Impact of elevated CO2 on shellfish calcification
TL;DR: In this article, the authors demonstrate that the calcification rates of the edible mussel (Mytilus edulis) and Pacific oyster (Crassostrea gigas) decline linearly with increasing CO2.
Abstract: [1] Ocean acidification resulting from human emissions of carbon dioxide has already lowered and will further lower surface ocean pH. The consequent decrease in calcium carbonate saturation potentially threatens calcareous marine organisms. Here, we demonstrate that the calcification rates of the edible mussel (Mytilus edulis) and Pacific oyster (Crassostrea gigas) decline linearly with increasing pCO2. Mussel and oyster calcification may decrease by 25 and 10%, respectively, by the end of the century, following the IPCC IS92a scenario (∼740 ppmv in 2100). Moreover, mussels dissolve at pCO2 values exceeding a threshold value of ∼1800 ppmv. As these two species are important ecosystem engineers in coastal ecosystems and represent a large part of worldwide aquaculture production, the predicted decrease of calcification in response to ocean acidification will probably have an impact on coastal biodiversity and ecosystem functioning as well as potentially lead to significant economic loss.
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TL;DR: The potential for marine organisms to adapt to increasing CO2 and broader implications for ocean ecosystems are not well known; both are high priorities for future research as mentioned in this paper, and both are only imperfect analogs to current conditions.
Abstract: Rising atmospheric carbon dioxide (CO2), primarily from human fossil fuel combustion, reduces ocean pH and causes wholesale shifts in seawater carbonate chemistry. The process of ocean acidification is well documented in field data, and the rate will accelerate over this century unless future CO2 emissions are curbed dramatically. Acidification alters seawater chemical speciation and biogeochemical cycles of many elements and compounds. One well-known effect is the lowering of calcium carbonate saturation states, which impacts shell-forming marine organisms from plankton to benthic molluscs, echinoderms, and corals. Many calcifying species exhibit reduced calcification and growth rates in laboratory experiments under high-CO2 conditions. Ocean acidification also causes an increase in carbon fixation rates in some photosynthetic organisms (both calcifying and noncalcifying). The potential for marine organisms to adapt to increasing CO2 and broader implications for ocean ecosystems are not well known; both are high priorities for future research. Although ocean pH has varied in the geological past, paleo-events may be only imperfect analogs to current conditions.
2,995 citations
TL;DR: Fabry et al. as discussed by the authors presented new observations, reviewed available data, and identified priorities for future research, based on regions, ecosystems, taxa, and physiological processes believed to be most vulnerable to ocean acidification.
Abstract: Fabry, V. J., Seibel, B. A., Feely, R. A., and Orr, J. C. 2008. Impacts of ocean acidification on marine fauna and ecosystem processes. - ICES Journal of Marine Science, 65: 414-432.Oceanic uptake of anthropogenic carbon dioxide (CO 2 ) is altering the seawater chemistry of the world’s oceans with consequences for marine biota. Elevated partial pressure of CO 2 (pCO 2 ) is causing the calcium carbonate saturation horizon to shoal in many regions, particularly in high latitudes and regions that intersect with pronounced hypoxic zones. The ability of marine animals, most importantly pteropod molluscs, foraminifera, and some benthic invertebrates, to produce calcareous skeletal structures is directly affected by seawater CO 2 chemistry. CO 2 influences the physiology of marine organisms as well through acid-base imbalance and reduced oxygen transport capacity. The few studies at relevant pCO 2 levels impede our ability to predict future impacts on foodweb dynamics and other ecosystem processes. Here we present new observations, review available data, and identify priorities for future research, based on regions, ecosystems, taxa, and physiological processes believed to be most vulnerable to ocean acidification. We conclude that ocean acidification and the synergistic impacts of other anthropogenic stressors provide great potential for widespread changes to marine ecosystems.
1,951 citations
Cites background from "Impact of elevated CO2 on shellfish..."
...( 740 ppmv in 2100), calcification rates in the mussel Mytilus edulis and the Pacific oyster Crassostrea gigas decreased by 25 and 10%, respectively (Gazeau et al., 2007)....
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...In response to an elevated pCO2 level projected to occur under the IS92a emissions scenario ( 740 ppmv in 2100), calcification rates in the mussel Mytilus edulis and the Pacific oyster Crassostrea gigas decreased by 25 and 10%, respectively (Gazeau et al., 2007)....
