Assessing the applicability of Emiliania huxleyi coccolith morphology as a sea‐surface salinity proxy
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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. Using regression analysis, the effect of salinity on coccolith morphology was compared to those previously observed in sediment core‐top and plankton data. No significant differences were found between the slopes of these data, suggesting that salinity is the primary control on E. huxleyi coccolith size and element number in the ocean. However, the intercepts of the culture data were significantly higher. A combination of experimental and literature analysis indicated that temperature and nutrients were unlikely to be the causes of this discrepancy. Literature analysis also highlighted that coccolith size data from marginal environments displayed different intercepts to those from the open‐ocean data. This suggests that discrete morphotypes exist in these marginal locations. We, therefore, recommend that the original E. huxleyi coccolith morphology palaeo‐SSS transfer function requires further evaluation before being routinely applied.Keywords:
Coccolith
Emiliania huxleyi
Coccolithophore
paleoceanography
Abstract. Strains of the coccolithophore Emiliania huxleyi (Haptophyta) collected from the subarctic North Pacific and Arctic Oceans during the R/V MIRAI cruise in 2010 (MR10-05) 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 of MR57N isolated from the northern Bering Sea (56°58' N, 167°11' W) and MR70N at the Chukchi Sea (69°99' N, 168° W). 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 (the percentage of calcified cells) was similar at 10–20 % at all temperatures. On the other hand, the specific growth rate of strain 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, such as length of the distal shield (LDS), length of the inner central area (LICA), and the thickness of distal shield elements. The central area elements of coccoliths varied from grilled type to closed 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 due to their marked morphometric adaptation ability. 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.
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Emiliania huxleyi
Coccolith
Temperature salinity diagrams
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Abstract. Within the context of the UK Ocean Acidification project, Emiliania huxleyi (type A) coccolith morphology was examined from samples collected during cruise D366. In particular, a morphometric study of coccolith size and degree of calcification was made on scanning electron microscope images of samples from shipboard CO2 perturbation experiments and from a set of environmental samples with significant variation in calcite saturation state (Ωcalcite). One bioassay in particular (E4 from the southern North Sea) yielded unambiguous results – in this bioassay exponential growth from a low initial cell density occurred with no nutrient enrichment and coccosphere numbers increased tenfold during the experiment. The samples with elevated CO2 saw significantly reduced coccolithophore growth. However, coccolithophore morphology was not significantly affected by the changing CO2 conditions even under the highest levels of perturbation (1000 μatm CO2). Environmental samples similarly showed no correlation of coccolithophore morphology with calcite saturation state. Some variation in coccolith size and degree of calcification does occur but this seems to be predominantly due to genotypic differentiation between populations on the shelf and in the open ocean.
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Emiliania huxleyi
Ocean Acidification
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Morphology
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The coccolithophore Emiliania huxleyi (Lohm.) Hay and Mohler is one of the most abundant calcite producing organisms on earth, producing calcium carbonate plates known as coccoliths. Consequently, these coccoliths represent a major carbon sink in the world ocean. This study addresses the rate of detachment of coccoliths from coccolithophores under controlled growth conditions using light-limited continuous cultures. Cells were grown at six different growth rates between 0.24 day−1 and 1.00 day−1. Other cell properties including chlorophyll, particulate inorganic carbon, and total particulate carbon, were also investigated with regard to growth rate of the cells. The coccolith detachment rate increased linearly with cellular growth rate at a ratio not significantly different from 1.00. This change in detachment with growth could affect several processes such as sinking rates of cells and the appearance of blooms in remotely-sensed imagery. The importance of sinking to coccolithophores is discussed.
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Cell geometry and size strongly determine the physiology of unicellular algae, exerting specific control on isotopic and elemental discrimination during photosynthesis and biomineralisation. In recent years, coccolithophore-derived paleoceanographic proxies have contributed to a better understanding of past variability in sea surface temperature and growth rates of ancient haptophytes, as well as past levels of atmospheric carbon dioxide. Investigations into the mechanisms underlying these biogeochemical proxies underpin the importance of coccolithophorid cell size. Thus, accurate reconstructions of ancient cell size from the fossil record would improve the interpretations of such paleo-proxies. However, this approach is complicated by the fact that the fossil record of coccolithophores is dominated by single coccoliths, rather than by intact coccospheres, formed by interlocking coccoliths that surround living cells.This paper presents quantitative constraints on coccolith size, coccosphere- and cell diameter, for three main Cenozoic genera of coccolithophore (Reticulofenestra, Cyclicargolithus and Coccolithus) through detailed biometry of rarely fossilized coccospheres. Together, these taxa are most dominant in Cenozoic deep-sea sediments, providing an exquisitely detailed record of their evolution and the bulk of coccolith-carbonate burial through time. Accurate estimates of coccolithophore cell size can be made by relatively simple size measurements of individual coccoliths in fossil assemblages. For the investigated taxa, the number of coccoliths per fossil coccosphere remained relatively constant throughout the Cenozoic, thus offering better control on estimates of cellular calcite production by the ancestors of today’s prolific bloom-forming coccolithophores Emiliania huxleyi, Gephyrocapsa spp. and Coccolithus pelagicus.
