Marine and Freshwater Acidification: Effects on Multiple Species
From ClimateWiki
Two additional papers have examined the potential effects of ocean acidification and furthered our understanding of this phenomenon. The first, by Ries et al. (2009), explored the effects of lowering seawater pH on 18 oceanic species. The second study, by Hendriks et al. (2010), presented an ocean acidification meta-analysis in which the researchers calculated such effects on dozens of marine species.
Acknowledging “there is mounting concern over the impact that future CO2-induced reductions in the CaCO3 saturation state of seawater will have on marine organisms that construct their shells and skeletons from this mineral,” Ries et al. (2009) set out to conduct an experiment in which they “reared 18 calcifying species for 60 days in isothermal (25°C) experimental seawaters equilibrated with average [atmospheric] CO2 values of 409, 606, 903 and 2856 ppm, corresponding to modern CO2, and ~2, 3 and 10 times pre-industrial levels (~280 ppm), respectively, and yielding average seawater saturation states of 2.5, 2.0, 1.5 and 0.7 with respect to aragonite.” Then, “the organisms’ net rates of calcification (total calcification minus total dissolution) under the various CO2 treatments were estimated from changes in their buoyant weight and verified with dry weight measurements after harvesting.”
According to the three Woods Hole Oceanographic Institution (USA) researchers, their study showed “in ten of the 18 species (temperate corals, pencil urchins, hard clams, conchs, serpulid worms, periwinkles, bay scallops, oysters, whelks, soft clams), net calcification decreased with increasing CO2,” and “in six of the ten negatively impacted species (pencil urchins, hard clams, conchs, periwinkles, whelks, soft clams) [they] observed net dissolution of the shell in the highest CO2 treatment.” However, as they continue, “in four of the 18 species (limpets, purple urchins, coralline red algae, calcareous green algae), net calcification increased relative to the control under intermediate CO2 levels (605 and 903 ppm), and then declined at the highest CO2 level (2856 ppm).” Last, they state “in three species (crabs, lobsters, and shrimps), net calcification was greatest under the highest level of CO2 (2856 ppm),” and “one species, the blue mussel, exhibited no response to elevated CO2.”
In light of their many, diverse findings, Ries et al. concluded “the impact of elevated atmospheric CO2 on marine calcification is more varied than previously thought,” and so it is, with the reported responses ranging from negative to neutral to positive.
In another multiple-species study, Hendriks et al. (2010) assembled a database of 372 experimentally evaluated responses of 44 different marine species to ocean acidification that was induced by equilibrating seawater with CO2-enriched air. At the time, this study represented the most comprehensive analysis ever conducted on this issue.
Of the 372 published reports they scrutinized, 154 assessed the significance of responses relative to controls; and of those reports, 47 reported no significant response, so “only a minority of studies,” in their words, demonstrated “significant responses to acidification.” And when the results of that minority group of studies were pooled, there was no significant mean effect. Nevertheless, the three researchers found some types of organisms and certain functional processes did exhibit significant responses to seawater acidification. However, since their analyses to this point had included some acidification treatments that were extremely high, they repeated their analyses for only those acidification conditions induced by atmospheric CO2 concentrations of 2,000 ppm or less, the latter limiting concentration having been predicted to occur around the year 2300 by Caldeira and Wickett (2003).
In this second analysis, Hendriks et al. once again found the overall response, including all biological processes and functional groups, was not significantly different from that of the various control treatments, although calcification was reduced by 33 ± 4.5 percent and fertility by 11 ± 3.5 percent across groups, while survival and growth showed no significant overall responses. And when the upper limiting CO2 concentrations were in the range of 731–759 ppm, or just below the value predicted by the IPCC (2007) for the end of the twenty-first century (790 ppm)—calcification rate reductions of only 25 percent were observed. What is more, the three researchers state this decline “is likely to be an upper limit, considering that all experiments involve the abrupt exposure of organisms to elevated pCO2 values, while the gradual increase in pCO2 that is occurring in nature may allow adaptive and selective processes to operate,” citing the work of Widdicombe et al. (2008) and noting “these gradual changes take place on the scale of decades, permitting adaptation of organisms even including genetic selection.”
