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1.
There is still considerable uncertainty about the relationship between calcification and photosynthesis. It has been suggested that since calcification in coccolithophorids is an intracellular process that releases CO2, it enhances photosynthesis in a manner analogous to a carbon‐concentrating mechanism (CCM). The ubiquitous, bloom‐forming, and numerically abundant coccolithophorid Emiliania huxleyi (Lohmann) W. W. Hay et H. Mohler was studied in nutrient‐replete, pH and [CO2] controlled, continuous cultures (turbidostats) under a range of [Ca2+] from 0 to 9 mM. We examined the long‐term, fully acclimated photosynthesis‐light responses and analyzed the crystalline structure of the coccoliths using SEM. The E. huxleyi cells completely lost their coccosphere when grown in 0 [Ca2+], while thin, undercalcified and brittle coccoliths were evident at 1 mM [Ca2+]. Coccoliths showed increasing levels of calcification with increasing [Ca2+]. More robust coccoliths were noted, with no discernable differences in coccolith morphology when the cells were grown in either 5 or 9 mM (ambient seawater) [Ca2+]. In contrast to calcification, photosynthesis was not affected by the [Ca2+] in the media. Cells showed no correlation of their light‐dependent O2 evolution with [Ca2+], and in all [Ca2+]‐containing turbidostats, there were no significant differences in growth rate. The results show unequivocally that as a process, photosynthesis in E. huxleyi is mechanistically independent from calcification. 相似文献
2.
Cornelis Linschooten Judith D. L. van Bleijswijk Peter R. van Emburg Johannes P. M. de Vrind Egbert S. Kempers Peter Westbroek Elisabeth W. de Vrind-de Jong 《Journal of phycology》1991,27(1):82-86
Production of coccoliths by cells of Emiliania huxleyi (Lohmann) Hay and Mohler was measured during exposure of the cells to two diel light-dark cycles (16:8 h). During the light period about eight coccoliths per cell were formed at a constant rate of one coccolith per 2 h. Cells divided during the first half of the dark period. No coccolith production took place during the dark period. With electron microscopy we found early-stage, coccolith-production compartments in cells after mitosis while still in the dark. No calcification was observed in these compartments. Cells grown on enriched seawater (Eppley's medium) tended to produce enough coccoliths to cover the cell in a single layer. When these cells reached the stationary phase coccolith production stopped. Coccolith production was induced by removal of extracellular coccoliths. Cells grown on medium containing 2% of the nitrate and phosphate of Eppley's medium tended to produce coccoliths in the stationary phase. This resulted in the formation of multiple layers of coccoliths. The multiple covering was restored after decalcification of stationary cells. Formation of multiple layers of coccoliths may help the cells reach deeper, nutrient-rich water by increasing the sinking rate of the cells. 相似文献
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Increasing anthropogenic carbon dioxide is causing changes to ocean chemistry, which will continue in a predictable manner. Dissolution of additional atmospheric carbon dioxide leads to increased concentrations of dissolved carbon dioxide and bicarbonate and decreased pH in ocean water. The concomitant effects on phytoplankton ecophysiology, leading potentially to changes in community structure, are now a focus of concern. Therefore, we grew the coccolithophore Emiliania huxleyi (Lohmann) W. W. Hay et H. Mohler and the diatom strains Thalassiosira pseudonana (Hust.) Hasle et Heimdal CCMP 1014 and T. pseudonana CCMP 1335 under low light in turbidostat photobioreactors bubbled with air containing 390 ppmv or 750 ppmv CO2. Increased pCO2 led to increased growth rates in all three strains. In addition, protein levels of RUBISCO increased in the coastal strains of both species, showing a larger capacity for CO2 assimilation at 750 ppmv CO2. With increased pCO2, both T. pseudonana strains displayed an increased susceptibility to PSII photoinactivation and, to compensate, an augmented capacity for PSII repair. Consequently, the cost of maintaining PSII function for the diatoms increased at increased pCO2. In E. huxleyi, PSII photoinactivation and the counter‐acting repair, while both intrinsically larger than in T. pseudonana, did not change between the current and high‐pCO2 treatments. The content of the photosynthetic electron transport intermediary cytochrome b6/f complex increased significantly in the diatoms under elevated pCO2, suggesting changes in electron transport function. 相似文献
5.
