Emiliania Huxleyi Strain Research Articles

Targeted and untargeted lipidomic analysis of haptophyte cultures reveals novel and divergent nutrient-stress adaptations

Lipids comprise a significant, highly plastic proportion of the biomass in haptophytes, a ubiquitous, globally significant, and genetically diverse clade of photosynthetic microalgae. Recent studies have investigated the cellular lipidomes of disparate, individual species of haptophytes under nutrient-replete and nutrient-limited conditions, but have not investigated how lipidomes vary across the larger evolutionary clade or its ecological functional groups. We cultured eight species of haptophytes, including five strains of Emiliania huxleyi, for analysis via high performance liquid chromatography–high resolution accurate mass–mass spectrometry (HPLC–HRAM–MS), and performed untargeted computational and hierarchical cluster analyses on their lipidomes. We identified similarities and differences in lipidomes along both evolutionary and ecological lines, and identified potential biomarkers for haptophyte sub-clades, including 38 glycosphingolipids, seven betaine-like lipids, and three phosphatidyl-S,S-dimethylpropanethiol (PDPT) sulfo-phospholipids. We also provide the first evidence for the glycolipid, glucuronosyldiacylglycerol, in eukaryotic microalgae. We conducted a more targeted study of four haptophyte species under nitrogen- and phosphorus-limited conditions to investigate their lipidomic responses to nutrient stress. Under N- and P-limitation, the species exhibited disparate lipidomic responses. Uniquely, in response to N-limitation, E. huxleyi CCMP 374 heavily upregulated PDPT from 3.6 ± 0.9% to 10.4 ± 1.5% of quantified polar lipids. These previously uncharacterized lipidomes and responses to nutrient limitation reflect divergent evolutionary strategies and challenge popular phenotypic extrapolations between species.

Relationship between coccolith length and thickness in the coccolithophore species Emiliania huxleyi and Gephyrocapsa oceanica.

Coccolith mass is an important parameter for estimating coccolithophore contribution to carbonate sedimentation, organic carbon ballasting and coccolithophore calcification. Single coccolith mass is often estimated based on the ks model, which assumes that length and thickness increase proportionally. To evaluate this assumption, this study compared coccolith length, thickness, and mass of seven Emiliania huxleyi strains and one Gephyrocapsa oceanica strain grown in 25, 34, and 44 salinity artificial seawater. While coccolith length increased with salinity in four E. huxleyi strains, thickness did not increase significantly with salinity in three of these strains. Only G. oceanica showed a consistent increase in length with salinity that was accompanied by an increase in thickness. Coccolith length and thickness was also not correlated in 14 of 24 individual experiments, and in the experiments in which there was a positive relationship r2 was low (<0.4). Because thickness did not increase with length in E. huxleyi, the increase in mass was less than expected from the ks model, and thus, mass can not be accurately estimated from coccolith length alone.

Hydrogen isotope fractionation response to salinity and alkalinity in a calcifying strain of Emiliania huxleyi

Hydrogen isotope ratios of long-chain alkenones (δ2HC37) correlate with water isotope ratios and salinity, albeit with varying degrees of biological fractionation between alkenones and water. These differences in fractionation are the result of environmental and species related effects, which in some cases have consequences for the magnitude of the δ2HC37 response per unit increase in salinity. Earlier culture experiments have focused on constraining hydrogen isotope fractionation factor α in non-calcifying strains of Emiliania huxleyi. Here we studied isotopic fractionation in a calcifying strain of E. huxleyi and show that although absolute fractionation is different, the response to changes in salinity and alkalinity is similar to those of non-calcifying species. This suggests that calcification does not alter the δ2HC37 response to salinity significantly.

Temperature effects on sinking velocity of different Emiliania huxleyi strains.

The sinking properties of three strains of Emiliania huxleyi in response to temperature changes were examined. We used a recently proposed approach to calculate sinking velocities from coccosphere architecture, which has the advantage to be applicable not only to culture samples, but also to field samples including fossil material. Our data show that temperature in the sub-optimal range impacts sinking velocity of E. huxleyi. This response is widespread among strains isolated in different locations and moreover comparatively predictable, as indicated by the similar slopes of the linear regressions. Sinking velocity was positively correlated to temperature as well as individual cell PIC/POC over the sub-optimum to optimum temperature range in all strains. In the context of climate change our data point to an important influence of global warming on sinking velocities. It has recently been shown that seawater acidification has no effect on sinking velocity of a Mediterranean E. huxleyi strain, while nutrient limitation seems to have a small negative effect on sinking velocity. Given that warming, acidification, and lowered nutrient availability will occur simultaneously under climate change scenarios, the question is what the net effect of different influential factors will be. For example, will the effects of warming and nutrient limitation cancel? This question cannot be answered conclusively but analyses of field samples in addition to laboratory culture studies will improve predictions because in field samples multi-factor influences and even evolutionary changes are not excluded. As mentioned above, the approach of determining sinking rate followed here is applicable to field samples. Future studies could use it to analyse not only seasonal and geographic patterns but also changes in sinking velocity over geological time scales.

