C

The Effect of Ocean
Acidification on
Calcification in
Calcifying Algae, Corals,
and Carbonate-dominated Systems

image

This appendix serves as an example of the wide variety of experimental studies on the effects of ocean acidification on calcifying marine organisms. We focus here on calcifying algae, corals, and carbonate-dominated systems, because more studies have been conducted on this collective group than on others. This table lists only those studies published through 2009 that used realistic carbonate chemistry manipulations; i.e., those that were consistent with projected changes in the carbonate chemistry of seawater due to natural forcing. Note that pCO2 is reported both in units of parts per million (ppm) and microatmospheres (μatm); the two units can be considered essentially equivalent.



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C The Effect of Ocean Acidification on Calcification in Calcifying Algae, Corals, and Carbonate-dominated Systems This appendix serves as an example of the wide variety of experimen tal studies on the effects of ocean acidification on calcifying marine organ isms. We focus here on calcifying algae, corals, and carbonatedominated systems, because more studies have been conducted on this collective group than on others. This table lists only those studies published through 2009 that used realistic carbonate chemistry manipulations; i.e., those that were consistent with projected changes in the carbonate chemistry of sea water due to natural forcing. Note that pCO2 is reported both in units of parts per million (ppm) and microatmospheres (atm); the two units can be considered essentially equivalent.

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APPENDIXC Organism/ System Summary of findings Reference Calcifying Algae Crustose Manipulation: Acid addition Kuffner et al., coralline algae Duration: 7 weeks 2008 (unidentified Design: Outdoor continuousflow species) mesocosms: control at ambient reef pCO2 (average 380 ppm), others manipulated to ambient + 365 ppm. Recruitment and growth of crustose coralline algae were measured on clear acrylic cylinders after 7 weeks in control and manipulated flumes. Results: Under high CO2 conditions, CCA recruitment rate decreased by 78% and percentage cover decreased 92% relative to ambient; noncalcifying algae percent cover increased by 52% relative to ambient. Rhodoliths of Manipulation: Acid addition Jokiel et al., mixed crustose Duration: 9 months 2008 coralline algae Design: Outdoor continuousflow including mesocosms: control at ambient reef pCO2 Lithophyllum (average 380 ppm), others manipulated to cf. pallescens, ambient + 365 ppm. Rhodolith growth was Hydrolithon sp. measured with buoyant weighing. and Porolithon sp. Results: Rhodolith growth in control mesocosms was 250% lower than those in acidified mesocosms; that is, they experienced net dissolution. Porolithononkodes Manipulation: Bubbled CO2 Anthony et al., Duration: 8 weeks 2008 Design: Algae placed in flowthrough aquaria: 2 temperatures: 2526C and 2829C; 3 pH levels: 8. 08.4 (control) 7.857.95 and 7.607.70. Results: P. onkodes calcification rate in low pH treatment was 130% less (2526C) and 190% less (2829C) than in control (i.e., net dissolution).

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APPENDIXC Organism/ System Summary of findings Reference Calcareous Manipulation: Bubbled CO2 and field Martin et al., epibionts on observations 2008 seagrasses Duration: 2 weeks (Hydrolithon Design: In field, calcium carbonate mass boreale,H. on seagrass blades was measured across a cruciatum, natural pH gradient. In lab, seagrass blades H.farinosum, with 5070% cover of crustose coralline algae Pneophyllum were collected from the field and placed in confericola,P. aquaria of pH = 8.1 (control) or pH = 7.0. fragile andP. Coralline algal cover was estimated before zonale) and after treatments. Results: In field, coralline algal cover was highly correlated with pH, decreasing rapidly below pH = 7.8 and absent at pH = 7.0; in lab experiment, coralline algae were completely dissolved after two weeks at a pH of 7.0, whereas control samples showed no discernable change. Rhodoliths of Manipulation: Both acid/base addition and Semesi et al., Hydrolithon sp. bubbled CO2 2009a Duration: 5 days Design: Acid/base additions used to alter pH to multiple levels (7.6, 7.8, 8.2, 8.6, 9.0, 9.4 and 9.8; control was 8.1); CO2 bubbling used to alter pH and DIC to 7.8. Results: Calcification rate was positively correlated with pH in both light and dark experiments; decreasing the pH to 7.8 with CO2 bubbling lowered calcification by 20%. Hydrolithon sp. Manipulation: Drawdown of CO2 by seagrass Semesi et al., Mesophyllym sp. photosynthesis 2009b Halimedarenschii Duration: 2.5 hours Design: In situ openbottom incubation cylinders; pH and algal calcification rates measured in presence or absence of seagrasses. Results: Seagrass photosynthesis caused pH to increases from 8.38.4 to 8.68.9 after 2.5 hours; calcification rates increased > 5x for Hydrolithon sp., and 1.6x for Mesophyllum sp. and Halimeda sp.