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Coccolith
Emiliania huxleyi
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Ocean Acidification
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Emiliania huxleyi
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Coccolith
Ocean Acidification
Total inorganic carbon
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Four strains of the coccolithophore Emiliania huxleyi (RCC1212, RCC1216, RCC1238, RCC1256) were grown in dilute batch culture at four CO 2 levels ranging from ~200 µatm to ~1200 µatm. Coccolith morphology was analyzed based on scanning electron micrographs. Three of the four strains did not exhibit a change in morphol- ogy over the CO 2 range tested. One strain (RCC1256) displayed an increase in the percentage of malformed coccoliths with increasing CO 2 concentration. We conclude that the sensitivity of the coccolith-shaping machinery to carbonate chemistry changes is strain-specific. Although it has been shown before that carbonate chemistry related changes in growth- and calcification rate are strain-specific, there seems to be no consistent correlation between coccolith mor - phology and growth or calcification rate. We did not observe an increase in the percentage of incomplete coccoliths in RCC1256, indicating that the coccolith-shaping machinery per se is affected by acidification and not the signalling pathway that produces the stop-signal for coccolith growth.
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Emiliania huxleyi
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Ocean Acidification
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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.
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Abstract. The Cretaceous ocean witnessed intervals of profound perturbations such as volcanic input of large amounts of CO2, anoxia, eutrophication, and introduction of biologically relevant metals. Some of these extreme events were characterized by size reduction and/or morphological changes of a few calcareous nannofossil species. The correspondence between intervals of high trace metal concentrations and coccolith dwarfism suggests a negative effect of these elements on nannoplankton biocalcification process in past oceans. In order to verify this hypothesis, we explored the potential effect of a mixture of trace metals on growth and morphology of four living coccolithophore species, namely Emiliania huxleyi, Gephyrocapsa oceanica, Pleurochrysis carterae and Coccolithus pelagicus. These taxa are phylogenetically linked to the Mesozoic species showing dwarfism under excess metal concentrations. The trace metals tested were chosen to simulate the environmental stress identified in the geological record and upon known trace metal interaction with living coccolithophores algae. Our laboratory experiments demonstrated that elevated trace metal concentrations not only affect coccolithophore algae production but, similarly to the fossil record, coccolith size and/or weight. Smaller coccoliths were detected in E. huxleyi and C. pelagicus, while coccoliths of G. oceanica showed a decrease in size only at the highest trace metal concentrations. P. carterae coccolith size was unresponsive for changing trace metal amounts. These differences among species allow to discriminate most- (P. carterae), intermediate- (E. huxleyi), and least- (C. pelagicus and G. oceanica) tolerant taxa. The fossil record and the experimental results converge on a selective response of coccolithophores to metal availability. These species-specific differences must be considered before morphological features of coccoliths are used to reconstruct paleo-chemical conditions.
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Ocean Acidification
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Abstract The marine biological calcification and photosynthesis, which can produce particulate inorganic and organic carbon (PIC and POC), have the opposite effects on seawater p CO 2 . Coccolithophores are a kind of marine unicellular algae with both of the two biological processes, and PIC and POC productions of them can shape the water column rain ratio as a dominant driver for Earth's carbon cycle. Thus, the changes in ancient coccolithophore PIC:POC can be important for the paleoceanographic and paleoclimatic studies of carbon cycle modeling. However, ancient coccolithophore PIC:POC is poorly constrained because of the occasional occurrences of intact coccospheres in deep ocean sediments, as detached coccoliths are commonly the remnants of fossilized coccolithophores. Here, we carry out the biometric analysis of coccosphere and coccolith from the living cells of Emiliania huxleyi and Gephyrocapsa oceanica in the South China Sea, and confirm a significant correlationship between their PIC:POC and lateral coccolith aspect ratio ( AR L ). AR L here is defined by the ratio of mean coccolith thickness with respect to coccolith length. A linear regression is given, ( R 2 = 0.59, n = 121), for the reconstruction of ancient Noelaerhabdaceae coccolithophore PIC:POC based on individual coccoliths in marine sediments. Based on this equation, we reconstruct ancient Noelaerhabdaceae coccolithophore PIC:POC since 14 million years ago (Ma) using published coccolith data, which reveal a long‐term decrease in PIC:POC from 7 to 4 Ma. We suggest that such a change in coccolithophore physiology may be induced by a simultaneous long‐term decline in seawater calcium concentration.
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Emiliania huxleyi
paleoceanography
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Abstract Coccolithophores are a key functional phytoplankton group and produce minute calcite plates (coccoliths) in the sunlit layer of the pelagic ocean. Coccoliths significantly contribute to the sediment record since the Triassic and their geometry have been subject to palaeoceanographic and biological studies to retrieve information on past environmental conditions. Here, we present a comprehensive analysis of coccolith, coccosphere and cell volume data of the Southern Ocean Emiliania huxleyi ecotype A, subject to gradients of temperature, irradiance, carbonate chemistry and macronutrient limitation. All tested environmental drivers significantly affect coccosphere, coccolith and cell volume with driver‐specific sensitivities. However, a highly significant correlation emerged between cell and coccolith volume with V coccolith = 0.012 ± 0.001 * V cell + 0.234 ± 0.066 (n = 23, r 2 = .85, p < .0001, σ est = 0.127), indicating a primary control of coccolith volume by physiological modulated changes in cell volume. We discuss the possible application of fossil coccolith volume as an indicator for cell volume/size and growth rate and, additionally, illustrate that macronutrient limitation of phosphorus and nitrogen has the predominant influence on coccolith volume in respect to other environmental drivers. Our results provide a solid basis for the application of coccolith volume and geometry as a palaeo‐proxy and shed light on the underlying physiological reasons, offering a valuable tool to investigate the fossil record of the coccolithophore E. huxleyi .
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Emiliania huxleyi
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Ocean Acidification
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