Article

Phytoplankton Calcification in a High-CO2 World

National Oceanography Centre, Southampton, University of Southampton Waterfront Campus, European Way, Southampton SO14 3ZH, UK.
Science (Impact Factor: 31.48). 05/2008; 320(5874):336-40. DOI: 10.1126/science.1154122
Source: PubMed

ABSTRACT Ocean acidification in response to rising atmospheric CO2 partial pressures is widely expected to reduce calcification by marine organisms. From the mid-Mesozoic, coccolithophores
have been major calcium carbonate producers in the world's oceans, today accounting for about a third of the total marine
CaCO3 production. Here, we present laboratory evidence that calcification and net primary production in the coccolithophore species
Emiliania huxleyi are significantly increased by high CO2 partial pressures. Field evidence from the deep ocean is consistent with these laboratory conclusions, indicating that over
the past 220 years there has been a 40% increase in average coccolith mass. Our findings show that coccolithophores are already
responding and will probably continue to respond to rising atmospheric CO2 partial pressures, which has important implications for biogeochemical modeling of future oceans and climate.

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Available from: Eric Rehm, Jul 27, 2015
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    • "Atmospheric CO 2 concentration could rise as high as 1000 ppmv by the end of this century (IPCC, 2007) driving ocean acidification, i.e. raising the partial pressure of CO 2 (pCO 2 ) and lowering the pH and carbonate ion concentration [CO 3 2– ] in seawater (Caldeira and Wickett, 2003; Feely et al., 2008). The projected increase in seawater pCO 2 may have critical negative impacts on both calcification (Gattuso and Buddemeier, 2000; Iglesias-Rodriguez et al., 2008; Riebesell et al., 2007) and a range of physiological processes across numerous marine invertebrate taxa (Albright et al., 2010; Byrne et al., 2010a,b; Dupont et al., 2010a,b; Ericson et al., 2010; Harley et al., 2006; Havenhand et al., 2008; Kim et al., 2013; Kroeker et al., 2010; Kurihara et al., 2008; Orr et al., 2005; Parker et al., 2010; Raven et al., 2005; Reuter et al., 2011; Sheppard Brennand et al., 2010; Widdicombe and Spicer, 2008). When assessing the impact of increased seawater pCO 2 on marine invertebrate populations, it is critical to focus initial studies on processes occurring within the earliest life stages, such as fertilization , embryogenesis, and larval development, during which invertebrates are typically most sensitive to environmental factors (Brierley and Kingsford, 2009; Byrne et al., 2011; Cowen et al., 2000; Harley et al., 2006; Havenhand and Schlegel, 2009; Havenhand et al., 2008; Pechenik, 1999; Przeslawski et al., 2008; Raven et al., 2005; Thorsong, 1950; Uthicke et al., 2009; Ross et al. 2011). "
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    ABSTRACT: Since the Industrial Revolution, rising atmospheric CO2 concentration has driven an increase in the partial pressure of CO2 in seawater (pCO2), thus lowering ocean pH. We examined the separate effects of exposure of gametes to elevated pCO2 and low pH on fertilization success of the sea urchin Strongylocentrotus nudus. Sperm and eggs were independently exposed to seawater with pCO2 levels ranging from 380 (pH 7.96 – 8.3) to 6000 ppmv (pH 7.15 – 7.20). When sperm were exposed, fertilization rate decreased drastically with increased pCO2, even at a concentration of 450 ppmv (pH range: 7.94 to 7.96). Conversely, fertilization of H. pulcherrimus was not significantly changed even when sperm was exposed to pCO2 concentrations as high as 750 ppmv. Exposure of S. nudus eggs to seawater with high pCO2 did not affect fertilization success, suggesting the effect of increased pCO2 on sperm is responsible for reduced fertilization success. Surprisingly, this result was not related to sperm motility, which was insensitive to pCO2. When seawater was acidified using HCl, leaving pCO2 constant, fertilization success in S. nudus remained high (> 80%) until pH decreased to 7.3. While further studies are required to elucidate the physiological mechanism by which elevated pCO2 impairs sperm and reduces S. nudus fertilization, this study suggests that in the foreseeable future, sea urchin survival may be threatened due to lower fertilization success driven by elevated pCO2 rather than by decreased pH in seawater.
