1 Lesson: Ocean AcidificationMaury Project Lesson: Ocean Acidification 20 JUL 2015 Image Credit: NOAA NOS (http://oceanservice.noaa.gov/oceans/ohh/#1)

2 Today’s Objectives Review CO2 levels as a Greenhouse Gas to include its sources, sinks, atmospheric lifetime, and relative importance to radiative forcing Relate increasing atmospheric CO2 levels to Ocean pH. Discuss sources, sinks, rates, and transport pathways in the global carbon cycle and the relative timescales in for carbon cycling. Discuss anthropogenic alterations to the Global Carbon cycle to include deviations from steady-state. List the four major species of dissolved inorganic carbon in seawater that make up total dissolved organic carbon [SCO2]. Understand the thermal equilibrium reactions between [CO2], [H2CO3], [HCO3-], and [CO32-], in seawater. Know the relationship between [H+] and pH and the typical range for pH in seawater. Discuss how photosynthesis and respiration influence the pH of seawater. Differentiate between the lysocline and the calcium carbonate compensation depth (CCD).

3 Today’s Objectives List the four major species of dissolved inorganic carbon in seawater that make up total dissolved organic carbon [SCO2]. Understand the thermal equilibrium reactions between [CO2], [H2CO3], [HCO3-], and [CO32-], in seawater. Know the relationship between [H+] and pH and the typical range for pH in seawater. Discuss how photosynthesis and respiration influence the pH of seawater. Differentiate between the lysocline and the calcium carbonate compensation depth (CCD).

4 Today’s Objectives Know the relationship between solubility of calcium carbonate, shell formation and dissolution and pH. Define alkalinity, total alkalinity (TA), and carbonate alkalinity (CA). Write the major equilibrium reactions that influence the aqueous carbonate system. Mathematically relate CA, [SCO2], [HCO3-], [CO32-], [H+] and pH in seawater. Understand how photosynthesis, respiration, shell formation and shell dissolution affect [SCO2] and alkalinity in seawater. Discuss ocean acidification, its scale, and the potential impacts on marine organisms.

5 Earth as a Blackbody with AlbedoAssume incoming solar radiation reaches the Earth, 30% is reflected by the Earth’s albedo, and the rest reaches the surface and the Earth re-radiates it a Blackbody with no atmosphere: Use Stefan-Boltzmann Law to Solve for Earth’s Effective Surface Temperature: SWIN ↓ - (SWIN↓a) = SWIN↓(1-a) = SWNET↓ = LWOUT↑ = sTEARTH4 SWIN↓ = Average incoming solar radiation reaching the Earth (W/m2) LWOUT↑ = Average outgoing radiation leaving the Earth (W/m2) = x 10-8 Wm-2K-4 a = Earth’s Average Albedo = 31% TEARTH = Effective surface temperature of Blackbody Earth with no atmosphere TEARTH = 254K = -18 °C Actual TEARTH (avg.) ~ 288K (~ 15°C) → GREENHOUSE EFFECT (natural) +33°C!!!

6 Outgoing (Longwave) Radiation from the Earth – The Greenhouse EffectAbsorption – Energy is retained and converted Greenhouse Gases (GHGs) absorb outgoing longwave radiation at discreet energies and vibrate and rotate → heat the troposphere: CO2, H2O, CH4, N2O, CFCs, (O3*) Water vapor is the most important GHG in the Earth’s Atmosphere: High Relative Concentration Highly Variable Absorbs at Multiple Wavelengths Streete, 1991

7 Image created by Robert A. Rohde / Global Warming Art

8 Earth’s Radiation BalanceSW= Shortwave Solar Radiation Flux LW= Longwave Radiation Flux from the Earth SWIN↓ LW SW LW LW SW QNET = SWNET↓ + LWNET↑ @ Steady-State, QNET = 0 → 0 W/m2 = 235 W/m W/m2 SW SW LW Tropopause Scattering not shown… LW SW LW SW LW LW LW LW The mean annual radiant energy and heat balance of the Earth. From Fig 1.3, IPCC AR 2 WG 1, 1995; Houghton et al., 1996; Kiehl and Trenberth (1996).

