DISTRIBUTION OF TWO TYPES OF EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE) IN THE NORTHEAST ATLANTIC REGION AS DETERMINED BY IMMUNOFLUORESCENCE AND COCCOLITH MORPHOLOGY1

Culture strains of Emiliania huxleyi (Lohmann 1902) Hay et al. 1967 were placed into two groups designated E. huxleyi type A and type B on the basis of coccolith morphology and immunological properties of the coccolith polysaccharide. We studied the distribution of these types in the North Atlantic region using an indirect immunofluorescence assay with antisera directed against the coccolith polysaccharide of E. huxleyi type A and type B and epifluorescence microscopy. In field samples taken in the Northeast Atlantic Ocean, E. huxleyi type A was found exclusively. In contrast, type B was dominant in the North Sea. Scanning electron microscopy of the samples revealed the same unequal distribution of the two types as found with the immunofluorescent-labelling assay.     

Increased CO<Subscript>2</Subscript> and the effect of pH on growth and calcification of <Emphasis Type="Italic">Pleurochrysis carterae</Emphasis> and <Emphasis Type="Italic">Emiliania huxleyi</Emphasis> (Haptophyta) in semicontinuous cultures

The effects of changes in CO₂ and pH on biomass productivity and carbon uptake of Pleurochrysis carterae and Emiliania huxleyi in open raceway ponds and a plate photobioreactor were studied. The pH of P. carterae cultures increased during day and decreased at night, whereas the pH of E. huxleyi cultures showed no significant diurnal changes. P. carterae coccolith production occurs during the dark period, whereas in E. huxleyi, coccolith production is mainly during the day. Addition of CO₂ at constant pH (pH-stat) resulted in an increase in P. carterae biomass and coccolith productivity, while CO₂ addition lowered E. huxleyi biomass and coccolith production. Neither of these algae could grow at less than pH 7.5. Species-specific diurnal pH and pCO₂ variations could be indicative of significant differences in carbon uptake between these two species. While E. huxleyi has been suggested to be predominantly a bicarbonate user, our results indicate that P. carterae may be using CO₂ as the main C source for photosynthesis and calcification.     

Seasonal occurrence of coccoliths in sediment traps from West Caroline Basin, equatorial West Pacific Ocean

Coccolith fluxes were investigated by sediment trap studies in the West Caroline Basin, which is located in the equatorial western Pacific. The investigation was conducted from June 1991 to March 1992 at two water depths, 1592 and 3902 m, as part of the Northwest Pacific Carbon Cycle Study (NOPACCS) program. Two seasonal maxima of coccolith fluxes were observed during September–early October and late December–January. The average coccolith and coccosphere fluxes at the depth of the shallow trap were 1800×10⁶ coccoliths m⁻² day⁻¹ and 1.9×10⁶ coccospheres m⁻² day⁻¹, respectively. The flux of coccoliths followed the same trend as the total flux, and was closely correlated with the flux of organic matter flux. Florisphaera profunda, Gladiolithus flabellatus, Gephyrocapsa oceanica, Umbilicosphaera sibogae var. sibogae, Emiliania huxleyi, and Oolithotus fragilis were the most abundant species together comprising more than 85% of the total flora. Observed seasonal changes of the species composition of coccolith flora, as well as analysis of the R-mode cluster, revealed that during the summer, the assemblage was marked by the dominance of G. oceanica and U. sibogae. However, during the winter, the assemblage was dominated by E. huxleyi and O. fragilis. These assemblage changes were influenced by monsoonal events, which were observed off the New Guinea coast. F. profunda dominated the community in the shallow trap throughout most of the year; peak values of this species were recorded during the winter. The coccosphere assemblage was dominated by G. oceanica at both water depths. In the deep trap, the sedimentation pattern was similar to that observed at the shallow depth. Mean coccolith and coccosphere fluxes at the deep trap were 2000×10⁶ coccolith m⁻² day⁻¹ and 0.08×10⁶ coccospheres m⁻² day⁻¹, respectively. The increase in coccolith flux with water depth suggests a lateral influx. The estimated average daily mass of CaCO₃ flux in coccoliths and coccospheres was 16.6 mg m⁻² day⁻¹ at the 1592 m trap and 17.9 mg m⁻² day⁻¹ at the 3902 m trap, respectively. These calculated values contributed only 23.3% to the total CaCO₃ flux at the shallow trap and 27.9% at the deep trap.     