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TL;DR: The most comprehensive meta-analysis to date by synthesizing the results of 228 studies examining biological responses to ocean acidification reveals decreased survival, calcification, growth, development and abundance in response to acidification, and suggests that other factors, such as nutritional status or source population, could cause substantial variation in organisms' responses.
Abstract: Ocean acidification represents a threat to marine species worldwide, and forecasting the ecological impacts of acidification is a high priority for science, management, and policy. As research on the topic expands at an exponential rate, a comprehensive understanding of the variability in organisms' responses and corresponding levels of certainty is necessary to forecast the ecological effects. Here, we perform the most comprehensive meta-analysis to date by synthesizing the results of 228 studies examining biological responses to ocean acidification. The results reveal decreased survival, calcification, growth, development and abundance in response to acidification when the broad range of marine organisms is pooled together. However, the magnitude of these responses varies among taxonomic groups, suggesting there is some predictable trait-based variation in sensitivity, despite the investigation of approximately 100 new species in recent research. The results also reveal an enhanced sensitivity of mollusk larvae, but suggest that an enhanced sensitivity of early life history stages is not universal across all taxonomic groups. In addition, the variability in species' responses is enhanced when they are exposed to acidification in multi-species assemblages, suggesting that it is important to consider indirect effects and exercise caution when forecasting abundance patterns from single-species laboratory experiments. Furthermore, the results suggest that other factors, such as nutritional status or source population, could cause substantial variation in organisms' responses. Last, the results highlight a trend towards enhanced sensitivity to acidification when taxa are concurrently exposed to elevated seawater temperature.
1,787 citations
TL;DR: The analyses suggest that the biological effects of ocean acidification are generally large and negative, but the variation in sensitivity amongst organisms has important implications for ecosystem responses.
Abstract: Ocean acidification is a pervasive stressor that could affect many marine organisms and cause profound ecological shifts. A variety of biological responses to ocean acidification have been measured across a range of taxa, but this information exists as case studies and has not been synthesized into meaningful comparisons amongst response variables and functional groups. We used meta-analytic techniques to explore the biological responses to ocean acidification, and found negative effects on survival, calcification, growth and reproduction. However, there was significant variation in the sensitivity of marine organisms. Calcifying organisms generally exhibited larger negative responses than noncalcifying organisms across numerous response variables, with the exception of crustaceans, which calcify but were not negatively affected. Calcification responses varied significantly amongst organisms using different mineral forms of calcium carbonate. Organisms using one of the more soluble forms of calcium carbonate (high-magnesium calcite) can be more resilient to ocean acidification than less soluble forms (calcite and aragonite). Additionally, there was variation in the sensitivities of different developmental stages, but this variation was dependent on the taxonomic group. Our analyses suggest that the biological effects of ocean acidification are generally large and negative, but the variation in sensitivity amongst organisms has important implications for ecosystem responses.
1,431 citations
Cites background from "Impact of elevated CO2 on shellfish..."
...…1999; Marubini et al. 2003; Hoegh-Guldberg et al. 2007), planktonic organisms (Riebesell et al. 2000; Orr et al. 2005), bivalves (Michaelidis et al. 2005; Gazeau et al. 2007) and echinoderms (Kurihara & Shirayama 2004; Shirayama & Thornton 2005) amongst others in response to ocean acidification....
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TL;DR: The ocean uptake of anthropogenic CO2 has increased the areal extent of the affected area, and seawater that is undersaturated with respect to aragonite upwelling onto large portions of the continental shelf is observed.
Abstract: The absorption of atmospheric carbon dioxide (CO2) into the ocean lowers the pH of the waters. This so-called ocean acidification could have important consequences for marine ecosystems. To better understand the extent of this ocean acidification in coastal waters, we conducted hydrographic surveys along the continental shelf of western North America from central Canada to northern Mexico. We observed seawater that is undersaturated with respect to aragonite upwelling onto large portions of the continental shelf, reaching depths of approximately 40 to 120 meters along most transect lines and all the way to the surface on one transect off northern California. Although seasonal upwelling of the undersaturated waters onto the shelf is a natural phenomenon in this region, the ocean uptake of anthropogenic CO2 has increased the areal extent of the affected area.
1,336 citations
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TL;DR: 13 models of the ocean–carbon cycle are used to assess calcium carbonate saturation under the IS92a ‘business-as-usual’ scenario for future emissions of anthropogenic carbon dioxide and indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously.