9 Earth’s Mean Annual Radiation Budget - RevisitedHartmann, D.L., A.M.G. Klein Tank, M. Rusticucci, L.V. Alexander, S. Brönnimann, Y. Charabi, F.J. Dentener, E.J. Dlugokencky, D.R. Easterling, A. Kaplan, B.J. Soden, P.W. Thorne, M. Wild and P.M. Zhai, 2013: Observations: Atmosphere and Surface. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 159–254, doi: /CBO Hartmann, et al., IPCC AR5 WG1, 2013, Climate Change 2013: The Physical Science Basis, CH2, Fig. 2.11

10 The Radiative Forcing Concept (RF)Radiative Forcing (RF) = change in net energy (flux) at the Earth’s tropopause (DQNET) caused by a change imposed on the Earth’s Climate System; causes Climate Response, or change in the equilibrium condition of the Earth’s Climate System (i.e. DTSURF). According to the RF Concept, RF (+/- DQNET) can be related to a change in Earth’s Surface Temperature (+/- DTSURF) by the following equation: DTSURF = RF x l; Where, l = climate sensitivity parameter Strengths: Convenient first order measure of relative climatic importance of different climate forcing agents Computationally efficient/simple Relatively accurate Weaknesses: Assumes linearity of different forcing factors Does not handle climate system complexity well (i.e. feedback) Does not include climate parameters other than temperature Applies to global scale; not regional or less IPCC SAR, 1996; Ramaswamy et al., 2001; IPCC AR4 WG1 CH2, 2007.

11 Atmospheric Greenhouse Gases Increase in GR 2007–Present?Growth Rate (GR) of CO2: 1.66 ppm/yr since 1978 GR of CO2: 1.43 ppm/yr ’78-’95 1.91 ppm/yr 1995-Present GR of N2O 0.7 ppb/yr since 1978 GR of CH4: Decline in GR → Steady-State Increase in GR 2007–Present? GR of CFCs: Constant GR Decreasing GR Negative RG 2000-Present Figure 2. Global average abundances of the major, well-mixed, long-lived greenhouse gases - carbon dioxide, methane, nitrous oxide, CFC-12 and CFC-11 - from the NOAA global air sampling network are plotted since the beginning of These gases account for about 96% of the direct radiative forcing by long-lived greenhouse gases since The remaining 4% is contributed by an assortment of 15 minor halogenated gases (http://www.esrl.noaa.gov/gmd/aggi/)..

12 Mean annual atmospheric carbon dioxide growth rate at Mauna Loa Observatory, Hawaii (http://www.esrl.noaa.gov/gmd/ccgg/trends/#mlo_full)

13 Mean annual atmospheric carbon dioxide growth rate at Mauna Loa Observatory, Hawaii (http://www.esrl.noaa.gov/gmd/ccgg/trends/#mlo_full)

14 (Indirect effects as well…i.e. stratospheric H2O from CH4)IPCC AR5 WG1 SPM, Fig. SPM5 Volcanic Eruptions? Contrails? Hartmann, D.L., A.M.G. Klein Tank, M. Rusticucci, L.V. Alexander, S. Brönnimann, Y. Charabi, F.J. Dentener, E.J. Dlugokencky, D.R. Easterling, A. Kaplan, B.J. Soden, P.W. Thorne, M. Wild and P.M. Zhai, 2013: Observations: Atmosphere and Surface. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 159–254, doi: /CBO Changes in RF Factors (i.e. fossil fuel burning, deforestation) cause changes in RF Terms or Agents (LL-GHG’s, albedo) which has a direct effect on RF → Climate Response (Indirect effects as well…i.e. stratospheric H2O from CH4)

15 Effective “Atmospheric Lifetime” Time for Anthropogenic GHGsIPCC 2007 AR4 FAQ Effective Atmospheric Lifetime of a gas in the atmosphere is defined as the time it takes for a perturbation to be reduced to 37% of its initial amount = Time for an instantaeous pulse input to the atmosphere to decay to of its original value. For CO2 the specification of an atmospheric lifetime is complicated by the numerous removal processes involved → complex modeling of the decay curve. Accepted values ~ 100 years. Amounts of an instantaneous injection of CO2 remaining after 20, 100, and 500 years, used in the calculation of the Global Warming Potentials (GWPs) in IPCC (2007) AR 4.