    Journal of Marine Systems 09/2014; 137. DOI:10.1016/j.jmarsys.2014.04.013 · 2.48 Impact Factor
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    • "Photosynthetic performance in crustose corallines has previously been shown to be negatively affected by high levels of pCO 2 (Anthony et al., 2008; Gao and Zheng, 2010; Martin et al., 2013). However, increases in pCO 2 may also enhance productivity in some marine algae by alleviating carbon limitation, particularly when pCO 2 levels are below 1000 ppm (Bowes, 1993; Iglesias-Rodriguez et al., 2008), and this has been observed in coralline algae grown under high pCO 2 conditions (Ries et al., 2009; Semesi et al., 2009). Our results indicated no effect of higher pCO 2 alone on the measured photosynthetic parameters. "
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    ABSTRACT: Ocean acidification is a decrease in seawater pH and carbonate ion concentration due to increased uptake of atmospheric carbon dioxide by the world's oceans. This has major implications for many marine organisms, particularly the calcifiers. Crustose coralline algae (CCA) are among the most sensitive calcifying organisms to ocean acidification. In contrast, filamentous turf algae, which compete with CCA for space on the substratum, could potentially benefit from high pCO2 conditions, suggesting that the effects of filamentous turf on coralline algae may be amplified in a high pCO2 environment. The effect of ocean acidification on the growth of coralline algae, however, has rarely been investigated in combination with ecological interactions such as competition with filamentous turfing algae. Here we tested the combined effects of ocean acidification and overgrowth by filamentous turf algae on CCA calcification, photosynthetic capacity and quantum yield of photosynthesis. We observed a positive effect of algal turfs on CCA calcification but a negative effect on photosynthesis in the high pCO2 treatments, however, these effects were variable over time. Our results have demonstrated the importance of investigating how inter-species interactions such as competition will complicate the impacts of ocean acidification.
    Journal of Experimental Marine Biology and Ecology 07/2014; 456:70–77. DOI:10.1016/j.jembe.2014.03.014 · 2.48 Impact Factor
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    • "The relationship between E. huxleyi coccolith dissolution/calcification is non-linear and complicated not least by its extensive morpho/genotypic variability . Recent culture experiments suggest that some strains of E. huxleyi could withstand changes in pH much better than others (Iglesias-Rodriguez et al., 2008; Langer et al., 2009). Why this is so is unclear, but one possibility is that photosynthesis in E. huxleyi is more efficient at higher levels of CO 2 . "
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    ABSTRACT: Coccolithophores are one of the most abundant eukaryotic phytoplankton in the oceans and are distinguished by their ability to build calcitic platelets (coccoliths). Of the numerous species, Emiliania huxleyi is considered one of the major calcifiers in the pelagic ocean. There is growing concern that increasing levels of CO2 in the atmos- phere and the subsequent acidification of the ocean may disrupt the production of coccoliths. Furthermore, any change in the global distribution and abundance of E. huxleyi relative to non-calcifying groups of phytoplankton (e.g. diatoms) will have important effects on the biogeochemical cycling of carbon and climatic feedbacks. We review different lines of evidence that suggest E. huxleyi is increasingly expanding its range into the polar oceans. These observations contribute to the debate on the climatic effects on natural coccolithophore populations. We postulate that E. huxleyi may be more sensitive to recent environmental changes such as increasing sea surface temperature and salinity than to changing ocean carbonate chemistry, partly because increased availability of CO2(aq) likely alleviates a carbon limitation for the inefficient Rubisco enzyme in these algae. Any potentially important climatic feed- backs of coccolithophores need a better knowledge of the mechanisms and rates of adaptation by natural populations. As more data and modelling work become available, the real significance of this poleward expansion will become clear.
    Journal of Plankton Research 03/2014; 36(2):316-325. DOI:10.1093/plankt/fbt110 · 2.26 Impact Factor
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