Calcareous nannoplankton in surface sediments of the East China Sea

Twenty-eight species of coccoliths were identified in surface sediments of the East China Sea. The species composition of the coccolith assemblages is similar to that of the North Pacific Water Mass, but differs from the latter by a greater dominance ofEmiliania huxleyi andGephyrocapsa oceanica (together making up over 90% specimens). The coccolith species composition shows considerable differences between the continental shelf and the Okinawa Trough areas, reflecting different water masses. On the other hand, the coccolith content in sediments is apparently controlled largely by the deposition rate of terrigenous material.     

Biometry of Upper Cretaceous (Cenomanian–Maastrichtian) coccoliths – a record of long-term stability and interspecies size shifts

Biometric measurements of Mesozoic coccoliths (coccolith length and width) have been used in short-term biostratigraphic, taxonomic and palaeoecologic studies, but until now, not over longer time scales. Here, we present a long time-series study (∼ 30 million years) for the Upper Cretaceous, which aims to identify broad trends in coccolith size and to understand the factors governing coccolith size change over long time scales. We have generated biometric data for the dominant Upper Cretaceous coccolith groups, Broinsonia/Arkhangelskiella, Prediscosphaera, Retecapsa and Watznaueria, from 36 Cenomanian–Maastrichtian (100.5–66 Ma) samples from Goban Spur in the northeast Atlantic (DSDP Site 549). These data show that the coccolith sizes within Prediscosphaera, Retecapsa and Watznaueria were relatively stable through the Late Cretaceous, with mean size variation less than 0.7 μm. Within the Broinsonia/Arkhangelskiella group there was more pronounced variation, with a mean size increase from ∼ 6 μm in the Cenomanian to ∼ 10 μm in the Campanian. This significant change in mean size was largely driven by evolutionary turnover (species origination and extinctions), and, in particular, the appearance of larger species/subspecies (Broinsonia parca parca, Broinsonia parca constricta, Arkhangelskiella cymbiformis) in the early Campanian, replacing smaller species, such as Broinsonia signata and Broinsonia enormis. Shorter-term size fluctuations within Broinsonia/Arkhangelskiella, observed across the Late Cenomanian–Turonian and Late Campanian–Maastrichtian intervals, may, however, reflect changing palaeoenvironmental conditions, such as sea surface temperature and nutrient availability.     

Strontium/Calcium ratio, carbon and oxygen stable isotopes in coccolith carbonate from different grain-size fractions in South Atlantic surface sediments

In this study, the Strontium/Calcium (Sr/Ca) ratio, and the carbon and oxygen isotopic compositions of coccoliths are investigated in three different grain-size fractions (<20 μm, 15-5 μm, <5 μm) of 17 surface sediment samples from the Equatorial and South Atlantic. The results are compared to environmental parameters in order to assess the factors controlling the observed coccolith geochemical patterns. Isotopic and geochemical composition of coccolith species in surface sediment samples from the South Atlantic greatly varies according to the different grain-size fractions. However, even if the absolute values show a great offset, the general trends are comparable. The δ¹⁸O values show a decreasing trend with increasing temperature. The δ¹³C and Sr/Ca ratio are mainly influenced by productivity of coccolithophores, which is in turn controlled by different factors, such as temperature, nutrient supply and productivity of other phytoplankton groups. Dilution and dissolution are negligible factors in these open marine samples. Therefore, coccolith abundance in bulk sediment is the best approximation for productivity of coccolithophores. The various coccolith species fractionate Sr differently, as is best shown by the 5-15 μm fraction where three species (Calcidiscus leptoporus, Helicosphaera carteri and Coccolithus pelagicus) predominantly occur.     