16 Effective “Atmospheric Lifetime” Time for Anthropogenic GHGsIPCC TAR Table 1: Examples of greenhouse gases that are affected by human activities. [Based upon Chapter 3 and Table 4.1] CO2 (Carbon Dioxide) CH4 (Methane) N2O (Nitrous Oxide) CFC-11 (Chlorofluoro-carbon-11) HFC-23 (Hydrofluoro-carbon-23) CF4 (Perfluoro-methane) Pre-industrial concentration about 280 ppm about 700 ppb about 270 ppb 40 ppt Concentration in 1998 365 ppm 1745 ppb 314 ppb 268 ppt 14 ppt 80 ppt Rate of concentration change b 1.5 ppm/yr a 7.0 ppb/yr a 0.8 ppb/yr -1.4 ppt/yr 0.55 ppt/yr 1 ppt/yr Atmospheric lifetime 5 to 200 yr c 12 yr d 114 yr d 45 yr 260 yr >50,000 yr a Rate has fluctuated between 0.9 ppm/yr and 2.8 ppm/yr for CO2 and between 0 and 13 ppb/yr for CH4 over the period 1990 to b Rate is calculated over the period 1990 to c No single lifetime can be defined for CO2 because of the different rates of uptake by different removal processes. d This lifetime has been defined as an "adjustment time" that takes into account the indirect effect of the gas on its own residence time.

17 Perturbed Global Biogeochemical CycleCO2 Hartmann, et al., IPCC AR5 WG1, 2013, Climate Change 2013: The Physical Science Basis, CH6, Fig. 6.1

18 Cycling of Carbon DioxideShort-Term (100–102 yrs): Photosynthesis - Removes CO2 from the Atmosphere Respiration - Releases CO2 back into the Environment Fossil Fuel Combustion, Deforestation - Releases CO2 back into the Atmosphere Medium-Term (102–106 yrs): Photosynthesis/ Organic Carbon Burial, Sequestration in lithosphere and deep ocean - Removes CO2 from the Atmosphere MacKenzie,F.T. (2003) Long-Term (106+ years): Rock Weathering - Removes CO2 from the Atmosphere Marine Plankton Shell Formation, Plate Tectonics and Volcanoes - Releases CO2 back into the Environment Hartmann, et al., IPCC AR5 WG1, 2013, Climate Change 2013: The Physical Science Basis, CH6, Fig. FAQ6 2-1

19 Atmospheric Radiocarbon (14C)Exponential Decrease Over Time is Result of: Radioactive Decay of “Bomb Pulse” Equilibration w/ Land and Ocean Sink Input of Radiocarbon “Dead” Carbon from Fossil Fuel Burning

20 Atmospheric Stable Carbon Isotopes (d13C)Decreasing trend of -0.02‰/year in d13C towards more negative values indicative of inputs from fossil fuel burning Allison, C.E., R.J. Francey and P.B. Krummel. δ13C in CO2 from sites in the CSIRO Atmospheric Research GASLAB air sampling network, (April 2003 version). In Trends: A Compendium of Data on Global Change, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, TN, U.S.A.

21 Atmospheric GHGs – CO2 Hartmann, et al., IPCC AR5 WG1, 2013, Climate Change 2013: The Physical Science Basis, CH6, Fig. 6.8

22 Atmospheric CO2 Partitioning

23 Figure SPM.4 Multiple observed indicators of a changing global carbon cycleAll Figures © IPCC 2013 Figure SPM.4 | (b) partial pressure of dissolved CO2 at the ocean surface (blue curves) and in situ pH (green curves), a measure of the acidity of ocean water. Measurements are from three stations from the Atlantic (29°10’N, 15°30’W – dark blue/dark green; 31°40’N, 64°10’W – blue/green) and the Pacific Oceans (22°45’N, 158°00’W − light blue/light green). Full details of the datasets shown here are provided in the underlying report and the Technical Summary Supplementary Material. {Figures 2.1 and 3.18; Figure TS.5}

24 Why is it important to study carbon?Affects calcium carbonate dissolution and precipitation The carbon cycle helps maintain a constant pH in the ocean Scientists take samples from the center of the coral. Clipperton Atoll, 10°N, 109°W. Photo by Maris Kazmers (courtesy of th NOAA Image Gallery).

