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Culture experiments were used to assess the applicability of Emiliania huxleyi coccolith morphology as a palaeo-sea-surface salinity (SSS) proxy. Coccolith morphology was dependent on salinity over a range reflecting present day marine conditions; both coccolith size and the number of coccolith elements increased linearly with increasing salinity....

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... were captured using a Philips XL30 SEM on 30 detached, flat-lying coccoliths per sample. Length and width of both the coccolith distal shield (DL and DW, respectively) and the central area (CAL and CAW, respectively) were measured and the number of distal shield elements (NE) was counted ( Fig. 1) using ImageJ 1.38 (http://rsb.info.nih.gov/ij/) at a resolution of 0.008 mm. Measurements were calibrated using 2-mm microsphere standards (Duke Scientific). The mean values of each morphological variable were calculated for each ...
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... et al. In press) found E. huxleyi coccoliths to increase in size linearly with increasing salinities from 32 to 39 (sediment core-top data outside this salinity range are discussed later). The degree of high similarity in slopes between the coccolith morphol- ogy vs. salinity regressions for culture and for plankton and sediment core-top data ( Fig. 3B; Table 1) supports the hypothesis that salinity increase causes the linear change in E. huxleyi coccolith size observed in the ocean ( Bollmann and Herrle 2007). However, the higher intercept of the morphological data presented here indicates that the absolute sizes of coccoliths at any given salinity may be larger for culture than for ...
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... for natural E. huxleyi growth conditions; Kirk 1994; Cort ́s et al. 2001) continuous light (Philips TL-D/865 Super 80). The use of continuous light ensured that cultures did not undergo synchronized division, which could bias results (Mu ̈ ller et al. 2008). ASW was made using deionized water, 0.5 g Tricine L 2 1 (Sigma, T-0377) to prevent precipitation of salts during autoclaving, and variable concentrations of synthetic sea salt (Ultramarine, Waterlife Research Industries). After autoclaving, f/2 enrichment media was added (Sigma, G0154; Guillard 1975). Salinities were determined using an Autosal 8400 (Guildline Instru- ments). Cultures were grown at 10 salinities (between 18 and 41) and at four temperatures (between 10 u C and 20 u C). Cultures were acclimated to each treatment for . 10 generations. Throughout acclimation and subsequent experimentation, cultures were mixed twice daily and maintained in exponen- tial growth phase at cell concentrations below 3.0 3 10 4 cells mL 2 1 . Acclimated specific growth rates were between 0.05 d 2 1 and 0.7 d 2 1 (salinity gradient) and 0.2 d 2 1 and 0.95 d 2 1 (temperature gradient). In mid-exponential phase, one sample from each treatment was taken for coccolith morphological analysis using a scanning electron micro- scope (SEM). Samples were filtered onto polycarbonate filters (0.4- m m pore size), rinsed in NH 4 OH-buffered H 2 O (pH 8.5), mounted on stubs, and sputter-coated with , 15 nm of gold-palladium. Cultures grown below a salinity of 26 failed to produce sufficient coccoliths and were excluded from analysis. Images were captured using a Philips XL30 SEM on 30 detached, flat-lying coccoliths per sample. Length and width of both the coccolith distal shield (DL and DW, respectively) and the central area (CAL and CAW, respectively) were measured and the number of distal shield elements (NE) was counted ( Fig. 1) using ImageJ 1.38 ( at a resolution of 0.008 m m. Measurements were calibrated using 2- m m microsphere standards (Duke Scientific). The mean values of each morphological variable were calculated for each treatment. Statistical analysis— Least squares linear regressions of each morphological variable as a function of salinity were calculated from data collected at 15 u C, and slopes were tested against the null hypothesis that they were not significantly different from zero ( t -test, a 5 0.05; Zar 1999). Data collected at 10 u C, 17 u C, and 20 u C were tested against the predicted value from the 15 u C regression equation to determine if temperature had a significant effect on coccolith morphology ( t -test, a 5 0.01 after Bonferroni correction; Sokal and Rohlf 1995; Zar ...