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APPENDIXC Organism/ System Summary of findings Reference Lithophyllum Manipulation: Bubbled CO2 Martin and cabiochae Duration: 1 year Gattuso, 2009 Design: Algae were maintained in aquaria at ambient or elevated temperature (+3C) and at ambient (~400 ppm) or elevated pCO2 (~700 ppm). Results: No clear pattern of reduced calcification at elevated pCO2 alone, but combination of elevated pCO2 and temperature led to high rates of necroses and death. The dissolution of dead algal thalli at elevated pCO2 was 24x higher than under ambient pCO2. Corallinasessilis Manipulation: Bubbled CO2 Gao and Zheng, Duration: 30 days 2009 Design: Controlled laboratory experiments to investigate the interactive effects of pCO2 and UV radiation on growth, photosynthesis, and calcification. 2 pCO2 levels (280 and 1000 ppmv), combined with 3 light conditions: PAR alone (solar radiation wavelengths > 395 nm); PAR+UVA (> 320 nm); PAR+UVA+UVB (> 295 nm). Results: Under PAR alone, elevated pCO2 decreased net photosynthetic rate by 29.3%, and calcification rate by 25.6% relative to low pCO2. Elevated pCO2 exacerbated the effects of ultraviolet radiation in inhibiting rates of growth (from 13% to 47%), photosynthesis (from 6% to 20%), and calcification (from 3% to 8%). The authors suggest that the decrease in calcification in C.sessilis at higher pCO2 levels increases its susceptibility to damage by UVB radiation. Halimedaincrassata Manipulation: CO2 bubbling Ries et al., 2009 (green alga) and Duration: 60 days Neogoniolithon Design: Controlled laboratory experiment spp. (coralline red to examine changes in calcification alga) under arag = 3.12, 2.40, 1.84, and 0.90 (approx. pCO2 = 409, 606, 903, 2856 ppmv, respectively). SST maintained at 25C. Results: Calcification rates in both species were higher at arag = 2.40, then declined at lower saturation states.

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APPENDIXC Organism/ System Summary of findings Reference Corals Stylophora Manipulation: Altered Ca2+ ion Gattuso et al., pistillata concentration1 1998 Duration: 2.5 hours Design: Controlled laboratory experiment; aragonite saturation changes from 98 to 390% were obtained by manipulating the calcium concentration. Results: Nonlinear increase in calcification rate as a function of aragonite saturation level. Porites compressa Manipulation: Acid addition Marubini and Duration: 5 weeks Atkinson, 1999 Design: 760 and 3980 atm (pH = 8.2 versus 7.2); nitrate additions as well Results: Corals grown in low pH water grew half as fast. Porites compressa Manipulation: Acid addition Marubini et al., Duration: 10 weeks 2001 Design: Controlled laboratory experiments: measured calcification at pCO2 = 199 and 448 atm, at 3 light levels. In Biosphere 2 coral mesocosm: measured calcification at pCO2 = 186, 336, and 641 atm. Results: Calcification decreased 30% from pCO2 = 186 to 641, and 11% from pCO2 = 336 to 641 atm, regardless of light level. Galaxeafascicularis Manipulation: Altered Ca2+ ion concentration Marshall and while maintaining pH at 8.118.12; Clode, 2002 temperatures maintained at ambient temperature of collections site1 Duration: Hours Design: Calcium additions to estimated arag from 3.88 (presentday) to 4.83 and 5.77; calcification rate measured with 14C incorporation in skeleton. Results: Calcification rate increased 3060% at arag = 4.83 and 5080% at arag = 5.77 relative to arag =3.88.