25 Dissolved Gases ↔ CO2 Air-Sea Interface CO2(gas) + H2O ↔ H2CO3(aq) ↕atmosphere CO2 Air-Sea Interface ↔ CO2(gas) + H2O ↔ H2CO3(aq) ocean ↕ H+(aq) + HCO3- ↕ 2H+(aq) + CO32–(aq)

26 Forms of Inorganic Carbon in SeawaterCO2(gas) + H2O ↔ H2CO3(aq) ↔ H+(aq) + HCO3- ↔ 2H+(aq) + CO32–(aq) Carbon is found in many forms in seawater: Dissolved CO2 gas (very little) H2CO3(aq) (very little) HCO3-(aq) CO32-(aq) Together these make up: total dissolved inorganic carbon [CO2] = [HCO3-] + [CO32-] [CO2(g)] + [H2CO3] +

27 Dissolved Gases ↔ N2 > O2 > Ar > CO2atmosphere N2 > O2 > Ar > CO2 Air-Sea Interface ↔ CO2, HCO3-, CO32- > N2 > O2 > Ar ocean

28 Dissolved Gases – CO2 Solubility of CO2 >> Solubility of O2, N2, Ar CO2(gas) + H2O ↔ H2CO3(aq) ↔ H+(aq) + HCO3- ↔ 2H+(aq) + CO32–(aq) Solubility coefficient:  with temperature  with salinity  with pressure As temperature, more CO2(gas) goes into solution Below thermocline, temperature constant; pressure controls CO2(gas) solubility As pressure, more CO2(gas) goes into solution According to Le Chatlier’s Principle, more CO2(gas) shifts equilibrium to produce more HCO3-(aq) and CO32–(aq) Very little CO2(gas) Mostly HCO3-(aq) and CO32–(aq)

29 CO2 with Depth SW, CH6, p. 114, Fig. 6.14a

30 pH of Seawater and the Aqueous Carbonate SystemSW, CH6, p. 114, Fig. 6.14b

31 pH of Seawater and the Aqueous Carbonate SystemStabilizes the pH of seawater Seawater average pH ~ 7.7; range We can use the change in [HCO3-]/[CO32-] to determine an increase or decrease in pH: HCO3- ↔ H+(aq) + CO32–(aq) K = ([H+]·[CO32-])/([HCO3-]) Where: K = 1* 10-9 mol/L → [H+] = K·([HCO3-] / [CO32-] ) pH= -log [H+]

32 Photosynthesis/Respiration and the pH of SeawaterCO2(gas) + H2O ↔ H2CO3(aq) ↔ H+(aq) + HCO3- ↔ 2H+(aq) + CO32–(aq) Surface waters in equilibrium with atm. Are slightly alkaline, pH = pH may rise through rapid extraction of CO2 during photosynthesis (~ 8.4+) Below the photic zone, net release of CO2 thru respiration, pH falls to avg. values ~ Can fall as low as 7.5 in anoxic conditions (sulphate reduction) Can rise as high as 12 in anoxic conditions (CO2 reduction) Photosynthesis → CO2 (gas) + H2O + (g energy + nutrients) → (CH2O)n + O2 (gas) ← Respiration CO2 (gas) + H2O + (thermal energy + nutrients) ← (CH2O)n + O2 (gas)

33 The Role of CaCO3 in Buffering SeawaterCaCO3(s) ↔ Ca2+(aq) + CO32-(aq) Surface Waters are Supersaturated with respect to calcium carbonate but spontaneous precipitation is infrequent due to inhibition from Mg2+ Shell Formation/Dissolution Ca2+(aq) + 2HCO3-(aq) → CaCO3(s) + CO2 + H2O Calcium + Bicarbonate  Calcium Carbonate + Carbon Dioxide + Water CaCO3(s) + H+ (aq) → Ca2+(aq) + 2HCO3-(aq) CaCO3(s) = Calcite and Aragonite; Aragonite dissolves more easily

34 Carbonate Compensation DepthCa2+ Extracted by Marine Organisms to Form CaCO3 Tests (Shells) m Sinking Skeletal Remains of Marine Organisms Sediments m Calcareous (CaCO3) ooze Depth at which significant dissolution of CaCO3 begins = LYSOCLINE m m Depth at which most or all of the CaCO3 has dissolved = CCD m Siliceous (SiO2) ooze