Indeed, there is a large and accumulating volume of research that demonstrates rapid micro-evolutionary processes operate in almost all of Earth’s life forms, and these phenomena enable them to successfully cope with significant environmental changes at rates that correspond to those environmental changes (Balanya et al., 2006; Jump et al., 2006; Franks et al., 2007; Rae et al., 2007; Skelly et al., 2007; Van Doorslaer et al., 2007; Franks and Weis, 2008; Jump et al., 2008; Purcell et al., 2008; Alford et al., 2009; Bell and Gonzalez, 2009; Onoda et al., 2009; Van Doorslaer et al., 2009). Thus, species that respond negatively to dramatic step increases in the air’s CO2 content employed in many of the experiments analyzed by Hendriks et al. will likely be able to gradually adjust to, and successfully cope with, the restrained and slower rate at which the atmospheric CO2 concentration of the real world will rise in the future.
Yet even this mitigating factor is not the end of the good news, for Hendriks et al. write “most experiments assessed organisms in isolation, rather than [within] whole communities,” and they state the responses of other entities and processes within the community may well buffer the negative impacts of CO2-indced acidification on Earth’s corals. As an example, they note “sea-grass photosynthetic rates may increase by 50 percent with increased CO2, which may deplete the CO2 pool, maintaining an elevated pH that may protect associated calcifying organisms from the impacts of ocean acidification.”
In describing another phenomenon that benefits corals, the researchers write, “seasonal changes in pCO2 are in the range of 236–517 ppm in the waters of the northern East China Sea (Shim et al., 2007),” and “metabolically-active coastal ecosystems experience broad diel changes in pH, such as the diel changes of >0.5 pH units reported for sea grass ecosystems (Invers et al., 1997),” which they say represent “a broader range than that expected to result from ocean acidification expected during the 21st century.” They remark these fluctuations also “offer opportunities for adaptation to the organisms involved.”
Hendriks et al. additionally state the models upon which the ocean acidification threat is based “focus on bulk water chemistry and fall short of addressing conditions actually experienced by [marine] organisms,” which are “separated from the bulk water phase by a diffusive boundary layer.” They also note “photosynthetic activity”—such as that of the zooxanthellae that are hosted by corals—“depletes pCO2 and raises pH (Kuhl et al., 1995) so the pH actually experienced by organisms may differ greatly from that in the bulk water phase (Sand-Jensen et al., 1985).”
The insightful scientists then note “calcification is an active process where biota can regulate intracellular calcium concentrations,” so that “marine organisms, like calcifying coccolithophores (Brownlee and Taylor, 2004), actively expel Ca2+ through the ATPase pump to maintain low intracellular calcium concentrations (Corstjens et al., 2001; Yates and Robbins, 1999).” And they state, “as one Ca2+ is pumped out of the cell in exchange for 2H+ pumped into the cell, the resulting pH and Ca2+ concentrations increase the CaCO3 saturation state near extracellular membranes and appear to enhance calcification (Pomar and Hallock, 2008),” so much so, in fact, that they indicate “there is evidence that calcification could even increase in acidified seawater, contradicting the traditional belief that calcification is a critical process impacted by ocean acidification (Findlay et al., 2009).”
Hendriks et al. conclude the world’s marine biota are “more resistant to ocean acidification than suggested by pessimistic predictions identifying ocean acidification as a major threat to marine biodiversity,” noting this phenomenon “may not be the widespread problem conjured into the 21st century” by the IPCC. And in one final parting blow to the theory, Hendriks et al. state, “biological processes can provide homeostasis against changes in pH in bulk waters of the range predicted during the 21st century.”
References
Alford, R.A., Brown, G.P., Schwarzkopf, L, Phillips, B.L., and Shine, R. 2009. Comparisons through time and space suggest rapid evolution of dispersal behaviour in an invasive species. Wildlife Research 36: 23–28.
Balanya, J., Oller, J.M., Huey, R.B., Gilchrist, G.W., and Serra, L. 2006. Global genetic change tracks global climate warming in Drosophila subobscura. Science 313: 1773–1775.
Bell, G. and Gonzalez, A. 2009. Evolutionary rescue can prevent extinction following environmental change. Ecology Letters 12: 942–948.
Brownlee, C. and Taylor, A. 2004. Calcification in coccolithophores: a cellular perspective. In Coccolithophores, edited by H.R. Thierstein and J.R. Young, 31–49. Berlin, Germany: Springer.
Caldeira, K. and Wickett, M.E. 2003. Anthropogenic carbon and ocean pH. Nature 425: 365.
Corstjens, P.L.A.M., Araki, Y., and Gonzalez, E.L. 2001. A coccolithophorid calcifying vesicle with a vacuolar-type ATPase proton pump: cloning and immunolocalization of the V0 subunit c. Journal of Phycology 37: 71–78.
Findlay, H.S., Wood, H.L., Kendall, M.A., Spicer, J.I., Twitchett, R.J., and Widdicombe, S. 2009. Calcification, a physiological process to be considered in the context of the whole organism. Biogeosciences Discussions 6: 2267–2284.