Kai T. Lohbeck Ulf Riebesell Thorsten B. H. Reusch 《Proceedings. Biological sciences / The Royal Society》2014,281(1786)
Coccolithophores are unicellular marine algae that produce biogenic calcite scales and substantially contribute to marine primary production and carbon export to the deep ocean. Ongoing ocean acidification particularly impairs calcifying organisms, mostly resulting in decreased growth and calcification. Recent studies revealed that the immediate physiological response in the coccolithophore Emiliania huxleyi to ocean acidification may be partially compensated by evolutionary adaptation, yet the underlying molecular mechanisms are currently unknown. Here, we report on the expression levels of 10 candidate genes putatively relevant to pH regulation, carbon transport, calcification and photosynthesis in E. huxleyi populations short-term exposed to ocean acidification conditions after acclimation (physiological response) and after 500 generations of high CO2 adaptation (adaptive response). The physiological response revealed downregulation of candidate genes, well reflecting the concomitant decrease of growth and calcification. In the adaptive response, putative pH regulation and carbon transport genes were up-regulated, matching partial restoration of growth and calcification in high CO2-adapted populations. Adaptation to ocean acidification in E. huxleyi likely involved improved cellular pH regulation, presumably indirectly affecting calcification. Adaptive evolution may thus have the potential to partially restore cellular pH regulatory capacity and thereby mitigate adverse effects of ocean acidification. 相似文献
6.
María Dbora Iglesias‐Rodríguez Oscar M. Schofield Jacqueline Batley Linda K. Medlin Paul K. Hayes 《Journal of phycology》2006,42(3):526-536
Using primer pairs for seven previously described microsatellite loci and three newly characterized microsatellite loci from the coccolithophore Emiliania huxleyi (Lohm.) Hay and Mohler, we assessed genetic variation within this species. Analysis of microsatellite length variants (alleles) was conducted for 85 E. huxleyi isolates representative of different ocean basins. These results revealed high intraspecific genetic variability within the E. huxleyi species concept. Pairwise comparison of a 1992 Coastal Fjord group (FJ92) (n=41) and a North East Atlantic (NEA) group (n=21), using FST as an indicator of genetic differentiation, revealed moderate genetic differentiation (FST=0.09894; P=0; significance level=0.05). Gene flow between the FJ92 and NEA groups was estimated to be low, which is in agreement with the moderate levels of genetic differentiation revealed by the microsatellite data. A genetic assignment method that uses genotype likelihoods to draw inference about the groups to which individuals belong was tested. Using FJ92 and NEA as reference groups, we observed that all the E. huxleyi groups tested against the two reference groups were unrelated to them. On a global biogeographical scale, E. huxleyi populations appear to be highly genetically diverse. Our findings raise the question of whether such a high degree of intraspecific genetic diversity in coccolithophores translates into variability in ecological function. 相似文献
7.
Paul L. A. M. Corstjens Annemieke van der Kooij Cornelis Linschooten Geert-Jan Brouwers Peter Westbroek Elisabeth W. de Vrind-de Jong 《Journal of phycology》1998,34(4):622-630
Intracellular polysaccharide fractions were isolated from calcifying B-type cells of Emiliania huxleyi and separated by electrophoretic fractionation. In all fractions, the polysaccharide was immunologically related to the polysaccharide of (extracellular) B-type coccoliths (CP-B) and not to polysaccharides of A-type coccoliths (CP-A). Most polysaccharide fractions also contained protein material. The fraction with the largest proportion of protein was used to raise antibodies. The resulting antiserum, α-BP, contained antibodies against both CP-B- and protein-epitopes. The antibodies specific for polysaccharide-epitopes reacted with intracellular polysaccharide fractions of B-type cells only. In contrast, the antibodies specific for protein-epitopes reacted with the intracellular fractions of B-type as well as A-type cells. With immunolocalization, the presence of protein antigen in a layer surrounding both types of cells was demonstrated. A cDNA library of E. huxleyi was screened with α-BP, and a gene called gpa was isolated. The open reading frame of gpa was found to encode a protein (GPA) of 36,608 D, containing, inter alia, 24% acidic residues (18% glutamic acid and 6% aspartic acid), 12% proline, and 23% alanine. GPA has two repeats, one containing a sequence resembling the Ca2+ -binding loop of EF-hands. Overproduction of GPA in a prokaryotic system yielded a dimeric product capable of binding Ca2+ . The possible role of GPA in the formation of coccoliths in E. huxleyi is discussed. 相似文献
8.