35 Lysocline and CCD Lysocline: depth at which significant dissolution of CaCO3 begins (Open University 1999) ~ the depth at which shell dissolution starts to have a detectable impact on the calcium carbonate content of the surface sediment (Libes 1992) Carbonate compensation depth (CCD): the depth at which most or all of the CaCO3 has dissolved (Open University 1999) ~ the depth at which the rate of calcite supply from the sinking of detrital shells is equal to their rate of loss by dissolution (Libes 1992)

36 Factors Affecting CaCO3 SolubilityFactors affecting calcium carbonate solubility: Temperature Pressure [CO2] [CaCO3] Particle size Flux

37 CCD DEPTHS Atlantic = ~ 5km Pacific = ~ 4,200-4,500 mWhy so different?

38 Carbonate Compensation DepthCO2+ H2O  H2CO3  HCO3- + H+  CO H+

39 CaCO3 Saturation Depths

40 CO2(gas) + H2O ↔ H2CO3(aq) ↔ H+(aq) + HCO3-Basic Equations/Equilibrium Reactions of the Aqueous Carbonate System that Influence Seawater pH CO2(gas) + H2O ↔ H2CO3(aq) ↔ H+(aq) + HCO3- ↔ 2H+(aq) + CO32–(aq) Carbon Dioxide + Water ↔ Carbonic Acid ↔ Hydrogen Ion + Bicarbonate ↔ Hydrogen Ion + Carbonate Ca2+(aq) + 2HCO3-(aq)  CaCO3(s) + CO2 + H2O Calcium + Bicarbonate  Calcium Carbonate + Carbon Dioxide + Water CaCO3(s) + H+ (aq)  Ca2+(aq) + 2HCO3-(aq) Calcium Carbonate + Hydrogen Ion  Calcium Ion + Bicarbonate Shell Formation → Shell Dissolution → Photosynthesis → CO2 (gas) + H2O + (g energy + nutrients) → (CH2O)n + O2 (gas) ← Respiration CO2 (gas) + H2O + (thermal energy + nutrients) ← (CH2O)n + O2 (gas)

41 Total for either equation yields a value ≈ 2 mol/m3Total Alkalinity The amount of acid required to neutralize all negative charges in seawater is the Alkalinity. Total Alkalinity (TA) - net molar concentration in ‘charge equivalents’ of the cations of strong bases in excess of the net molar concentration in ‘charge equivalents’ of the anions of strong acids in solution: TA = [cations of strong bases] - [anions of strong acids] = ([Na+] + [K+] + 2[Mg2+] + 2[Ca2+]) - ([Cl-] + 2[SO42-] + [Br-]) Or, in terms of conjugate pairs of weak acids and weak bases: TA = 2[CO32-] + [HCO3-] + [OH-] + [B(OH)4-] + [HPO42-] + 2[PO43-] + [H3SiO4-] + [NH3] + [HS-] + [NH3] + …- [H+] - [HSO4-] - [HF] - [H3] - … Total for either equation yields a value ≈ 2 mol/m3 ≈ 2[CO32-] + [HCO3-]

42 The Aqueous CO2/CaCO3 SystemShell Dissolution H +(aq) + CaCO3(s) HCO3-(aq) + Ca2+(aq)

43 Carbonate Alkalinity CA = 2[CO32-] + [HCO3-]The carbonate (CO32-) and bicarbonate (HCO3-) ion concentrations are much higher in seawater than the other carbon species, so we can approximate alkalinity by just using bicarbonate and carbonate ions: Carbonate Alkalinity (CA) = the total amount of hydrogen ions required to neutralize the negative charges of the carbonate and bicarbonate ions = the combined molar concentration of carbonate and bicarbonate ions, expressed in ‘charge-equivalent’ terms. CA = 2[CO32-] + [HCO3-]

44 CO2+ H2O  H2CO3  HCO3- + H+  CO32- + 2H+Carbonate Alkalinity The dissolution of calcium carbonate depends on [CO32-] which can be measured indirectly through the measure of [CO2] and alkalinity. Measured by titrating to find out how much H+ it takes to neutralize a solution CO2+ H2O  H2CO3  HCO3- + H+  CO H+