Citations

... In particular, the morphology of the intricate, individual calcite plates (coccoliths) that form a cell covering (the coccosphere) of coccolithophores have been shown to respond to a range of environmental perturbations in laboratory studies, including temperature [5][6][7][8][9], nutrient limitation [10][11][12], light intensity [11,12], carbonate chemistry [7, [12][13][14][15], trace metals [12], and salinity [6, [16][17][18][19][20]. Plankton populations and fossil assemblages also show variability in coccolith morphology and size spatially and on seasonal to geological timescales that have been linked to changing ocean conditions, e.g., [21][22][23][24][25][26][27][28]. ...
... Such marginal/coastal systems and semienclosed basins commonly feature strong spatial salinity gradients and may experience more pronounced changes in mean and short-term salinity extremes over the coming century relative to open-ocean settings, as their evaporation-precipitation balance is particularly sensitive to the shorter-term hydrological cycle fluctuations that are likely to be amplified with climate change. Variations in E. huxleyi coccoliths observed along salinity gradients in sediment core top and plankton samples [16,40] and in culture [6, [17][18][19][20] is of particular interest for investigating the productivity and carbonate production responses of past Emiliania populations to regional salinity changes (potentially over the last~270 kyrs since its first occurrence [41,42]). Shifts in coccolith morphology (notably coccolith size) are also a useful contribution to the paleoceanographic toolkit for paleosalinity reconstructions. ...
... 45. Note that the highest salinity treatment in Fielding et al. [19] was 41 rather than 45. Other experimental conditions (temperature, light level and day length, seawater composition etc.) were variable from study to study and all published studies included a period of acclimation before the start of the experiments. ...
Article
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The future physiology of marine phytoplankton will be impacted by a range of changes in global ocean conditions, including salinity regimes that vary spatially and on a range of short- to geological timescales. Coccolithophores have global ecological and biogeochemical significance as the most important calcifying marine phytoplankton group. Previous research has shown that the morphology of their exoskeletal calcified plates (coccoliths) responds to changing salinity in the most abundant coccolithophore species, Emiliania huxleyi. However, the extent to which these responses may be strain-specific is not well established. Here we investigated the growth response of six strains of E. huxleyi under low (ca. 25) and high (ca. 45) salinity batch culture conditions and found substantial variability in the magnitude and direction of response to salinity change across strains. Growth rates declined under low and high salinity conditions in four of the six strains but increased under both low and high salinity in strain RCC1232 and were higher under low salinity and lower under high salinity in strain PLYB11. When detailed changes in coccolith and coccosphere size were quantified in two of these strains that were isolated from contrasting salinity regimes (coastal Norwegian low salinity of ca. 30 and Mediterranean high salinity of ca. 37), the Norwegian strain showed an average 26% larger mean coccolith size at high salinities compared to low salinities. In contrast, coccolith size in the Mediterranean strain showed a smaller size trend (11% increase) but severely impeded coccolith formation in the low salinity treatment. Coccosphere size similarly increased with salinity in the Norwegian strain but this trend was not observed in the Mediterranean strain. Coccolith size changes with salinity compiled for other strains also show variability, strongly suggesting that the effect of salinity change on coccolithophore morphology is likely to be strain specific. We propose that physiological adaptation to local conditions, in particular strategies for plasticity under stress, has an important role in determining ecotype responses to salinity.
... While some E. huxleyi strains can survive at a salinity as low as 15 (Brand, 1984), its calcification is strongly depressed under such conditions, with malformed coccoliths (Saruwatari et al., 2016). Observations from sediment cores also showed that coccolith morphology was dependent on salinity (Fielding et al., 2009), and salinity can affect the hydrogen isotopic composition of long chain alkenones synthesized by E. huxleyi (Schouten et al., 2006). Reduction of salinity led to a smaller cellular volume in E. huxleyi due to reduced thickness of coccoliths (Green et al., 1998;Saruwatari et al., 2016). ...