Marianne V. Nielsen 《Journal of phycology》1995,31(5):715-719
Light-saturated photosynthesis (Pmax) of Emiliania huxleyi (Lohmann) Hay et Mohler is known to be carbonlimited at natural concentrations of dissolved inorganic carbon (DIC). In the present study, light-limited and light-saturated photosynthetic rates of E. huxleyi were studied at three concentrations of DIC (2.4, 7.4, and 12.4 mM) for high-calcite (Cin/Ctot=0.48) and low-calcite (Cin/Ctot=0.08) cells of the same strain. The photosynthetic efficiency (α) and the maximum quantum yield (θmax)A increased by more than a factor of 2 from the lowest to the highest DIC level. Pmax a, and θmax were always higher for the high-calcite than for the low-calcite cells at identical DIC levels. This may indicate that the calcifcation process acts as an extra supplier of CO2 for photosynthesis making the CO2 shortage at natural DIC levels a little smaller for high-calcite than for low-calcite E. huxleyi. A dependency of θmax on DIC has not previously been shown for marine phytoplankton. θmax is a key parameter in recent biooptical models of phytoplankton productivity, and the results from the present study are therefore important for modeling the productivity of E. huxleyi. 相似文献
9.
Yuanyuan Feng Michael Y. Roleda Evelyn Armstrong Tina C. Summerfield Cliff S. Law Catriona L. Hurd Philip W. Boyd 《Global Change Biology》2020,26(10):5630-5645
Ongoing ocean global change due to anthropogenic activities is causing multiple chemical and physical seawater properties to change simultaneously, which may affect the physiology of marine phytoplankton. The coccolithophore Emiliania huxleyi is a model species often employed in the study of the marine carbon cycle. The effect of ocean acidification (OA) on coccolithophore calcification has been extensively studied; however, physiological responses to multiple environmental drivers are still largely unknown. Here we examined two‐way and multiple driver effects of OA and other key environmental drivers—nitrate, phosphate, irradiance, and temperature—on the growth, photosynthetic, and calcification rates, and the elemental composition of E. huxleyi. In addition, changes in functional gene expression were examined to understand the molecular mechanisms underpinning the physiological responses. The single driver manipulation experiments suggest decreased nitrate supply being the most important driver regulating E. huxleyi physiology, by significantly reducing the growth, photosynthetic, and calcification rates. In addition, the interaction of OA and decreased nitrate supply (projected for year 2100) had more negative synergistic effects on E. huxleyi physiology than all other two‐way factorial manipulations, suggesting a linkage between the single dominant driver (nitrate) effects and interactive effects with other drivers. Simultaneous manipulation of all five environmental drivers to the conditions of the projected year 2100 had the largest negative effects on most of the physiological metrics. Furthermore, functional genes associated with inorganic carbon acquisition (RubisCO, AEL1, and δCA) and calcification (CAX3, AEL1, PATP, and NhaA2) were most downregulated by the multiple driver manipulation, revealing linkages between responses of functional gene expression and associated physiological metrics. These findings together indicate that for more holistic projections of coccolithophore responses to future ocean global change, it is necessary to understand the relative importance of environmental drivers both individually (i.e., mechanistic understanding) and interactively (i.e., cumulative effect) on coccolithophore physiology. 相似文献
10.
Stephane C. Lefebvre Ina Benner Jonathon H. Stillman Alexander E. Parker Michelle K. Drake Pascale E. Rossignol Kristine M. Okimura Tomoko Komada Edward J. Carpenter 《Global Change Biology》2012,18(2):493-503
Coccolithophores are unicellular phytoplankton that produce calcium carbonate coccoliths as an exoskeleton. Emiliania huxleyi, the most abundant coccolithophore in the world's ocean, plays a major role in the global carbon cycle by regulating the exchange of CO2 across the ocean‐atmosphere interface through photosynthesis and calcium carbonate precipitation. As CO2 concentration is rising in the atmosphere, the ocean is acidifying and ammonium (NH4+) concentration of future ocean water is expected to rise. The latter is attributed to increasing anthropogenic nitrogen (N) deposition, increasing rates of cyanobacterial N2 fixation due to warmer and more stratified oceans, and decreased rates of nitrification due to ocean acidification. Thus, future global climate change will cause oceanic phytoplankton to experience changes in multiple environmental parameters including CO2, pH, temperature and nitrogen source. This study reports on the combined effect of elevated pCO2 and increased NH4+ to nitrate (NO3?) ratio (NH4+/NO3?) on E. huxleyi, maintained in continuous cultures for more than 200 generations under two pCO2 levels and two different N sources. Herein, we show that NH4+ assimilation under N‐replete conditions depresses calcification at both low and high pCO2, alters coccolith morphology, and increases primary production. We observed that N source and pCO2 synergistically drive growth rates, cell size, and the ratio of inorganic to organic carbon. These responses to N source suggest that, compared to increasing CO2 alone, a greater disruption of the organic carbon pump could be expected in response to the combined effect of increased NH4+/NO3? ratio and CO2 level in the future acidified ocean. Additional experiments conducted under lower nutrient conditions are needed prior to extrapolating our findings to the global oceans. Nonetheless, our results emphasize the need to assess combined effects of multiple environmental parameters on phytoplankton biology to develop accurate predictions of phytoplankton responses to ocean acidification. 相似文献
11.