45 5. pH= -log [H+] CO2 , Alkalinity, and pH1. Carbonate Alkalinity (A or CA) = [HCO3-] + 2[CO32- ] 2. [CO2 ] = [CO2] + [H2CO3] + [HCO3-] + [CO32- ]; [CO2] + [H2CO3] << [HCO3-] + [CO32-] → [CO2 ] ~ [HCO3-] + [CO32- ] 3. A - [CO2 ] = [HCO3-] + 2[CO32-] - [HCO3-] - [CO32-] = [CO32-] 4. HCO3- ↔ H+(aq) + CO32-(aq) K = ([H+]·[CO32-])/([HCO3-]) Where: K = 1* 10-9 mol/L → [H+] = K·([HCO3-]/[CO32-]) 5. pH= -log [H+]

46 CO2 , Alkalinity, and pH In general: The greater [CO2], the smaller the value of A- [CO2] → greater [HCO3-] / [CO32-] → greater [H+] → lower pH

47 Total Dissolved Inorganic Carbon (CO2 )[ΣCO2] is affected by photosynthesis, respiration, and CaCO3 formation/ dissolution E. huxlei bloom near Sweeden, May, 2010

48 Alkalinity Not affected by photosynthesis/ respiration, but is affected by CaCO3 formation/ dissolution Why? Pteropod- a zooplankter that makes a CaCO3 shell

49 CO2 , Alkalinity, and pH SW, CH6, p. 119, Fig. 6.15

50 3.3 Impacts of Future Climate Change3. Climate change and its impacts…under different scenarios 3.3 Impacts of Future Climate Change Ocean Acidification: The marine carbonate buffer system allows the ocean to take up CO2 far in excess of its potential uptake capacity based on solubility alone, and in doing so controls the pH of the ocean: (1) CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3- ↔ 2H+ + CO32– (2) CO2 + H2O + CO32– ↔ HCO3- + H+ + CO32– ↔ 2HCO3- Net effect of more CO2: More H+ and HCO3- Less CO32– CaCO3 + CO2 + H2O ↔ Ca2++ 2HCO3- IPCC, 2007, AR4, WG1, Ch. 7

51 3.3 Impacts of Future Climate Change3. Climate change and its impacts…under different scenarios 3.3 Impacts of Future Climate Change Ocean Acidification: Estimated Changes in pH of Ocean Surface due to Human CO2 Emissions During Industrial Period ( ) Ocean acidification may have negative impacts on ocean organisms, and thereby on rest of environment, human activities, food resources, etc. Figure from: GW Talk, Tom Murphree, Dec09,

52 Impacts of Ocean AcidificationOrganisms must expend more energy to produce shells

53 Impacts of Ocean AcidificationOrganisms must expend more energy to produce shells The pteropod, or “sea butterfly”, is a tiny sea creature about the size of a small pea. Pteropods are eaten by organisms ranging in size from tiny krill to whales and are a major food source for North Pacific juvenile salmon. The photos below show what happens to a pteropod’s shell when placed in sea water with pH and carbonate levels projected for the year The shell slowly dissolves after 45 days.  Photo credit: David Liittschwager/National Geographic Stock. Used with permission. All rights reserved. National Geographic Images.

54 CO2 , Alkalinity, and pH in TropicsHow does temperature affect Total Dissolved Inorganic Carbon [ΣCO2]? As temperature goes up, the solubility of CO2↓ → [ΣCO2]↓ How does temperature affect carbonate alkalinity? → (CA - [ΣCO2])↑ → [CO32-]↑ If [CO32-]↑↑; more precipitation of CaCO3 (spontaneous precipitation…) → alkalinity↓ In short, if temperature affects calcium carbonate solubility, it affects alkalinity….

55 Coral Reefs - CarbonateTropical corals are heterotrophic invertebrate animals (Phylum Cnidaria) that live in symbiosis with a photosynthetic dinoflagellate (Kingdom Protista) Tropical reef-building corals cannot tolerate water temps <18°C. Grow optimally in water temps 23°-29°C. Some can tolerate temps as high as 40° C for short periods. Most also require very saline (salty) water pH? Other? Coral Bleaching - Corals are stressed by changes in conditions such as temperature, light, or nutrients → breakdown of symbiosis with photosynthetic dinoflagellate (Kingdom Protista) → symbiont leaves host or is expelled → animal host dies…characterized by brown-white skeletal remains…

56 Questions? Joseph P. Smith, Ph.D. Oceanography DepartmentU. S. Naval Academy 572C Holloway Road, 9D Annapolis, MD Tel: