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: 33.61). 05/2008; 320(5874):336-40. DOI: 10.1126/science.1154122
Source: PubMed


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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    • "On the other hand, there are non-calcifying phytoplankton species that benefit from a higher availability of carbon enhancing their growth (Rost et al., 2008; Low-Decarie et al., 2014). Although a direct effect of a lowered pH on phytoplankton (Riebesell et al., 2000a; Kim et al., 2006) and zooplankton (Pedersen and Hansen, 2003; Mayor et al., 2007; Cripps et al., 2014) has been reported for some species, other studies point at only the indirect effects of OA, e.g. by changes in phytoplankton availability, quality, or changes in C : N : P ratios affecting higher levels (Iglesias-Rodriguez et al., 2008; Suffrian et al., 2008; Nielsen and Lewandowska, 2011; Aberle et al., 2012, 2015; Winder et al., 2012; Lewandowska et al., 2014). Here, we present an indoor mesocosm study on the combined effects of enhanced CO 2 and warming on natural autumn plankton communities from Kiel Fjord, characterized by a diatomdominated phytoplankton bloom in autumn (Wasmund et al., 2008). "
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    ABSTRACT: Global warming and ocean acidification are among the most important stressors for aquatic ecosystems in the future. To investigate their direct and indirect effects on a near-natural plankton community, a multiple-stressor approach is needed. Hence, we set up mesocosms in a full-factorial design to study the effects of both warming and high CO 2 on a Baltic Sea autumn plankton community, concentrating on the impacts on micro-zooplankton (MZP). MZP abundance, biomass, and species composition were analysed over the course of the experiment. We observed that warming led to a reduced time-lag between the phytoplankton bloom and an MZP biomass maximum. MZP showed a significantly higher growth rate and an earlier biomass peak in the warm treatments while the biomass maximum was not affected. Increased pCO 2 did not result in any significant effects on MZP biomass, growth rate, or species composition irrespective of the temperature, nor did we observe any significant interactions between CO 2 and temperature. We attribute this to the high tolerance of this estuarine plankton community to fluctuations in pCO 2 , often resulting in CO 2 concentrations higher than the predicted end-of-century concentration for open oceans. In contrast, warming can be expected to directly affect MZP and strengthen its coupling with phytoplankton by enhancing its grazing pressure.
    ICES Journal of Marine Science 11/2015; DOI:10.1093/icesjms/fsv198 · 2.38 Impact Factor
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    • "(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) coccolithophore Emiliania huxleyi, which can use the additional available CO 2 for photosynthesis under certain conditions (Iglesias-Rodriguez et al., 2008), diatoms or seagrass which were shown to increase under high pCO 2 (Johnson et al., 2011). Such variability in the response of organisms to ocean acidification makes it difficult to predict the overall effects of ocean acidification at the ecosystem level. "
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    ABSTRACT: Shallow CO2 seeps, where CO2 gas is venting underwater, offer great potential for studies into the effects of ocean acidification at the ecosystem level. To our knowledge, only two tropical system and two temperate systems of such seeps have been described worldwide. Here we describe two new temperate systems: the Mikama Bay and Ashitsuke sites, located on Shikine Island, Japan. The Mikama Bay site is located in a shallow bay. Investigation of the gas and water chemistry showed that the gas contained 98% CO2 and up to 90 ppm H2S. Total alkalinity was constant in time and space with an average of 2265±10 μ mol kg−1. Mapping of Eh and pH showed that the low pH zones were the largest when currents were moderate. Under moderate currents, Eh values were globally higher and total sulfides concentration lower, supporting that a longer residence time of the bay water allow the oxidation of the sulfides to sulfates. Zones suitable for acidification studies: with a pH lower than 8.0, low saturation state of calcite and aragonite, and non-detectable sulfide concentration, can be defined a few meters from the main venting zone. The second site, Ashitsuke, is located in the inter-tidal zone on a shore composed of boulders. Several areas showed reduced pH sometimes restricted to a few meters and up to 20 m long along the shoreline. Temperature was higher in some of the reduced pH zones suggesting the presence of hot springs in addition to vents. This paper also highlights the need for discovering additional CO2 seeps, which by their nature often lack comparable replicates and can be confounded by factors other than CO2. In this regard, Japan offers great potential as it is home to numerous active volcanoes, representing potential venting sites in climates ranging from tropical to sub-polar.
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    • "However, as CO 2 increases and ocean pH decreases, high-latitude regions (e.g., the Southern Ocean) are predicted to become undersaturated in calcite by the year 2100 (Orr et al., 2005), which could result in the dissolution of coccoliths , potentially impacting the competitiveness of this group. Many studies show that photosynthetic rates of coccolithophores are not saturated at ambient CO 2 (Figure 2A; Zondervan et al., 2001, 2002; Langer et al., 2006, 2009; Iglesias-Rodriguez et al., 2008; Shi et al., 2009; De Bodt et al., 2010; Ramos et al., 2010; Fiorini et al., 2011b; Langer, 2011; Richier et al., 2011; Lefebvre et al., 2012; Müller et al., 2012; Rokitta and Rost, 2012), and some studies also show increases in calcification and net growth rate at elevated CO 2 , at least in certain environmental conditions (Feng et al., 2008; Iglesias-Rodriguez et al., 2008; Zondervan et al., 2002; Shi et al., 2009; De Bodt et al., 2010; Fiorini et al., 2011a,b; Lefebvre et al., 2012; Spielmeyer and Pohnert, 2012). Light harvesting efficiency (the α-parameter of the PE curve) tends to increase with elevated CO 2 , whereas saturating irradiance (E k ) decreases, suggesting that elevated CO 2 improves photosynthetic rates for these organisms at low irradiances (Feng et al., 2008; Rokitta and Rost, 2008, 2012). "
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    ABSTRACT: All phytoplankton and higher plants perform photosynthesis, where carbon dioxide is incorporated into biomass during cell growth. Ocean acidification (OA) has the potential to affect photosynthetic kinetics due to increasing seawater pCO2 levels and lower pH. The effects of increased CO2 are difficult to predict because some species utilize carbon concentrating mechanisms that buffer their sensitivity to ambient CO2 levels and require variable energy investments. Here, we discuss the current state of knowledge about the effects of increased CO2 on photosynthesis across marine photosynthetic taxa from cyanobacteria and single-celled eukaryotes to marine macrophytes. The analysis shows that photosynthetic responses to OA are relatively small for most investigated species and highly variable throughout taxa. This could suggest that the photosynthetic benefits of high CO2 are minor relative to the cell’s overall energy and material balances, or that the benefit to photosynthesis is counteracted by other negative effects, such as possible respiratory costs from low pH. We conclude with recommendations for future research directions, such as probing how other physiological processes respond to OA, the effects of multiple stressors, and the potential evolutionary outcomes of longterm growth under ocean acidification.
    Oceanography (Washington D.C.) 06/2015; 25(2):74-91. DOI:10.5670/oceanog.2015.33 · 2.94 Impact Factor
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