M. Dbora Iglesias‐Rodríguez Alberto G. Sez Ren Groben Keith J. Edwards Jacqueline Batley Linda K. Medlin Paul K. Hayes 《Molecular ecology resources》2002,2(4):495-497
The marine coccolithophorid Emiliania huxleyi is an important component of the marine carbon cycle because bloom development results in the export of calcium carbonate from the ocean surface to the abyss. Laboratory and field studies demonstrate significant biogeographical, ecological, physiological and morphological plasticity in E. huxleyi and suggest high underlying genetic variability. Here we describe seven polymorphic microsatellite loci from the E. huxleyi genome and their degree of polymorphism in clonal isolates of different geographical origin. Our results indicate a high degree of genetic diversity within E. huxleyi. 相似文献
12.
The response of the coccolithophorid Emiliania huxleyi (Lohmann) W. H. Hay et H. Mohler to acute exposure to high photon flux densities (PFD) was examined in terms of PSII photoinhibition, photoprotection, and photorepair. The time and light dependencies of these processes were characterized as a function of the photoacclimation state of the alga. Low‐light (LL) acclimated cells displayed a higher degree of photoinhibition, measured as decline in Fv/Fm, than high‐light (HL) acclimated cells. However, HL cultures were more susceptible to photodamage but also more capable of compensating for it by performing a faster repair cycle. The relation between gross photoinhibition (observed in the presence of an inhibitor of repair) and PFD to which the algae were exposed deviated from linearity at high PFD, which calls into question the universality of current concepts of photoinhibition in mechanistic models. The light dependence of the de‐epoxidation state (DPS) of the xanthophyll cycle (XC) pigments on the timescale of hours was the same in cells acclimated to LL and HL. However, HL cells were more efficient in realizing nonphotochemical quenching (NPQ) on short timescales, most likely due to a larger XC pool. LL cells displayed an increase in the PSII effective cross‐section (σPSII) as a result of photoinhibition, which was observed also in HL cells when net photoinhibition was induced by blocking the D1 repair cycle. The link between σPSII and photoinhibition suggests that the population of PSII reaction centers (RCIIs) of E. huxleyi shares a common antenna, according to a “lake” organization of the light‐harvesting complex. 相似文献
13.
Declan C. Schroeder Gaia F. Biggi Matthew Hall Joanne Davy Joaquín Martínez Martínez Anthony J. Richardson Gillian Malin William H. Wilson 《Journal of phycology》2005,41(4):874-879
Emiliania huxleyi (Lohm.) Hay and Mohler is a ubiquitous unicellular marine alga surrounded by an elaborate covering of calcite platelets called coccoliths. It is an important primary producer involved in oceanic biogeochemistry and climate regulation. Currently, E. huxleyi is separated into five morphotypes based on morphometric, physiological, biochemical, and immunological differences. However, a genetic marker has yet to be found to characterize these morphotypes. With the use of sequence analysis and denaturing gradient gel electrophoresis, we discovered a genetic marker that correlates significantly with the separation of the most widely recognized A and B morphotypes. Furthermore, we reveal that the A morphotype is composed of a number of distinct genotypes. This marker lies within the 3′ untranslated region of a coccolith associated protein mRNA, which is implicated in regulating coccolith calcification. Consequently, we tentatively termed this marker the coccolith morphology motif. 相似文献
14.
The production of the marine trace gas dimethyl sulfide (DMS) provides 90% of the marine biogenic sulfur in the atmosphere where it affects cloud formation and climate. The effects of increasing anthropogenic CO2 and the resulting warming and ocean acidification on trace gas production in the oceans are poorly understood. Here we report the first measurements of DMS‐production and data on growth, DMSP and DMS concentrations in pH‐stated cultures of the phytoplankton haptophyte Emiliania huxleyi. Four different environmental conditions were tested: ambient, elevated CO2 (+CO2), elevated temperature (+T) and elevated temperature and CO2 (+TCO2). In comparison to the ambient treatment, average DMS production was about 50% lower in the +CO2 treatment. Importantly, temperature had a strong effect on DMS production and the impacts outweighed the effects of a decrease in pH. As a result, the +T and +TCO2 treatments showed significantly higher DMS production of 36.2 ± 2.58 and 31.5 ± 4.66 μmol L?1 cell volume (CV) h?1 in comparison with the +CO2 treatment (14.9 ± 4.20 μmol L?1 CV h?1). As the cultures were aerated with an air/CO2 mixture, DMS was effectively removed from the incubation bottles so that concentration remained relatively low (3.6–6.1 mmol L?1 CV). Intracellular DMSP has been shown to increase in E. huxleyi as a result of elevated temperature and/or elevated CO2 and our results are in agreement with this finding: the ambient and +CO2 treatments showed 125 ± 20.4 and 162 ± 27.7 mmol L?1 CV, whereas +T and +TCO2 showed significantly increased intracellular DMSP concentrations of 195 ± 15.8 and 211 ± 28.2 mmol L?1 CV respectively. Growth was unaffected by the treatments, but cell diameter decreased significantly under elevated temperature. These results indicate that DMS production is sensitive to CO2 and temperature in E. huxleyi. Hence, global environmental change that manifests in ocean acidification and warming may not result in decreased DMS as suggested by earlier studies investigating the effect of elevated CO2 in isolation. 相似文献
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Dufault AM Cumbo VR Fan TY Edmunds PJ 《Proceedings. Biological sciences / The Royal Society》2012,279(1740):2951-2958
Manipulative studies have demonstrated that ocean acidification (OA) is a threat to coral reefs, yet no experiments have employed diurnal variations in pCO(2) that are ecologically relevant to many shallow reefs. Two experiments were conducted to test the response of coral recruits (less than 6 days old) to diurnally oscillating pCO(2); one exposing recruits for 3 days to ambient (440 μatm), high (663 μatm) and diurnally oscillating pCO(2) on a natural phase (420-596 μatm), and another exposing recruits for 6 days to ambient (456 μatm), high (837 μatm) and diurnally oscillating pCO(2) on either a natural or a reverse phase (448-845 μatm). In experiment I, recruits exposed to natural-phased diurnally oscillating pCO(2) grew 6-19% larger than those in ambient or high pCO(2). In experiment II, recruits in both high and natural-phased diurnally oscillating pCO(2) grew 16 per cent larger than those at ambient pCO(2), and this was accompanied by 13-18% higher survivorship; the stimulatory effect on growth of oscillatory pCO(2) was diminished by administering high pCO(2) during the day (i.e. reverse-phased). These results demonstrate that coral recruits can benefit from ecologically relevant fluctuations in pCO(2) and we hypothesize that the mechanism underlying this response is highly pCO(2)-mediated, night-time storage of dissolved inorganic carbon that fuels daytime calcification. 相似文献
17.
The relationships among inorganic carbon transport, bicarbonate availability, intracellular pH, and culture age were investigated in high-calcifying cultures of Emiliania huxleyi (Lohmann) Hay & Mohler. Measurement of inorganic carbon transport by the silicone-oil centrifugation technique demonstrated that gadolinium, a potential Ca2+ channel inhibitor, blocked intracellular inorganic carbon uptake and photosynthetic 14CO2+ fixation in exponential-phase cells. In stationary-phase cells, the intracellular inorganic carbon concentration was unaffected by gadolinium. Gadolinium was also used to investigate the link between bicarbonate and Ca2+ transport in high-calcifying cells of E. huxleyi. Bicarbonate availability had significant and rapid effects on pHi in exponential- but not in stationary-phase cells. 4′, 4′-Diisothiocyanostilbene-2,2′-disulfonic acid did not block bicarbonate uptake from the external medium by exponential-phase cells. Inorganic carbon utilization by exponential- and stationary-phase cells of Emiliania huxleyi was investigated using a pH drift technique in a closed system. Light-dependent alkalization of the medium by stationary-phase cells resulted in a final pH of 10.1 and was inhibited by dextran-bound sulphonamide, an inhibitor of external carbonic anhydrase. Exponential-phase cells did not generate a pH drift. Overall, the results suggest that for high-calcifying cultures of E. huxleyi the predominant pathway of inorganic carbon utilization differs in exponential and stationary phase cells of the same culture. 相似文献
18.