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APPENDIXC Organism/ System Summary of findings Reference Stylophora Manipulation: Bubbled CO2 Reynaud et al., pistillata Duration: 5 weeks 2003 Design: 2 pCO2 values (460 and 760 atm) and 2 temperatures (25 and 28C) Results: Calcification under normal temperature did not change in response to an increased pCO2. Calcification decreased by 50% when temperature and pCO2 were both elevated. Acropora verweyi Manipulation: Acid/base addition Marubini et al., Galaxea Duration: 8 days 2003 fascicularis Design: 2 pCO2 values (407416 and Pavona cactus 857882 atm), 26.5C Turbinaria Results: calcification rate in all 4 species reniformis decreased 1318% Poritescompressa+ Manipulation: acid/base addition Langdon and Montiporacapitata Duration: 1.5 hours Atkinson, 2005 Design: Corals placed in flumes, multiple summer experiments at pCO2 = 460 and 789 atm; multiple winter experiments at pCO2 = 391, 526, and 781 atm; additional experiments included additions of PO4 and NH4. Results: Summer calcification rate declined 43% with increase in pCO2 from 460 to 789 atm; winter rates declined 22% from 391 to 526 atm; and 80% from 391 to 781 atm. Acropora Manipulation: Bubbled CO2 Renegar and cericornis Duration: 16 weeks total Riegl, 2005 Design: Nubbins cultured for 1 week at pCO2=367 atm, 2 weeks at 714771 atm, 1 week at 365 atm Results: 6080% reduction in calcification rate at 714771 atm relative to controls (357361 atm); note that calcification rate did not substantially recover with return to normal pCO2 during 4th week.

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APPENDIXC Organism/ System Summary of findings Reference Acroporaeurystoma Manipulation: Acid/base addition Schneider and Duration: Hours Erez, 2006 Design: Separation of effects of different carbonate chemistry parameters by maintaining a) constant total inorganic carbon, b) constant pH, or c) constant CO2; temperatures = 23.524.5C Results: calcification rate was correlated with [CO32]: 50% decrease in calcification with 30% decrease in [CO32]; 35% decrease in calcification with increase in pCO2 from 370 to 560 ppm. Poriteslutea and Manipulation: Acid/base addition Ohde and Fungia sp. Duration: 3 hours (nighttime) and 6 hours Hossain, 2004; (daytime) Hossain and Design: Coral colonies were acclimated for Ohde, 2006 several months, then subjected to seawater adjusted to one of 3 arag levels: 1.56, 3.43, 5.18 (note that ambient arag was 3.43); temperature was constant at 25C. Results: Both day and night calcification decreased with decreasing pH; calcification rate at 2x preindustrial CO2 level (arag = 3.1) was reduced by 42% relative to preindustrial level (arag = 4.6). Montipora Manipulation: Acid addition Jokiel et al., capitata Duration: 10 months 2008 Design: Corals places in flumes: control at ambient reef pCO2 (average 380 ppm), others manipulated to ambient + 365 ppm. Results: Calcification decreased 1520% with a doubling of pCO2 (380 to 380+365 ppm). Poritesastreoides Manipulation: Acid addition Albright et al., (larvae/juveniles) Duration: 2128 days 2008 Design: Flowthrough seawater system; 3 aragonite saturation states: arag = 3.2 (control), 2.6 (mid), and 2.2 (low); constant temperature at 25C Results: Lateral skeletal extension in larvae was positively correlated with saturation state (P=0.007); juveniles in mid arag treatment grew 4556% slower than controls; those in low arag treatments grew 7284% slower than controls.

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APPENDIXC Organism/ System Summary of findings Reference Poriteslobata Manipulation: Bubbled CO2 Anthony et al., Acropora Duration: 8 weeks 2008 intermedia Design: Corals placed in flowthrough aquaria: 2 temperatures: 2526C and 2829C; and 3 pH levels: 8. 08.4 (control) 7.857.95 and 7.607.70. Results: Acropora intermedia and Porites lobata calcification rates were 40% lower at low pH treatment than in control. Faiafragrum Manipulation: Acid addition Cohen et al., (larvae/juveniles) Duration: 8 days 2009 Design: Newly settled coral larvae reared in a range of arag from ambient (3.71) to 3 treatments (arag = 2.40, 1.03, 0.22); culture temperatures =25C. Results: Aragonite was secreted by all corals even in undersaturated conditions; however, in arag = 2.40 treatment, crosssectional area of skeletons was more than 20% less than the control, and average weight of skeletal mass was 26% less than control. Similar trends occurred in the more extreme treatments. Madracismirabilis Manipulation: Acid/base addition and Jury et al., 2009 bubbled CO2 Duration: 2 hour incubations following 3hour acclimation period Design: Separation of effects of different carbonate chemistry parameters by manipulating chemistry to reflect 6 combinations of normal, low and very low pH, with normal low and very low [CO32]; temperature maintained at 28C Results: For pH/[CO32] combinations that simulate natural ocean acidification (pCO2 = 390, 875 and 1400 atm), calcification rate was not correlated with [CO32], but rather with [HCO3].

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APPENDIXC Organism/ System Summary of findings Reference Oculinaarbuscula Manipulation: CO2 bubbling Ries et al., 2009 (temperate coral) Duration: 60 days Design: Controlled laboratory experiment to examine changes in calcification under arag = 3.12, 2.40, 1.84, and 0.90 (approx. pCO2 = 409, 606, 903, 2856 ppmv, respectively). SST maintained at 25C. Results: Calcification rate remained unchanged arag > 1.84, then declined rapidly at arag = 0.90. Lopheliapertussa Manipulation: Acid addition Maier et al., (cold water coral) Duration: 24 hours 2009 Design: Onboard incubations of deep water corals at ambient pH, ambient pH 0.15 units, and ambient pH 0.3 units. Calcification rates measured using 45Ca labeling. Results: Calcification rates were reduced by 30% and 56% at pH reduced by 0.15 and 0.3 units, respectively, as compared to calcification rate at ambient pH. Calcification in young polyps showed a stronger reduction than in old polyps (59% reduction versus 40% reduction, respectively). Carbonate- dominated systems Gr. Bahama Banks Manipulation: NA; field measurements Broecker and Duration: Days Takahashi, 1966; Design: Measured changes in pCO2, DIC, Broecker et al., temperature salinity, and residence time of 2001 Bahama Banks waters. Results: CaCO3 precipitation rate correlated with CaCO3 saturation state. B2 mesocosm Manipulation: Acid/base and CaCl2 Langdon et al., additions and natural alkalinity drawdown 2000; Langdon Duration: Days to months/years (3.8 years et al., 2003 total) Design: Biosphere 2 coral reef mesoscosm; time series of net community calcification measurements in relation to carbonate chemistry. Results: Calcification rate well correlated with saturation state; calcification rate decreased 40% between preindustrial and doubled CO2 conditions.

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0 APPENDIXC Organism/ System Summary of findings Reference Monaco Manipulation: Bubbled CO2 Leclercq et al., mesocosm Duration: 24hour incubations 2000 Design: Coral community mesocosm subjected to continuous flow with a range of pCO2 values (1341813 atm; temperature maintained at 26C Results: Community calcification was reduced by 21% between preindustrial and double pCO2 levels. Monaco Manipulation: Bubbled CO2 Leclercq et al., mesocosm Duration: 930 days 2002 Design: Coral community mesocosm subjected to continuous flow with mid (647 atm) pCO2 for 12 weeks, low (411 atm) for 4 weeks, and high (918 atm) for 4 weeks; temperature maintained at 26C Results: Daytime community calcification was reduced by 12% between low and high treatments. Molokai Reef Manipulation: Natural alkalinity drawdown Yates and System by organisms Halley, 2006 Duration: Several days Design: Large benthic chambers placed on reef bed; in situ carbonate chemistry, salinity, temperature, and net calcification/dissolution measured continuously. Results: Calcification and dissolution were linearly correlated with both CO32 and pCO2. Threshold pCO2 and CO32 values for individual substrate types showed considerable variation. Results indicate that average threshold for shift to net dissolution for Molokai reef is when pCO2 = 654 195 atm.

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APPENDIXC Organism/ System Summary of findings Reference Northern Red Sea Manipulation: NA; field measurements Silverman et al., Reef Duration: 2 years 2007 Design: Eulerian measurements of carbonate system in seawater and community calcification/dissolution rates as a function of saturation state; adjusted for residence time of water. Results: Based on seasonal differences in calcification rate, determine that net reef calcification rate was wellcorrelated with precipitation rates of inorganic aragonite; projected a 55% decrease in reef calcification at 560 ppm CO2 and 30C relative to 280 ppm and 28C Calcifying Manipulation: Acid addition Andersson et community Duration: 24 hours al., 2009 dominated by Design: See Jokiel et al., 2008 and Kuffner Montiporacapitata et al. 2008. Compared Net ecosystem calcification (NEC) in coral community mesosms exposed to ambient pCO2 (380 ppm) and 2x ambient (380+365 ppm). NEC was determined every 2 hours by accounting for changes total alkalinity in the entire system. Results: NEC was 3.3 mmol CaCO3 m2 h1 under ambient and 0.04 mmol CaCO3 m2 h1. 1These studies manipulated Ca2+ rather than the carbon system. They are included here for completeness and because they provide insights into calcification mechanisms, but the results should not be strictly interpreted as a response to ocean acidification.

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