Abstract: Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends continue, key marine organisms—such as corals and some plankton—will have difficulty maintaining their external calcium carbonate skeletons. Here we use 13 models of the ocean–carbon cycle to assess calcium carbonate saturation under the IS92a 'business-as-usual' scenario for future emissions of anthropogenic carbon dioxide. In our projections, Southern Ocean surface waters will begin to become undersaturated with respect to aragonite, a metastable form of calcium carbonate, by the year 2050. By 2100, this undersaturation could extend throughout the entire Southern Ocean and into the subarctic Pacific Ocean. When live pteropods were exposed to our predicted level of undersaturation during a two-day shipboard experiment, their aragonite shells showed notable dissolution. Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously.
4,244 citations
TL;DR: The apparent dissociation constants of carbonic acid in seawater were determined as functions of temperature (2-35°C) and salinity (19-43%) at atmospheric pressure by measurement of K'1 and the product K', K' as discussed by the authors.
Abstract: The apparent dissociation constants of carbonic acid in seawater were determined as functions of temperature (2-35°C) and salinity ( 19-43%) at atmospheric pressure by measurement of K’1 and the product K’, K’,. At 35sa salinity and 25°C the measured values were pE1 = 6.600 and pK’2 = 9.115; at 35% and 2°C the measured values were pK’1 = 6.177 and pKPz = 9.431.
3,085 citations
TL;DR: It is found that oceanic absorption of CO2 from fossil fuels may result in larger pH changes over the next several centuries than any inferred from the geological record of the past 300 million years.
Abstract: The coming centuries may see more ocean acidification than the past 300 million years. Most carbon dioxide released into the atmosphere as a result of the burning of fossil fuels will eventually be absorbed by the ocean1, with potentially adverse consequences for marine biota2,3,4. Here we quantify the changes in ocean pH that may result from this continued release of CO2 and compare these with pH changes estimated from geological and historical records. We find that oceanic absorption of CO2 from fossil fuels may result in larger pH changes over the next several centuries than any inferred from the geological record of the past 300 million years, with the possible exception of those resulting from rare, extreme events such as bolide impacts or catastrophic methane hydrate degassing.
3,060 citations
"Impact of elevated CO2 on shellfish..." refers background in this paper
...Because one third of anthropogenic CO2 emissions has been stored in the oceans, ocean pH has already declined by 0.1 unit compared with preindustrial values [Orr et al., 2005] and is predicted to decrease by another 0.4 unit by the end of the century [ Caldeira and Wickett, 2003 ]....
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...Because one third of anthropogenic CO2 emissions has been stored in the oceans, ocean pH has already declined by 0.1 unit compared with preindustrial values [Orr et al., 2005] and is predicted to decrease by another 0.4 unit by the end of the century [Caldeira and Wickett, 2003]....
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TL;DR: It is suggested that the progressive increase in atmospheric CO2 concentrations may slow down the production of calcium carbonate in the surface ocean, as the process of calcification releases CO2 to the atmosphere.
Abstract: The formation of calcareous skeletons by marine planktonic organisms and their subsequent sinking to depth generates a continuous rain of calcium carbonate to the deep ocean and underlying sediments1 This is important in regulating marine carbon cycling and ocean–atmosphere CO2 exchange2 The present rise in atmospheric CO2 levels3 causes significant changes in surface ocean pH and carbonate chemistry4 Such changes have been shown to slow down calcification in corals and coralline macroalgae5,6, but the majority of marine calcification occurs in planktonic organisms Here we report reduced calcite production at increased CO2 concentrations in monospecific cultures of two dominant marine calcifying phytoplankton species, the coccolithophorids Emiliania huxleyi and Gephyrocapsa oceanica This was accompanied by an increased proportion of malformed coccoliths and incomplete coccospheres Diminished calcification led to a reduction in the ratio of calcite precipitation to organic matter production Similar results were obtained in incubations of natural plankton assemblages from the north Pacific ocean when exposed to experimentally elevated CO2 levels We suggest that the progressive increase in atmospheric CO2 concentrations may therefore slow down the production of calcium carbonate in the surface ocean As the process of calcification releases CO2 to the atmosphere, the response observed here could potentially act as a negative feedback on atmospheric CO2 levels
1,449 citations
"Impact of elevated CO2 on shellfish..." refers background in this paper
...[4] Several experiments have shown a reduction of calcification and size at elevated pCO2 in corals, coralline algae, coccolithophorids and foraminifera [Agegian, 1985; Bijma et al., 1999; Leclercq et al., 2000; Riebesell et al., 2000; Langdon and Atkinson, 2005]....
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