Article
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While seawater acidification induced by elevated CO2 is known to impact coccolithophores, the effects in combination with decreased salinity caused by sea ice melting and/or hydrological events have not been documented. Here we show the combined effects of seawater acidification and reduced salinity on growth, photosynthesis and calcification of Emiliania huxleyi grown at 2 CO2 concentrations (low CO2 LC:400 μatm; high CO2 HC:1000 μatm) and 3 levels of salinity (25, 30, and 35‰). A decrease of salinity from 35 to 25‰ increased growth rate, cell size and photosynthetic performance under both LC and HC. Calcification rates were relatively insensitive to salinity though they were higher in the LC-grown compared to the HC-grown cells at 25‰ salinity, with insignificant differences under 30 and 35‰. Since salinity and OA treatments did not show interactive effects on calcification, changes in calcification:photosynthesis ratios are attributed to the elevated photosynthetic rates at lower salinities, with higher ratios of calcification to photosynthesis in the cells grown under 35‰ compared with those grown at 25‰. In contrast, photosynthetic carbon fixation increased almost linearly with decreasing salinity, regardless of the pCO2 treatments. When subjected to short-term exposure to high light, the low-salinity-grown cells showed the highest photochemical effective quantum yield with the highest repair rate, though the HC treatment enhanced the PSII damage rate. Our results suggest that, irrespective of pCO2, at low salinity Emiliania huxleyi up-regulates its photosynthetic performance which, despite a relatively insensitive calcification response, may help it better adapt to future ocean global environmental changes, including ocean acidification, especially in the coastal areas of high latitudes.
... Changing environmental conditions can regulate the fraction of cellular energy dedicated to calcification in E. huxleyi 30,41,101,[104][105][106][107][108] . As a matter of fact, a previous study 41 demonstrated that optimum growth, calcification and carbon fixation rates in coccolithophores can occur at different seawater CO 2 concentrations depending on the environmental temperature. ...
Article
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Mesocosm experiments have been fundamental to investigate the effects of elevated CO2 and ocean acidification (OA) on planktic communities. However, few of these experiments have been conducted using naturally nutrient-limited waters and/or considering the combined effects of OA and ocean warming (OW). Coccolithophores are a group of calcifying phytoplankton that can reach high abundances in the Mediterranean Sea, and whose responses to OA are modulated by temperature and nutrients. We present the results of the first land-based mesocosm experiment testing the effects of combined OA and OW on an oligotrophic Eastern Mediterranean coccolithophore community. Coccolithophore cell abundance drastically decreased under OW and combined OA and OW (greenhouse, GH) conditions. Emiliania huxleyi calcite mass decreased consistently only in the GH treatment; moreover, anomalous calcifications (i.e. coccolith malformations) were particularly common in the perturbed treatments, especially under OA. Overall, these data suggest that the projected increase in sea surface temperatures, including marine heatwaves, will cause rapid changes in Eastern Mediterranean coccolithophore communities, and that these effects will be exacerbated by OA.
... To achieve this, strains of the two species Emiliania huxleyi and Gephyrocapsa oceanica were grown under different salinity conditions, as salinity is known to affect E. huxleyi coccolith length (e.g. [34][35][36][37][38][39]). By measuring coccolith thickness with increasing coccolith length, the relationship between coccolith length and thickness in E. huxleyi and G. oceanica could be investigated and the usefulness of the k s model for estimating the mass of these two species evaluated. ...
... The salinity effect on E. huxleyi coccolith length is well documented from both culture, plankton, and sediment studies [34][35][36][37][38][39]. In this study, salinity also affected coccolith length in the E. huxleyi strains RCC 868, RCC 1210, RCC 1824, and SAG 33.90. ...
... Several different morphotypes are described for E. huxleyi, potentially representing separate genotypes [56][57][58][59]. This study only analysed E. huxleyi Type A, and [35] and [38] also focused on Type A in their investigation of coccolith length under different salinities. [39], however, reported changing coccolith length with changing salinity in a strain of E. huxleyi they identified as Type B/C, suggesting that the coccolith length response to changing salinity is consistent between morphotypes. ...
Article
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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.
... Their plankton-derived multiple regression models for in situ salinity varied from that of the previous studies of the Holocene sediment samples. Similar culture-based experiments were carried out to assess applicability of E. huxleyi coccolith morphology as a palaeosalinity proxy 60 . The relationship between the salinity and the morphological response is vaguely understood but probably is related to the regulation of turgor pressure which affects the size of the cell 63 and thus the size of a single coccolith. ...
Article
Coccolithophores are one of the major groups of marine carbonate producers and are the most important pelagic unicellular calcifying organisms those play a pivotal role in the marine biogeochemical cycles. Since past few decades coccolithophores have gained immense attention due to their unique role in the global carbon cycle and particularly due to their combined effects on the biological carbon and carbonate counter pumps. Owing to their high diversity, better preservation, fast turnover rate and significant role in the marine biogeochemical cycles, coccolithophores are identified as a potential proxy to reconstruct paleoceanographic changes. In this review, a broad introduction of the biology and biogeography of extant coccolithophores is discussed by brief overview on the preservation of the coccoliths and their applications. This includes how coccolith abundance, diversity and morphometric studies are used to reconstruct paleotemperature, paleosalinity, paleoproductivity and paleocirculation. In addition, implications of coccolithophores in isotopic studies for the estimation of paleotemperature and paleoproductivity are also discussed.
... Except for Sal29, a salinity at which no growth was achieved by G. oceanica in our batches, our data for this species, and for G. ericsonii, are consistent with this overarching observation that the cells exhibit diminished growth rate with increasing salinity (Figs. 2 and 7). However, the salinity effect on growth rate for the two strains of E. huxleyi (RCC1212 and RCC1256) being examined here markedly differs from observations made by Fisher and Honjo (1989) and Schouten et al. (2006) (strains MHC1 & G4 and PML B92/1, respectively), but are in line with those made on strain PLY B92/11 by Fielding et al. (2009). An optimum in division rates at salinity around 33 (the mean oceanic value and the salinity at which the strains have been maintained in culture for many years) is evident in our data for E. huxleyi Morphotypes A and B. The reason(s) behind this discrepancy are not straightforward to discuss beyond methodology, and may pertain to physiological differences and distinct adaptabilities to changing environment of the multiple ecotypes of E. huxleyi (e.g. ...
Article
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Reconstruction of sea surface temperatures from the oxygen isotope composition (δ¹⁸O) of calcite biominerals synthesised in the mesopelagic zone of the oceans requires knowledge of the δ¹⁸O of seawater and constraints on the magnitude of biological ¹⁸O∕¹⁶O fractionation (the so-called vital effect). In the palaeoceanography community, seawater δ¹⁸O and salinity are unduly treated as a common parameter owing to their strong covariation both geographically and in the geological register. If the former parameter has arguably no notable influence on the biogeochemistry of marine calcifiers, salinity potentially does. However, how salinity per se and the effect of osmotic adjustment can modulate the biogeochemistry, and in turn, the expression of the vital effect in calcite biomineral such as the coccoliths remains undocumented. In this culture-based study of coccolithophores (Haptophyta) belonging to the Noelaerhabdaceae family, we kept temperature and seawater δ¹⁸O constant, and measured basic physiological parameters (growth rate and cell size), and the isotope composition (¹⁸O∕¹⁶O and ¹³C∕¹²C) of coccoliths grown under a range of salinity, between 29 and 39. Ultimately, the overarching aim of this biogeochemical study is to refine the accuracy of palaeotemperature estimates using fossil coccoliths. We found that despite significant physiological changes in the coccolithophores, varying salinity does not modulate biological fractionation of oxygen isotopes. This observation contrasts with previous in vitro manipulations of temperature and carbonate chemistry that led to substantial changes in the expression of the vital effect. As such, salinity does not affect temperature estimation from coccolith-bearing pelagic sequences deposited during periods of change in ice volume, especially at the highest latitudes, or in coastal regions. By contrast, the carbon isotope composition of the coccoliths is influenced by a growth rate mediated control of salinity with implications for deriving productivity indices from pelagic carbonate.
... In support of this hypothesis, we report the occurrence of seasonal unimodal patterns of calcification in the Aegean Sea [46] and of occasional 'mixed' coccospheres, composed of multiple calcification varieties, retrieved along our Mediterranean transect (S3 Fig) and in the Atlantic Ocean [38]. Furthermore, laboratory experiments have demonstrated that the calcification process in E. huxleyi can be strongly influenced by carbonate chemistry [8], salinity [24, [72][73][74], temperature [22,75] and nutrient concentrations [23]: the environmental conditions regulate the cellular energetic consumption dedicated to the calcification process. A complication is that, in laboratory and field studies, two different concepts of 'calcification' are used: calcification rate and calcification degree. ...
Article
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To understand the response of marine calcifying organisms under high CO2 scenarios, it is critical to study their calcification patterns in the natural environment. This paper focuses on a major calcifying phytoplankton group, the coccolithophores, through the analysis of water samples collected along a WE Mediterranean transect during two research cruises, in April 2011 (Meteor cruise M84/3) and May 2013 (MedSeA cruise 2013). The Mediterranean Sea is a marginal sea characterized by large biogeochemical gradients. Currently, it is undergoing both warming and ocean acidification, processes which are rapidly modifying species distribution and calcification. The species Emiliania huxleyi largely dominates the total coc-colithophore production in present day oceans and marine basins, including the Mediterra-nean Sea. A series of morphometric measurements were performed on the coccoliths of this species to estimate their mass, length and calculate a calcification index (proxy for the size-normalized calcification degree). The most abundant morphotype of E. huxleyi in the Mediterranean Sea is Type A. Coccoliths of this morphotype were additionally analyzed based on scanning electron microscopy images: four calcification varieties were quantified, according to the relationship between slit length-tube width, and the state of the central area (open or closed). The average E. huxleyi coccolith mass along the Mediterranean oceanographic transect depended strongly on both the average coccolith length and calcification index. The variability in average coccolith length and calcification index across samples reflected oscillations in the relative abundance of the calcification varieties. We also demonstrated that the distribution of the calcification varieties followed the main environmental gradients (carbonate chemistry, salinity, temperature, nutrient concentrations). Hence, shifts in the distribution of the calcification varieties and of the average E. huxleyi coccolith mass are to be expected in the Mediterranean Sea under climate change. These physiological and ecological responses will modulate the net coccolithophore calcification and, ultimately, the regional carbonate export to the seafloor.
... Other environmental variables have been described as factors influencing calcification in laboratory experiments (Båtvik et al., 1997;Bollmann et al., 2009;Fielding et al., 2009;De Bodt et al., 2010). Although temperature was not completely discarded by Smith et al. (2012), no statistical relationship with coccolith morphometrics was obtained. ...
Article
Abstract Lack of information about carbonate chemistry in inshore waters is a ‘knowledge gap’ in assessing the impacts of changing carbonate chemistry on the marine environment. Assessing the response of calcifying phytoplankton to this changing carbonate chemistry requires a greater understanding of temporal variation. This study provides a description of the variability of carbonate parameters at a monitoring site in the eastern coast of Scotland. Four-years of monthly data were analysed to assess the diversity, abundance and morphometrics of coccolithophores in relation to carbonate chemistry and environmental variables. The seasonality in carbonate parameters reflected the seasonal cycle in phytoplankton activity, with higher total alkalinity concentrations and pH and lower dissolved inorganic carbon concentrations during the growing season. The dominant coccolithophore at the site was Emiliania huxleyi which showed a clear seasonal pattern, being more abundant in mid-summer when warmer and nutrient-depleted conditions restricted the annual diatom bloom. This study revealed the presence of three morphotypes of E. huxleyi, type A, type A overcalcified (type AO) and type B, which were seasonally distributed throughout the year. The less calcified form was mainly observed in spring while heavily calcified morphotypes overlapped during summer. Autumn and winter months were dominated by the most calcified form (type AO). These results indicate that the seasonal pattern of E. huxleyi morphotypes was not related to the carbonate concentration at the site. This study reflects the strong interannual variability in carbonate chemistry and the complexity associated with coccolithophore calcification, and highlights the need of long-term data to understand the potential impact of ocean acidification on calcifying phytoplankton.
... Letelier et al. (2009) and Dávila et al. (2002) reported a seaward-flowing, lowsalinity tongue originating from rivers during high rainfall, matching our observations. However, it seems that, in general, salinity is not a major factor determining the distribution and abundance of coccolithophores (Andruleit et al., 2003;Beaufort et al., 2008), rather it has been linked to an increase in size and more calcification of plates (Paasche et al., 1996;Fielding et al., 2009). However, we found over-calcified specimens of E. huxleyi type A (robust coccoliths,~4-6 µm in diameter) mainly in the area around Z 2 -CUF and the coastal Z 1 stations. ...
... This was also noted in mesocosm experiments in which E. huxleyi coccoliths were more calcified in waters rich in P and N (Beaufort et al., 2007). Other variables reported in the literature that may significantly affect the state of calcification in E. huxleyi are light levels (Balch and Kilpatrick, 1996;Zondervan, 2007), changes in carbonate chemistry (DIC, pH) of upwelling regions (Cubillos et al., 2007) and the possible effect of salinity on size, morphology and the number of coccoliths (Fielding et al., 2009). Although E. huxleyi is the most studied coccolithophore species, substantial gaps remain in our knowledge of its ecophysiological plasticity (Henderiks et al., 2011) and the effects of environmental variables on the production of plates. ...
Article
The role of coccolithophores in the biogenic carbonate cycle was studied in the coastal upwelling zone off Concepción, Chile (36°S), and in adjacent oceanic waters during spring 2004. Coccolithophore abundance and diversity increased steadily from coastal to oceanic regions. The presence of an active coastal upwelling center clearly partitioned the study area into coastal, transition and two oceanic zones. Coccolithophores and diatoms showed an inverse relationship: coccolithophores with higher abundances in oceanic zones and diatoms more abundant in coastal zones. The suspended coccolithophore carbonate reached maximum values in the oceanic zones. Emiliania huxleyi was the only coccolithophore species observed in the coastal, upwelling-influenced region. The vertical export of coccolithophore carbonate offshore from Concepción (traps deployed between December 2005 and October 2006) was highly variable, with greatest flux during summer, dominated by coccoliths and coccospheres of large species: Calcidiscus leptoporus and Helicosphaera carteri. The contribution of coccoliths and coccospheres carried downward in appendicularian fecal pellets to total carbonate flux was low (1%); however, they contributed a major fraction to the coccolithophore carbonate export (mean of 27%). Our results highlight the relevance of large and less abundant coccolithophores and their coccoliths to the vertical flux of coccolithophore carbonate to the deep sea.
... The relationships between coccolith size and various environmental factors, such as growth phase, temperature, salinity, and nutrients, have been investigated using E. huxleyi cultures (e.g., Watabe and Wilbur, 1966;Young and Westbroek, 1991;Paasche, 2001;Fielding et al., 2009). Young and Westbroek (1991) investigated the size of coccolith at the end of growth phase, resulting that Type A coccolith is normally smaller than Type B coccolith. ...
... Regarding the effects of salinity, Paasche et al. (1996) first reported that lower salinity was associated with a decrease in the length of the distal and proximal shield elements. Fielding et al. (2009) reported a linear correlation between salinity and the length of the distal shield. Phosphorous deficiency may induce overcalcification, while nitrogen limitation may result in the production of less-calcified coccoliths (Paasche, 1998). ...
... Growth rate increased as salinity decreased from 32 to 26 ‰, which is in part consistent with Passche et al. (1996); however, the growth rates in this study (0.6-0.53 d −1 ) were markedly lower than those reported by Passche. On the other hand, Fielding et al. (2009) reported an increase in growth rate from 0.05 to 0.7 d −1 with increasing salinity. The lower growth rate in their study might have been caused by use of a lower light intensity than that used by Passche et al. (1996). ...
Article
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Strains of the coccolithophore Emiliania huxleyi (Haptophyta) collected from the subarctic North Pacific and Arctic oceans in 2010 were established as clone cultures and have been maintained in the laboratory at 15 °C and 32 ‰ salinity. To study the physiological responses of coccolith formation to changes in temperature and salinity, growth experiments and morphometric investigations were performed on two strains, namely MR57N isolated from the northern Bering Sea and MR70N at the Chukchi Sea. This is the first report of a detailed morphometric and morphological investigation of Arctic Ocean coccolithophore strains. The specific growth rates at the logarithmic growth phases in both strains markedly increased as temperature was elevated from 5 to 20 °C, although coccolith productivity (estimated as the percentage of calcified cells) was similar at 10–20 % at all temperatures. On the other hand, the specific growth rate of MR70N was affected less by changes in salinity in the range 26–35 ‰, but the proportion of calcified cells decreased at high and low salinities. According to scanning electron microscopy (SEM) observations, coccolith morphotypes can be categorized into Type B/C on the basis of their biometrical parameters. The central area elements of coccoliths varied from thin lath type to well-calcified lath type when temperature was increased or salinity was decreased, and coccolith size decreased simultaneously. Coccolithophore cell size also decreased with increasing temperature, although the variation in cell size was slightly greater at the lower salinity level. This indicates that subarctic and arctic coccolithophore strains can survive in a wide range of seawater temperatures and at lower salinities with change in their morphology. Because all coccolith biometric parameters followed the scaling law, the decrease in coccolith size was caused simply by the reduced calcification. Taken together, our results suggest that calcification productivity may be used to predict future oceanic environmental conditions in the polar regions.