Impact of ocean acidification on Hawaiian coral reefs in the 21st century.

Transcription

1 Impact of ocean acidification on Hawaiian coral reefs in the 21st century. Paul L. Jokiel, Ku ulei ulei S. Rodgers Hawaii Coral Reef AssesmentAssessment and Monitoring Program (CRAMP) Hawai i Institute of Marine Biology (HIMB)

2 Ilsa B. Kuffner U.S. Geological Survey, St. Petersburg, Florida Andreas J. Andersson Bermuda Institute of Ocean Sciences Fred T. Mackenzie University of Hawai i, Department of Oceanography Evelyn F. Cox Hawaii Institute of Marine Biology Bob Buddemeier University of Kansas

3 Mesocosm Facility, HIMB

4 Major Features: Mesocosm Experimental Design Replicated (much previous work used treatment n=1) Continuous flow, live seawater, rapid (1h) turnover Long term experiment (10 months) Natural irradiance regime Natural diurnal and seasonal variability (temperature, irradiance, sea water chemistry, etc.) Realistic biological environment Present day pco 2 vs. 2 X present pco 2

5 Measured: Coral growth and mortality Montipora capitata (Buoyant weighing at various intervals, branch extension by alizarin stain technique) Coral spawning Montipora capitata Coral recruitment Pocillopora damicornis Recruitment and growth of algae on removable plastic cylinders (Feb-Mar 2006). and on mesocosm walls (Nov Aug 2006) Growth of rhodoliths (Nov Aug 2006) Recruitment of other calcifying organisms on walls Net Ecosystem Calcification (NEC)

6 Duration: Oct 2005 Aug 2006 Flow 8 liters min -1, turnover 1 h 3 treatment, 3 control randomly assigned. Acidified treatment: 10% solution (HCl) diluted with tap water injected into inflow pipe at 1.3 ml min -1 using a multi-channel peristaltic pump. Control treatment: plain tap water pumped at the same rate.

7 Seawater chemistry. squares = acidified circles = control Left column average midday seawater carbonate chemistry. (mean increase pco 2 =365±130 µatm atm) Right column diurnal cycle ( June 21-22, 22, 2006) Jokiel et al. (2008)

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9 Feb-Mar 2006 Non-calcifying algae +52% CCA recruits 78% CCA Cover 92% Kuffner IB, Andersson AJ, Jokiel PL, Rodgers KS, Mackenzie FT (2008) Decreased abundance of crustose coralline algae due to ocean acidification. Nature Geoscience 1:

10 No mortality Coral calcification rate reduced 15-20% Skeletal density decreased, branches thinner No evidence of acclimation The calculated decrease in CaCO 3 production, estimated using the scenarios considered by the International Panel on Climate Change (IPCC), is 10% between 1880 and 1990, and 9-30% (mid estimate: 22%) from 1990 to (Gattuso et al. 1999).

11 Recruitment Control mean±1 s.e. Acidification mean ±1 s.e. Percent Difference Two-sample t-test test Rhodolith accretion (g buoyant weight yr -1 ) + 0.6± ± P<0.0001

12 Mesocosm Wall Settlements Recruitment Control mean±1 s.e. Acidification mean ±1 s.e. Percent Difference Two-sample t-test Crustose coralline algae (% cover on walls) 25± ± p = 0.03 Turf algae (% cover on walls) 16.6± ± p = 0.69 Vermetid tubes (no. per m 2 ) Serpulorbis sp. 78.4± ± p = 0.18 Oyster % cover Dendrostrea sandwichensis 5.7± ± p = 0.56 Barnacles (no. per m 2 ) Balanus sp. 8.3± ± p = 0.37 Barnacle size (mm) Balanus sp. 5.1± ± p = 0.25 Bare Substratum (% cover on walls) 53.2± ± p= Jokiel et al. 2008

13 Settlements of reef coral Pocillopora damicornis Control Mean ±1 s.e. Acidification Mean ±1 s.e. Percent Change Two-sample t-test Settlements per m 2 55±14 49±18-11 p = 0.81 Diam. (mm) 2.5± ± p = 0.44 no. of polyps per settlement 4.4± ± p = 0.47 Jokiel et al Consistent with: Albright, Mason and Langdon (2008)

14 Measured Variable Control ±s.e. Acidified ±s.e. Percent Difference Statistical Significance bundles g 1 coral eggs bundle ± ± ± ± p = 0.47 p = 0.06 Jokiel et al Photo: Waikiki Aquarium Consistent with Fine and Tchernov (2007)

15 June 21-22, 22, 2006 Net Ecosystem Calcification (NEC = CaCO 3 production - dissolution) +4.5 mmol CaCO 3 h 1 At present seawater pco mmol CaCO 3 h 1 At twice present pco 2 CORALS WILL STILL BE GROWING WHILE REEFS ARE DISSOLVING! Andersson, Andreas J., Ilsa B. Kuffner, Fred T. Mackenzie, Paul L. Jokiel, and Ku ulei S. Rodgers. Adrian Tan (2009) Net loss of CaCO3 from coral reef communities due to human induced seawater acidification. Biogeosciences Discuss., 6, 1 20, 2009.

16 Present day Hawaiian coral reefs Porites Pocillopora Montipora

17 Response of Hawaiian corals to increased temperature.

18 Dead Pocillopora Bleached Porites Montipora eliminated

19 Changes in aragonite saturation predicted to occur as atmospheric CO 2 concentrations (ppm ppm) increase. Hoegh-Guldberg et al. (2007). Science 318:

20 Predicted Changes in Coral Cover, Hawaii Buddemeier, R. W., P.L. Jokiel, K.M. Zimmerman, D.R. Lane, J. M. Carey, G.C. Bohling, J.A. Martinich. (2008) A modeling tool to evaluate regional coral reef responses to changes in climate and ocean chemistry Limnol Oceanogr. Meth. 6:

21 Maro Reef - Crustose Coralline Reef Formation Photo by Paul Jokiel

22 Hawaiian coral reef of the future.

23 Dissolved / eroded coral skeleton Bleached Porites Dead Pocillopora skeletons Exposed basalt Montipora eliminated

24 We must consider related factors:

25 More fragile skeletons- Increasing storm waves

26 Sea level rise increased sedimentation

27 Increased pollution and overfishing.

28 CONCLUSIONS Ocean acidification will primarily impact calcification and dissolution of calcium carbonate with substantial differences in response between various taxonomic groups. Coral calcification will decrease due to increasing ocean acidification but the impact on crustose coralline algae calcification will be much more severe. Bleaching and coral mortality events are highly visible, but the insidious degradation of reefs due to ocean acidification, pollution, sedimentation and overfishing must be considered in forecasting the future of coral reefs and in management actions.

29 COMMENT We have the knowledge, technology and resources needed to reduce and eliminate CO 2 emissions from fossil fuel and manage other anthropogenic impacts. What will our species do with this information?

30 C'est la vie!