Franks, S.J., Sim, S., and Weis, A.E. 2007. Rapid evolution of flowering time by an annual plant in response to a climate fluctuation. Proceedings of the National Academy of Sciences USA 104: 1278–1282.
Franks, S.J. and Weis, A.E. 2008. A change in climate causes rapid evolution of multiple life-history traits and their interactions in an annual plant. Journal of Evolutionary Biology 21: 1321–1334.
Hendriks, I.E., Duarte, C.M., and Alvarez, M. 2010. Vulnerability of marine biodiversity to ocean acidification: A meta-analysis. Estuarine, Coastal and Shelf Science 86: 157–164.
Invers, O., Romero, J., and Perez, M. 1997. Effects of pH on seagrass photosynthesis: a laboratory and field assessment. Aquatic Botany 59: 185–194. IPCC. 2007. Climate Change 2007: Synthesis Report.
Jump, A.S., Hunt, J.M., Martinez-Izquierdo, J.A., and Penuelas, J. 2006. Natural selection and climate change: temperature-linked spatial and temporal trends in gene frequency in Fagus sylvatica. Molecular Ecology 15: 3469–3480.
Jump, A.S., Penuelas, J., Rico, L., Ramallo, E., Estiarte, M., Martinez-Izquierdo, J.A., and Lloret, F. 2008. Simulated climate change provokes rapid genetic change in the Mediterranean shrub Fumana thymifolia. Global Change Biology 14: 637–643.
Kuhl, M., Cohen, Y., Dalsgaard, T., and Jorgensen, B.B. 1995. Microenvironment and photosynthesis of zooxanthellae in scleractinian corals studied with microsensors for O2, pH and light. Marine Ecology Progress Series 117: 159–172.
Onoda, Y., Hirose, T., and Hikosaka, K. 2009. Does leaf photosynthesis adapt to CO2-enriched environments? An experiment on plants originating from three natural CO2 springs. New Phytologist 182: 698–709.
Pomar, L. and Hallock, P. 2008. Carbonate factories: a conundrum in sedimentary geology. Earth-Science Reviews 87: 134–169.
Purcell, K.M., Hitch, A.T., Klerks, P.L., and Leberg, P.L. 2008. Adaptation as a potential response to sea-level rise: a genetic basis for salinity tolerance in populations of a coastal marsh fish. Evolutionary Applications 1: 155–160.
Rae, A.M., Tricker, P.J., Bunn, S.M., and Taylor, G. 2007. Adaptation of tree growth to elevated CO2: quantitative trait loci for biomass in Populus. New Phytologist 175: 59–69.
Ries, J.B., Cohen, A.L., and McCorkle, D.C. 2009. Marine calcifiers exhibit mixed responses to CO2-induced ocean acidification. Geology 37: 1131–1134.
Sand-Jensen, K., Revsbech, N.P., and Barker Jorgensen, B.B. 1985. Microprofiles of oxygen in epiphyte communities on submerged macrophytes. Marine Biology 89: 55–62.
Shim, J.H., Kim, D., Kang, Y.C., Lee, J.H., Jang, S.T., and Kim, C.H. 2007. Seasonal variations in pCO2 and its controlling factors in surface seawater of the northern East China Sea. Continental Shelf Research 27: 2623–2636.
Skelly, D.K., Joseph, L.N., Possingham, H.P., Freidenburg, L.K., Farrugia, T.J., Kinnison, M.T., and Hendry, A.P. 2007. Evolutionary responses to climate change. Conservation Biology 21: 1353–1355.
Van Doorslaer, W., Stoks, R., Duvivier, C., Bednarska, A., and De Meester, L. 2009. Population dynamics determine genetic adaptation to temperature in Daphnia. Evolution 63: 1867–1878.
Van Doorslaer, W., Stoks, R., Jeppesen, E., and De Meester, L. 2007. Adaptive microevolutionary responses to simulated global warming in Simocephalus vetulus: a mesocosm study. Global Change Biology 13: 878–886.
Widdicombe, S., Dupont, S., and Thorndyke, M. 2008. Laboratory Experiments and Benthic Mesocosm Studies. Guide for Best Practices in Ocean Acidification Research and Data Reporting. Nice, France: European Project on Ocean Acidification (EPOCA).
Yates, K.K. and Robbins, L.L. 1999. Radioisotope tracer studies of inorganic carbon and Ca in microbially derived CaCO3. Geochimica et Cosmochimica Acta 63: 129–136.
