phase shifts (coral algal) Surprises???

36 Climate System Changes Smooth Reef Response Gradual Erratic Surprises Thresholds Bleaching, etc. Disease outbreaks Phase shifts (coral algal)???

37 Climate System Changes Smooth Reef Response Gradual Erratic Thresholds Bleaching, etc. Disease outbreaks Phase shifts (coral algal) Surprises???

38 Conclusions Projected changes in climate will drive temperature and seawater chemistry to levels outside the envelope of modern reef experience This hinders our ability to predict how coral reefs will respond in the future We should expect surprises in how coral reefs will respond: Surprises have already occurred Climate surprises are likely Our best predictions are that climate change will lead to major changes in coral reef ecosystems, both biologically & geologically Species assemblages will be pulled apart Geological functioning of reefs will change ARVAM

39 Credits Photographs/Graphics ARVAM Richard Alley Lyndon DeVantier Christa Farmer Terry Hughes Eric TJT Kwint Jamie Oliver Nancy Sefton NOAA ReefBase Toby Tyrrell Brainpower Rich Aronson Bill Fitt John Guinotte Don Middleton Eric TJT Kwint