Environmental controls on the elemental composition of a Southern Hemisphere strain of the coccolithophore &amp;lt;i&amp;gt;Emiliania huxleyi&amp;lt;/i&amp;gt;

Abstract. A series of semi-continuous incubation experiments were conducted with the coccolithophore Emiliania huxleyi strain NIWA1108 (Southern Ocean isolate) to examine the effects of five environmental drivers (nitrate and phosphate concentrations, irradiance, temperature, and partial pressure of CO2 (pCO2)) on both the physiological rates and elemental composition of the coccolithophore. Here, we report the alteration of the elemental composition of E. huxleyi in response to the changes in these environmental drivers. A series of dose–response curves for the cellular elemental composition of E. huxleyi were fitted for each of the five drivers across an environmentally representative gradient. The importance of each driver in regulating the elemental composition of E. huxleyi was ranked using a semi-quantitative approach. The percentage variations in elemental composition arising from the change in each driver between present-day and model-projected conditions for the year 2100 were calculated. Temperature was the most important driver controlling both cellular particulate organic and inorganic carbon content, whereas nutrient concentrations were the most important regulator of cellular particulate nitrogen and phosphorus of E. huxleyi. In contrast, elevated pCO2 had the greatest influence on cellular particulate inorganic carbon to organic carbon ratio, resulting in a decrease in the ratio. Our results indicate that the different environmental drivers play specific roles in regulating the elemental composition of E. huxleyi with wide-reaching implications for coccolithophore-related marine biogeochemical cycles, as a consequence of the regulation of E. huxleyi physiological processes.

Direct measurement of multi-elements in high matrix samples with a flow injection ICP-MS: application to the extended Emiliania huxleyi Redfield ratio.

The quotas of a limited number of trace elements in the extended Redfield ratios have been determined before and thought to reflect the requirements of phytoplankton. However, these quotas are found to be quite variable under different environmental conditions, suggesting that the cellular trace metal quota is not an accurate measure of cellular trace metal requirement. Here we present a method that has been developed and optimised for direct analysis of 32 elements simultaneously in small volume of cell lysate in buffers with a high salt matrix (800 μL, up to 30% TDS). We then demonstrate the application of the method to resolve the extended Redfield ratio of cell requirement by measuring the intracellular trace element composition of six Emiliania huxleyi strains isolated from different locations. The method uses a quadrupole-ICP-MS with a collision/reaction cell to resolve polyatomic interferences. The ICP-MS is interfaced with an Elemental Scientific Flow Injection Automation System (FIAS). The accuracy of the analysis according to this new method is verified by measuring 2 certified reference materials, BCR 273 and BCR 414. This work presents a number of running parameters, optimised for multi-element analysis of samples with a high TDS sample matrix. This method allows direct measurement of protein samples in their native state: no alteration or digestion is needed, which simplifies the steps for sample preparation. In this study with 6 E. huxleyi strains isolated from the environment, our method reveals significant differences between whole cell and intracellular metal quotas for all strains. The intracellular metal composition, interpreted as a truer representation of organisms' metal requirements, shows an environmentally dependent signal. This suggests that, compared with whole cell metal quotas, the metalloproteins are a better indicator of metal requirements of phytoplankton under various environmental conditions.

Physiological responses of coccolithophores to abrupt exposure of naturally low pH deep seawater.

Upwelling is the process by which deep, cold, relatively high-CO2, nutrient-rich seawater rises to the sunlit surface of the ocean. This seasonal process has fueled geoengineering initiatives to fertilize the surface ocean with deep seawater to enhance productivity and thus promote the drawdown of CO2. Coccolithophores, which inhabit many upwelling regions naturally ‘fertilized’ by deep seawater, have been investigated in the laboratory in the context of ocean acidification to determine the extent to which nutrients and CO2 impact their physiology, but few data exist in the field except from mesocosms. Here, we used the Porcupine Abyssal Plain (north Atlantic Ocean) Observatory to retrieve seawater from depths with elevated CO2 and nutrients, mimicking geoengineering approaches. We tested the effects of abrupt natural deep seawater fertilization on the physiology and biogeochemistry of two strains of Emiliania huxleyi of known physiology. None of the strains tested underwent cell divisions when incubated in waters obtained from <1,000 m (pH = 7.99–8.08; CO2 = 373–485 p.p.m; 1.5–12 μM nitrate). However, growth was promoted in both strains when cells were incubated in seawater from ~1,000 m (pH = 7.9; CO2 ~560 p.p.m.; 14–17 μM nitrate) and ~4,800 m (pH = 7.9; CO2 ~600 p.p.m.; 21 μM nitrate). Emiliania huxleyi strain CCMP 88E showed no differences in growth rate or in cellular content or production rates of particulate organic (POC) and inorganic (PIC) carbon and cellular particulate organic nitrogen (PON) between treatments using water from 1,000 m and 4,800 m. However, despite the N:P ratio of seawater being comparable in water from ~1,000 and ~4,800 m, the PON production rates were three times lower in one incubation using water from ~1,000 m compared to values observed in water from ~4,800 m. Thus, the POC:PON ratios were threefold higher in cells that were incubated in ~1,000 m seawater. The heavily calcified strain NZEH exhibited lower growth rates and PIC production rates when incubated in water from ~4,800 m compared to ~1,000 m, while cellular PIC, POC and PON were higher in water from 4,800 m. Calcite Sr/Ca ratios increased with depth despite constant seawater Sr/Ca, indicating that upwelling changes coccolith geochemistry. Our study provides the first experimental and field trial of a geoengineering approach to test how deep seawater impacts coccolithophore physiological and biogeochemical properties. Given that coccolithophore growth was only stimulated using waters obtained from >1,000 m, artificial upwelling using shallower waters may not be a suitable approach for promoting carbon sequestration for some locations and assemblages, and should therefore be investigated on a site-by-site basis.

High levels of solar radiation offset impacts of ocean acidification on calcifying and non-calcifying strains of Emiliania huxleyi

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 568:47-58 (2017) - DOI: https://doi.org/10.3354/meps12042 High levels of solar radiation offset impacts of ocean acidification on calcifying and non-calcifying strains of Emiliania huxleyi Peng Jin1, Jiancheng Ding1, Tao Xing1, Ulf Riebesell2, Kunshan Gao1,* 1State Key Laboratory of Marine Environmental Science/College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, PR China 2GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany *Corresponding author: ksgao@xmu.edu.cn ABSTRACT: Coccolithophores, a globally distributed group of marine phytoplankton, showed diverse responses to ocean acidification (OA) and to combinations of OA with other environmental factors. While their growth can be enhanced and calcification be hindered by OA under constant indoor light, fluctuation of solar radiation with ultraviolet irradiances might offset such effects. In this study, when a calcifying and a non-calcifying strain of Emiliania huxleyi were grown at 2 CO2 concentrations (low CO2 [LC]: 395 µatm; high CO2 [HC]: 1000 µatm) under different levels of incident solar radiation in the presence of ultraviolet radiation (UVR), HC and increased levels of solar radiation acted synergistically to enhance the growth in the calcifying strain but not in the non-calcifying strain. HC enhanced the particulate organic carbon (POC) and nitrogen (PON) productions in both strains, and this effect was more obvious at high levels of solar radiation. While HC decreased calcification at low solar radiation levels, it did not cause a significant effect at high levels of solar radiation, implying that a sufficient supply of light energy can offset the impact of OA on the calcifying strain. Our data suggest that increased light exposure, which is predicted to happen with shoaling of the upper mixing layer due to progressive warming, could counteract the impact of OA on coccolithophores distributed within this layer. KEY WORDS: Ocean acidification · Fluctuating light · UV radiation · Coccolithophore · Calcification Full text in pdf format Supplementary material PreviousNextCite this article as: Jin P, Ding J, Xing T, Riebesell U, Gao K (2017) High levels of solar radiation offset impacts of ocean acidification on calcifying and non-calcifying strains of Emiliania huxleyi. Mar Ecol Prog Ser 568:47-58. https://doi.org/10.3354/meps12042 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 568. Online publication date: March 24, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Ocean acidification effects on haploid and diploid Emiliania huxleyi strains: Why changes in cell size matter

The effects of ocean acidification (OA) on Emiliania huxleyi non-calcifying haploid strain CCMP 374 (s374) and calcifying diploid strain CCMP 2668 (s2668) were investigated in this study. Both E. huxleyi strains were cultured semi-continuously for ~20 generations under three pCO2 levels, one representing equilibrium with contemporary atmospheric pCO2 and two representing different OA scenarios projected for the end the century. During the course of the experiments, measurements were made for cell size in s374 and coccosphere size in strain s2668, cellular intrinsic growth rates, and the per cell (s374) and per coccosphere (s2668) concentrations of particulate organic carbon (POC) and nitrogen (PON), particulate inorganic carbon (PIC), chlorophyll a (chl a) and particulate dimethylsulfoniopropionate (DMSPp). In agreement with other studies, elevated pCO2 led to a small increase in POC and PON in the diploid strain, but not in the haploid strain. Although the PIC was static across pCO2 treatments in the diploid calcifier, PIC:POC was reduced under OA due to the disproportionate increase in POC. The concentration of E. huxleyi DMSPp cell−1 increased (s2668) or responded non-linearly (s374) to OA. Exposure to OA caused cell and coccosphere volumes to increase by 18% and 37% from the ambient to high pCO2 treatment in the haploid and diploid strain, respectively, despite equivalent cross-treatment growth rates. Therefore, when normalized to cell and coccosphere volume, small to negligible increases in cellular constituents under OA translated into decreased cellular and coccosphere densities (e.g. mass vol−1) of those same constituents. This produces seemingly contradictory cellular responses to OA depending on data normalization, and highlights the need to cautiously interpret OA experimental data when cell and coccosphere size is not reported. A consistent OA-induced increase in cell and coccosphere size has implications for E. huxleyi cellular physiology, ecology and trophic interactions, as cell size is a master characteristic that governs cellular rate processes, predator encounter rates, and predator ingestion efficiencies. Further, because POC and PON did not scale with volume increases, there is a dilution in the carbon and nitrogen concentration in E. huxleyi cells under OA. This result could have cascading effects on planktonic food webs as predator ingestion rates and growth efficiencies adjust.

Growth of the coccolithophore &amp;lt;i&amp;gt;Emiliania huxleyi&amp;lt;/i&amp;gt; in light- and nutrient-limited batch reactors: relevance for the BIOSOPE deep ecological niche of coccolithophores

Abstract. Coccolithophores are unicellular calcifying marine algae that play an important role in the oceanic carbon cycle via their cellular processes of photosynthesis (a CO2 sink) and calcification (a CO2 source). In contrast to the well-studied, surface-water coccolithophore blooms visible from satellites, the lower photic zone is a poorly known but potentially important ecological niche for coccolithophores in terms of primary production and carbon export to the deep ocean. In this study, the physiological responses of an Emiliania huxleyi strain to conditions simulating the deep niche in the oligotrophic gyres along the BIOSOPE transect in the South Pacific Gyre were investigated. We carried out batch culture experiments with an E. huxleyi strain isolated from the BIOSOPE transect, reproducing the in situ conditions of light and nutrient (nitrate and phosphate) limitation. By simulating coccolithophore growth using an internal stores (Droop) model, we were able to constrain fundamental physiological parameters for this E. huxleyi strain. We show that simple batch experiments, in conjunction with physiological modelling, can provide reliable estimates of fundamental physiological parameters for E. huxleyi that are usually obtained experimentally in more time-consuming and costly chemostat experiments. The combination of culture experiments, physiological modelling and in situ data from the BIOSOPE cruise show that E. huxleyi growth in the deep BIOSOPE niche is limited by availability of light and nitrate. This study contributes more widely to the understanding of E. huxleyi physiology and behaviour in a low-light and oligotrophic environment of the ocean.

Ocean acidification has different effects on the production of dimethylsulfide and dimethylsulfoniopropionate measured in cultures of Emiliania huxleyi and a mesocosm study: a comparison of laboratory monocultures and community interactions

Environmental context Approximately 25% of CO2 released to the atmosphere by human activities has been absorbed by the oceans, resulting in ocean acidification. We investigate the acidification effects on marine phytoplankton and subsequent production of the trace gas dimethylsulfide, a major route for sulfur transfer from the oceans to the atmosphere. Increasing surface water CO2 partial pressure (pCO2) affects the growth of phytoplankton groups to different degrees, resulting in varying responses in community production of dimethylsulfide. Abstract The human-induced rise in atmospheric carbon dioxide since the industrial revolution has led to increasing oceanic carbon uptake and changes in seawater carbonate chemistry, resulting in lowering of surface water pH. In this study we investigated the effect of increasing CO2 partial pressure (pCO2) on concentrations of volatile biogenic dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP), through monoculture studies and community pCO2 perturbation. DMS is a climatically important gas produced by many marine algae: it transfers sulfur into the atmosphere and is a major influence on biogeochemical climate regulation through breakdown to sulfate and formation of subsequent cloud condensation nuclei (CCN). Overall, production of DMS and DMSP by the coccolithophore Emiliania huxleyi strain RCC1229 was unaffected by growth at 900μatm pCO2, but DMSP production normalised to cell volume was 12% lower at the higher pCO2 treatment. These cultures were compared with community DMS and DMSP production during an elevated pCO2 mesocosm experiment with the aim of studying E. huxleyi in the natural environment. Results contrasted with the culture experiments and showed reductions in community DMS and DMSP concentrations of up to 60 and 32% respectively at pCO2 up to 3000μatm, with changes attributed to poorer growth of DMSP-producing nanophytoplankton species, including E. huxleyi, and potentially increased microbial consumption of DMS and dissolved DMSP at higher pCO2. DMS and DMSP production differences between culture and community likely arise from pH affecting the inter-species responses between microbial producers and consumers.

Losses, Expansions, and Novel Subunit Discovery of Adaptor Protein Complexes in Haptophyte Algae

The phylum Haptophyta (Diaphoratickes) contains marine algae that perform biomineralization, extruding large, distinctive calcium carbonate scales (coccoliths) that completely cover the cell. Coccolith production is an important part of global carbon cycling; however, the membrane trafficking pathway by which they are secreted has not yet been elucidated. In most eukaryotes, post-Golgi membrane trafficking involves five heterotetrameric adaptor protein (AP) complexes, which impart cargo selection specificity. To better understand coccolith secretion, we performed comparative genomic, phylogenetic, and transcriptomic analyses of the AP complexes in Emiliania huxleyi strains 92A, Van556, EH2, and CCMP1516, and related haptophytes Gephyrocapsa oceanica and Isochrysis galbana; the latter has lost the ability to biomineralize. We show that haptophytes have a modified membrane trafficking system (MTS), as we found both AP subunit losses and duplications. Additionally, we identified a single conserved subunit of the AP-related TSET complex, whose expression suggests a functional role in membrane trafficking. Finally, we detected novel alpha adaptin ear and gamma adaptin ear proteins, the first of their kind to be described outside of opisthokonts. These novel ear proteins and the sculpting of the MTS may support the capacity for biomineralization in haptophytes, enhancing their ability to perform this highly specialized form of secretion.

Large effect of irradiance on hydrogen isotope fractionation of alkenones in Emiliania huxleyi

The hydrogen isotopic (δD) composition of long-chain alkenones produced by certain haptophyte algae has been suggested as a potential proxy for reconstructing paleo sea surface salinity. However, environmental parameters other than salinity may also affect the δD of alkenones. We investigated the impact of the level of irradiance on hydrogen isotopic fractionation of alkenones versus growth water by cultivating two strains of the cosmopolitan haptophyte Emiliania huxleyi at different light intensities. The hydrogen isotope fractionation decreased by approximately 40‰ when irradiance was increased from 15 to 200μmolphotonsm−2s−1 above which it was relatively constant. The response is likely a direct effect of photosystem I and II activity as the relationship of the fractionation factor α versus light intensity can be described by an Eilers–Peeters photosynthesis model. This irradiance effect is in agreement with published δD data of alkenones derived from suspended particulate matter collected from different depths in the photic zone of the Gulf of California and the eastern tropical North Pacific. However, haptophyte algae tend to bloom at relatively high light intensities (>500μmolphotonsm−2s−1) occurring at the sea surface, at which hydrogen isotope fractionation is relatively constant and not affected by changes in light intensity. Alkenones accumulating in the sediment are likely mostly derived from these surface water haptophyte blooms, when the largest amount of biomass is produced. Therefore, the observed irradiance effect is unlikely to affect the applicability of the hydrogen isotopic composition of sedimentary long chain alkenones as a proxy for paleosalinity.

Effect of phosphorus limitation on coccolith morphology and element ratios in Mediterranean strains of the coccolithophore Emiliania huxleyi

Six Emiliania huxleyi strains isolated in the Mediterranean Sea were grown under phosphorus limitation and replete (control) conditions in batch culture. We tested the hypothesis that increasing phosphorus limitation, resulting from ocean warming, will affect coccolithophores and change their contribution to the PIC:POC ratios. Four strains were isolated in the oligotrophic Algerian basin (western Mediterranean), and two strains in the extremely oligotrophic and often phosphorus depleted Levantine basin (eastern Mediterranean). Samples for particulate inorganic carbon, PIC; particulate organic carbon, POC; particulate organic phosphorus, POP; and total particulate nitrogen, TPN, were taken at equal cell densities in phosphorus limited and control culture conditions (harvesting in exponential and stationary phases respectively). Different morphological features of coccoliths were analyzed. Phosphorus limitation was inferred from: 1. a decrease in growth rate between 22% and 34% compared to phosphorus replete cultures; 2. a reduction in final cell density from ca. 2×106cells/ml to ca. 8×104cells/ml, and 3. markedly lower POP quotas of the limited cells. Differences in the phosphate uptake machinery are suggested based on the fact that three western Mediterranean strains decreased the phosphate concentration in the culture media until the detection limit in the first 3 experimental days while 4–5days were necessary for the other strains. Cellular carbon quotas increased in all strains under phosphorus limitation in comparison to their respective control cultures. The increase in POC quotas ranged between 179% and 260% and in PIC quotas between 43% and 201%. TPN quotas increased under phosphorus limitation between 31% and 86% in five out of six strains. POC:TPN increased in all strains, which suggests a change in the molecular composition of the cells when exposed to phosphorus limitation. Strain specific responses were also observed in the PIC:POC ratio, which decreased in five strains and did not change in another. Phosphorus limitation did not lead to malformations. However, morphological changes of coccoliths occurred, also in a strain specific way, namely the percentage of over-calcified coccoliths was altered by P limitation, but we observed all signs in the responses among different strains. Nevertheless, this morphological feature does not reflect the changes in calcite production (PICp nor PIC:POC). Strain specific responses were not related to the isolation location, suggesting that the isolated western and eastern strains do not represent distinct eco-genotypes featuring different phosphorus usage strategies.

Strong shift from HCO3 (-) to CO 2 uptake in Emiliania huxleyi with acidification: new approach unravels acclimation versus short-term pH effects.

Effects of ocean acidification on Emiliania huxleyi strain RCC 1216 (calcifying, diploid life-cycle stage) and RCC 1217 (non-calcifying, haploid life-cycle stage) were investigated by measuring growth, elemental composition, and production rates under different pCO2 levels (380 and 950 μatm). In these differently acclimated cells, the photosynthetic carbon source was assessed by a 14C disequilibrium assay, conducted over a range of ecologically relevant pH values (7.9–8.7). In agreement with previous studies, we observed decreased calcification and stimulated biomass production in diploid cells under high pCO2, but no CO2-dependent changes in biomass production for haploid cells. In both life-cycle stages, the relative contributions of CO2 and HCO3 − uptake depended strongly on the assay pH. At pH values ≤ 8.1, cells preferentially used CO2 (≥ 90 % CO2), whereas at pH values ≥ 8.3, cells progressively increased the fraction of HCO3 − uptake (~45 % CO2 at pH 8.7 in diploid cells; ~55 % CO2 at pH 8.5 in haploid cells). In contrast to the short-term effect of the assay pH, the pCO2 acclimation history had no significant effect on the carbon uptake behavior. A numerical sensitivity study confirmed that the pH-modification in the 14C disequilibrium method yields reliable results, provided that model parameters (e.g., pH, temperature) are kept within typical measurement uncertainties. Our results demonstrate a high plasticity of E. huxleyi to rapidly adjust carbon acquisition to the external carbon supply and/or pH, and provide an explanation for the paradoxical observation of high CO2 sensitivity despite the apparently high HCO3 − usage seen in previous studies.Electronic supplementary materialThe online version of this article (doi:10.1007/s11120-014-9984-9) contains supplementary material, which is available to authorized users.

The trade‐off between the light‐harvesting and photoprotective functions of fucoxanthin‐chlorophyll proteins dominates light acclimation in Emiliania huxleyi (clone CCMP 1516)

Mechanistic understanding of the costs and benefits of photoacclimation requires knowledge of how photophysiology is affected by changes in the molecular structure of the chloroplast. We tested the hypothesis that changes in the light dependencies of photosynthesis, nonphotochemical quenching and PSII photoinactivation arises from changes in the abundances of chloroplast proteins in Emiliania huxleyi strain CCMP 1516 grown at 30 (Low Light; LL) and 1000 (High Light; HL) μmol photons m(-2) s(-1) photon flux densities. Carbon-specific light-saturated gross photosynthesis rates were not significantly different between cells acclimated to LL and HL. Acclimation to LL benefited cells by increasing biomass-specific light absorption and gross photosynthesis rates under low light, whereas acclimation to HL benefited cells by reducing the rate of photoinactivation of PSII under high light. Differences in the relative abundances of proteins assigned to light-harvesting (Lhcf), photoprotection (LI818-like), and the photosystem II (PSII) core complex accompanied differences in photophysiology: specifically, Lhcf:PSII was greater under LL, whereas LI818:PSII was greater in HL. Thus, photoacclimation in E. huxleyi involved a trade-off amongst the characteristics of light absorption and photoprotection, which could be attributed to changes in the abundance and composition of proteins in the light-harvesting antenna of PSII.

Pan genome of the phytoplankton Emiliania underpins its global distribution

Coccolithophores have influenced the global climate for over 200 million years. These marine phytoplankton can account for 20 per cent of total carbon fixation in some systems. They form blooms that can occupy hundreds of thousands of square kilometres and are distinguished by their elegantly sculpted calcium carbonate exoskeletons (coccoliths), rendering them visible from space. Although coccolithophores export carbon in the form of organic matter and calcite to the sea floor, they also release CO2 in the calcification process. Hence, they have a complex influence on the carbon cycle, driving either CO2 production or uptake, sequestration and export to the deep ocean. Here we report the first haptophyte reference genome, from the coccolithophore Emiliania huxleyi strain CCMP1516, and sequences from 13 additional isolates. Our analyses reveal a pan genome (core genes plus genes distributed variably between strains) probably supported by an atypical complement of repetitive sequence in the genome. Comparisons across strains demonstrate that E. huxleyi, which has long been considered a single species, harbours extensive genome variability reflected in different metabolic repertoires. Genome variability within this species complex seems to underpin its capacity both to thrive in habitats ranging from the equator to the subarctic and to form large-scale episodic blooms under a wide variety of environmental conditions.

Organic matter exudation by &amp;lt;I&amp;gt;Emiliania huxleyi&amp;lt;/I&amp;gt; under simulated future ocean conditions

Abstract. Emiliania huxleyi (strain B 92/11) was exposed to different nutrient supply, CO2 and temperature conditions in phosphorus controlled chemostats to investigate effects on organic carbon exudation and partitioning between the pools of particulate organic carbon (POC) and dissolved organic carbon (DOC). 14C incubation measurements for primary production (PP) and extracellular release (ER) were performed. Chemical analysis included the amount and composition of high molecular weight (&gt;1 kDa) dissolved combined carbohydrates (HMW-dCCHO), particulate combined carbohydrates (pCCHO) and the carbon content of transparent exopolymer particles (TEP-C). Applied CO2 and temperature conditions were 300, 550 and 900 μatm pCO2 at 14 °C, and additionally 900 μatm pCO2 at 18 °C simulating a greenhouse ocean scenario. Enhanced nutrient stress by reducing the dilution rate (D) from D = 0.3 d−1 to D = 0.1 d−1 (D = μ) induced the strongest response in E. huxleyi. At μ = 0.3 d−1, PP was significantly higher at elevated CO2 and temperature and DO14C production correlated to PO14C production in all treatments, resulting in similar percentages of extracellular release (PER; (DO14C production/PP) × 100) averaging 3.74 ± 0.94%. At μ = 0.1 d−1, PO14C production decreased significantly, while exudation of DO14C increased. Thus, indicating a stronger partitioning from the particulate to the dissolved pool. Maximum PER of 16.3 ± 2.3% were observed at μ = 0.1 d−1 at elevated CO2 and temperature. While cell densities remained constant within each treatment and throughout the experiment, concentrations of HMW-dCCHO, pCCHO and TEP were generally higher under enhanced nutrient stress. At μ = 0.3 d−1, pCCHO concentration increased significantly with elevated CO2 and temperature. At μ = 0.1 d−1, the contribution (mol % C) of HMW-dCCHO to DOC was lower at elevated CO2 and temperature while pCCHO and TEP concentrations were higher. This was most pronounced under greenhouse conditions. Our findings suggest a stronger transformation of primary produced DOC into POC by coagulation of exudates under nutrient limitation. Our results further imply that elevated CO2 and temperature will increase exudation by E. huxleyi and may affect organic carbon partitioning in the ocean due to an enhanced transfer of HMW-dCCHO to TEP by aggregation processes.

Reduced Calcification Decreases Photoprotective Capability in the Coccolithophorid Emiliania huxleyi

Intracellular calcification of coccolithophores generates CO₂ and consumes additional energy for acquisition of calcium and bicarbonate ions; therefore, it may correlate with photoprotective processes by influencing the energetics. To address this hypothesis, a calcifying Emiliania huxleyi strain (CS-369) was grown semi-continuously at reduced (0.1 mM, LCa) and ambient Ca²⁺ concentrations (10 mM, HCa) for 150 d (>200 generations). The HCa-grown cells had higher photosynthetic and calcification rates and higher contents of Chl a and carotenoids compared with the naked (bearing no coccoliths) LCa-grown cells. When exposed to stressfull levels of photosynthetically active radiation (PAR), LCa-grown cells displayed lower photochemical yield and less efficient non-photochemical quenching (NPQ). When the LCa- or HCa-grown cells were inversely shifted to their counterpart medium, LCa to HCa transfer increased photosynthetic carbon fixation (P), calcification rate (C), the C/P ratio, NPQ and pigment contents, whereas those shifted from HCa to LCa exhibited the opposite effects. Increased NPQ, carotenoids and quantum yield were clearly linked with increased or sustained calcification in E. huxleyi. The calcification must have played a role in dissipating excessive energy or as an additional drainage of electrons absorbed by the photosynthetic antennae. This phenomenon was further supported by testing two non-calcifying strains, which showed insignificant changes in photosynthetic carbon fixation and NPQ when transferred to LCa conditions.

Changes in Emiliania huxleyi fatty acid profiles during infection with E. huxleyi virus 86: physiological and ecological implications

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 55:219-228 (2009) - DOI: https://doi.org/10.3354/ame01295 Changes in Emiliania huxleyi fatty acid profiles during infection with E. huxleyi virus 86: physiological and ecological implications Claire Evans1,3, David W. Pond2, William H. Wilson1,4,* 1Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK 2British Antarctic Survey, Natural Environmental Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK 3Present address: Department of Biological Oceanography, Royal Netherlands Institute for Sea Research, PO Box 59, 1790 AB Den Burg, Texel, The Netherlands 4Present address: Bigelow Laboratory for Ocean Sciences, 180 McKown Point Road, PO Box 475, West Boothbay Harbor, Maine 04575, USA *Corresponding author. Email: wwilson@bigelow.org ABSTRACT: Fatty acids profiles of Emiliania huxleyi strain CCMP1516 were determined in a virus-induced culture crash with E. huxleyi virus 86 (EhV-86). As cell numbers declined in the infected cultures due to virus lysis, a concomitant decrease in fatty acids was observed in the particulate fraction. The composition of fatty acids within infected E. huxleyi cells was restructured, with a shift from polyunsaturated to monounsaturated and saturated fatty acids (respective distributions changing from 70:10:20% at the start of the experiment to 44:24:32% at the final time point). In particular, decreases were seen in the major fatty acid 22:6(n-3) and in 18:5(n-3), whereas greatest increases were seen in 18:1(n-9) and 22:0. The increase in the amount and restructuring of the fatty acid pool in E. huxleyi was indicative of a combination of specific and non-specific effects of virus infection. Specific effects primarily included induction of metabolic pathways such as the synthesis of components involved in virus replication, the production of virions and signal transduction via sphingolipid biosynthesis. Non-specific effects due to stress were likely mediated by reactive oxygen species. Changes in the composition of virus-infected E. huxleyi are of significance to the food web since grazing on virus-infected blooms will decrease the amount of essential polyunsaturated fatty acids passed on to higher trophic levels. Consequently, this could decrease the overall productivity of marine ecosystems. KEY WORDS: Emiliania huxleyi · Virus · Fatty acids · Lipids · Virus infection · Oxidative stress Full text in pdf format PreviousNextCite this article as: Evans C, Pond DW, Wilson WH (2009) Changes in Emiliania huxleyi fatty acid profiles during infection with E. huxleyi virus 86: physiological and ecological implications. Aquat Microb Ecol 55:219-228. https://doi.org/10.3354/ame01295Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 55, No. 3. Online publication date: May 08, 2009 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2009 Inter-Research.