Difference in physiological responses of growth,photosynthesis and calcification of the coccolithophore Emiliania huxleyi to acidification by acid and CO2 enrichment

Ocean acidification, one of the great global environmental issues at present, is expected to result in serious damage on marine calcareous organisms such as corals and calcifying algae, which potentially release huge amounts of CO₂ from the ocean to the atmosphere. The coccolithophore, Emiliania huxleyi (Haptophyceae), which frequently produces blooms, has greatly contributed to the biological CO₂ pump. This study was aimed at analyzing effects of how E. huxleyi responds to acidification. Acidification was performed by two methods, namely by just adding HCl under bubbling ordinary air at 8.2–8.4, 7.6–7.8 and 7.1–7.3 (acidification by HCl) and by bubbling with ordinary air or with increased CO₂ concentration such as 406, 816 and 1,192 ppm that maintained pH of the medium at 8.0–8.3, 7.6–7.9 and 7.5–7.7 (acidification by CO₂ enrichment). As a result, cell growth and cellular calcification of E. huxleyi were strongly damaged by acidification by HCl, but not by acidification by CO₂ enrichment. The activities of photosystems such as F _v/F _m and ?PSII were not affected by any acidification conditions while photosynthetic O₂ evolution was slightly stimulated. A ⁴⁵Ca-radiotracer experiment revealed that Ca²⁺-uptake was strongly suppressed by acidification with HCl. This suppression recovered after increasing the dissolved inorganic carbon (DIC) concentration and further stimulated by an additional increase in DIC concentration. The production of storage and coccolith polysaccharides was increased by acidification by HCl and also highly stimulated by acidification with CO₂ enrichment. The present study clearly showed that the coccolithophore, E. huxleyi, has an ability to respond positively to acidification with CO₂ enrichment, but not just acidification.     

Stable isotope fractionation of strontium in coccolithophore calcite: Influence of temperature and carbonate chemistry

Marine calcifying eukaryotic phytoplankton (coccolithophores) is a major contributor to the pelagic production of CaCO₃ and plays an important role in the biogeochemical cycles of C, Ca and other divalent cations present in the crystal structure of calcite. The geochemical signature of coccolithophore calcite is used as palaeoproxy to reconstruct past environmental conditions and to understand the underlying physiological mechanisms (vital effects) and precipitation kinetics. Here, we present the stable Sr isotope fractionation between seawater and calcite (Δ^88/86Sr) of laboratory cultured coccolithophores in individual dependence of temperature and seawater carbonate chemistry. Coccolithophores were cultured within a temperature and a pCO₂ range from 10 to 25°C and from 175 to 1,240 μatm, respectively. Both environmental drivers induced a significant linear increase in coccolith stable Sr isotope fractionation. The temperature correlation at constant pCO₂ for Emiliania huxleyi and Coccolithus braarudii is expressed as Δ^88/86Sr = ?7.611 × 10^?3 T + 0.0061. The relation of Δ^88/86Sr to pCO₂ was tested in Emiliania huxleyi at 10 and 20°C and resulted in Δ^88/86Sr = ?5.394 × 10^?5 pCO₂ – 0.0920 and Δ^88/86Sr = ?5.742 × 10^?5 pCO₂ – 0.1351, respectively. No consistent relationship was found between coccolith Δ^88/86Sr and cellular physiology impeding a direct application of fossil coccolith Δ^88/86Sr as coccolithophore productivity proxy. An overall significant correlation was detected between the elemental distribution coefficient (D_Sr) and Δ^88/86Sr similar to inorganic calcite with a physiologically induced offset. Our observations indicate (i) that temperature and pCO₂ induce specific effects on coccolith Δ^88/86Sr values and (ii) that strontium elemental ratios and stable isotope fractionation are mainly controlled by precipitation kinetics when embedded into the crystal lattice and subject to vital effects during the transmembrane transport from seawater to the site of calcification. These results provide an important step to develop a coccolith Δ^88/86Sr palaeoproxy complementing the existing toolbox of palaeoceanography.     