This study tested the hypothesis that the response of corals to temperature and pCO 2 is consistent between taxa. Juvenile massive Porites spp. and branches of P. rus from the back reef of Moorea were incubated for 1 month under combinations of temperature (29.3 °C and 25.6 °C) and pCO 2 (41.6 Pa and 81.5 Pa) at an irradiance of 599 μmol quanta m?2 s?1. Using microcosms and CO2 gas mixing technology, treatments were created in a partly nested design (tanks) with two between‐plot factors (temperature and pCO 2), and one within‐plot factor (taxon); calcification was used as a dependent variable. pCO 2 and temperature independently affected calcification, but the response differed between taxa. Massive Porites spp. was largely unaffected by the treatments, but P. rus grew 50% faster at 29.3 °C compared with 25.6 °C, and 28% slower at 81.5 Pa vs. 41.6 Pa CO2. A compilation of studies placed the present results in a broader context and tested the hypothesis that calcification for individual coral genera is independent of pH, [HCO3 ?], and [CO3 2?]. Unlike recent reviews, this analysis was restricted to studies reporting calcification in units that could be converted to nmol CaCO3 cm?2 h?1. The compilation revealed a high degree of variation in calcification as a function of pH, [HCO3 ?], and [CO3 2?], and supported three conclusions: (1) studies of the effects of ocean acidification on corals need to pay closer attention to reducing variance in experimental outcomes to achieve stronger synthetic capacity, (2) coral genera respond in dissimilar ways to pH, [HCO3 ?], and [CO3 2?], and (3) calcification of massive Porites spp. is relatively resistant to short exposures of increased pCO 2, similar to that expected within 100 y. 相似文献
19.
Coccolithophores are the most abundant calcifying organisms in modern oceans and are important primary producers in many marine ecosystems. Their ability to generate a cellular covering of calcium carbonate plates (coccoliths) plays a major role in marine biogeochemistry and the global carbon cycle. Coccolithophores also play an important role in sulfur cycling through the production of the climate-active gas dimethyl sulfide. The primary model organism for coccolithophore research is Emiliania huxleyi, now named Gephyrocapsa huxleyi. G. huxleyi has a cosmopolitan distribution, occupying coastal and oceanic environments across the globe, and is the most abundant coccolithophore in modern oceans. Research in G. huxleyi has identified many aspects of coccolithophore biology, from cell biology to ecological interactions. In this perspective, we summarize the key advances made using G. huxleyi and examine the emerging tools for research in this model organism. We discuss the key steps that need to be taken by the research community to advance G. huxleyi as a model organism and the suitability of other species as models for specific aspects of coccolithophore biology. 相似文献
20.
Judith D. L. van Bleijswijk Rob S. Kempers Marcel J. Veldhuis Peter Westbroek 《Journal of phycology》1994,30(2):230-241
Two morphotypes of Emiliania huxleyi (Lohmann 1902) Hay et al. 1967, types A and B, known to be unequally distributed in the oceans, were grown in dilution cultures at a range of photon flux densities (PFDs) (1.5–155 μmol photons·m?2·s?1) and two temperatures (10° and 15° C). Calcite carbon and organic carbon content of the cells as well as instantaneous growth rate, cell size, chlorophyll fluorescence, and light-scatter properties clearly depended on growth conditions and differed considerably for the two morphotypes. The ratio between calcite carbon and organic carbon production showed an optimum of 0.65 in E. huxleyi type A cells at PFD = 17.5. The ratio increased slightly with a temperature increase from 10° to 15°C but remained < 1.0 at both temperatures in light-limited cells. In contrast, calcite carbon production exceeded organic carbon production (ratio: 1.4–2.2) in phosphate-deprived cultures. Emiliania huxleyi type B generally showed a higher calcite carbon/organic carbon ratio than E. huxleyi type A, but the relation with PFD was similar. The content of calcite carbon and organic carbon as well as the instantaneous growth rate, cell size, chlorophyll fluorescence, and light-scatter properties showed large diel variations that were closely related to the division cycle. Our results show the importance of mapping the structure of any sampled cell population with respect to the phase in the cell division cycle, as this largely determines the outcome of not only “per cell” measurements but also short time (less than 24 h) flux measurements. For instance, dark production of calcite by E. huxleyi was negatively affected by cell division. Slowly growing (phosphate-stressed) cultures produced calcite in the light and in the dark. In contrast, rapidly growing cultures at 10°C produced calcite only in the light, whereas in the dark there was a significant loss of calcite due to dissolution. 相似文献