Light-dependent coccolith formation in the two forms of Coccolithus pelagicus

Summary Two methods were employed for measuring coccolith formation and photosynthesis in coccolithophorids. The first method was based on measurements of ¹⁴C radioactivity of cells on membrane filters before and after acid treatment. The second method involved a conversion of ¹⁴C in coccoliths or whole cells to BaCO₃ prior to counting. It was observed that in determinations of photosynthetic (or total) ¹⁴C by the first method, the count rate produced by a given amount of the isotope was 30–40% lower in the non-motile and motile forms of Coccolithus pelagicus than in C. huxleyi. There was no similarly great discrepancy in determinations of coccolith ¹⁴C.Light-dependent coccolith formation was demonstrated in both forms of C. pelagicus. The non-motile form may deposit several times more carbon in its coccoliths than it assimilates photosynthetically. In the motile form, coccolith carbon amounts to less than 2% of photosynthetic carbon.     

Export production of coccolithophores in an upwelling region: Results from San Pedro Basin, Southern California Borderlands

A seven month-long time series sediment trap project was carried out in San Pedro Basin (Southern California Borderlands) in order to evaluate the response of calcareous nannoplankton to seasonal hydrographic changes. This region is periodically influenced by upwelling, particularly during the spring and early summer. The highest fluxes of both whole coccospheres and individual coccoliths occurred during winter (January-February), a period when the fluxes of diatoms and planktic foraminifera were low. The highest coccolithophore fluxes were recorded in the mid-February with 860 × 10⁶ coccoliths m⁻² day⁻¹, 8 × 10⁶ whole coccospheres m⁻² day⁻¹, and 80 mg of coccolith carbonate m⁻² day⁻¹. Coccolith carbonate fluxes in January and February account for most of the total carbonate fluxes measured during this period. The season of maximum coccolithophore production in this region (winter) is correlated with weak stratification of the upper water column, low total primary production, low nutrient contents, and low temperatures.Emiliania huxleyi and Florisphaera profunda are the two most abundant species in this region. While E. huxleyi displays no distinct seasonal changes in flux, F. profunda shows a clear preference for cold, low nutrient water conditions and low light levels. Helicosphaera spp. flux is positively correlated to the total coccosphere fluxes and is indicative of high coccolithophore productivity.     

Coccolith volume of the Southern Ocean coccolithophore Emiliania huxleyi as a possible indicator for palaeo‐cell volume

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, r² = .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.     

Seasonal and Spatial Distribution of Vitamin B12 in a Coastal Area of Eastern Mediterranean Sea

The seasonal and spatial distribution of vitamin B₁₂ was investigated in Eastern Mediterranean (Saronicos Gulf, Aegean Sea). Vitamin B₁₂ concentration had an annual range 0.12–7.93 ng. 1⁻¹ and an annual mean 1.88 ng. 1⁻¹. The statistical analysis of data indicated significant seasonal and regional variations of vitamin B₁₂ in this area and an inverse relationship of this vitamin with chl a. The results showed that the Eastern Mediterranean Sea contains less vitamin B₁₂ than the Western Mediterranean Sea.     

COCCOLITH-ASSOCIATED POLYSACCHARIDES FROM CELLS OF EMILIANIA HUXLEYI (HAPTOPHYCEAE)1

Coccoliths of Emiliania huxleyi (Lohmann) Hay and Mohler, a unicellular calcifying alga, consist of calcite closely associated with an acidic, Ca²⁺-binding polysaccharide. This polysaccharide is thought to play a regulatory role in coccolith synthesis by interfering with CaCO₃ crystallization. Here we show that the polysaccharides from three different strains, A 92, L and 92 D, all inhibit the precipitation of CaCO₃ in vitro to the same extent. The monosaccharide compositions of the A 92 and L polysaccharide are similar. The 92 D material, however, deviates from the other two: it contains significantly lower amounts of methylated sugars and ribose, and elevated levels of rhamnose and galactose. It also contains antigenic determinants not detected in the A 92 and L polysaccharides. In contrast to the latter two macromolecules the 92 D polysaccharide migrates as two bands upon polyacrylamide gel electrophoresis, possibly resulting from complexing with small amounts of protein. The coccolith polysaccharide from L cells, cultured at an elevated growth rate, also migrates as two bands. This phenomenon is due to an increase in molecular size distribution. The results suggest that certain properties of the molecule may be subject to variation without interfering with its function.     

Coccolith Sr/Ca ratios in the eastern Mediterranean: Production versus export processes

Samples collected by two sediment traps located southwest of Crete in the eastern Mediterranean (EMED) [48A (1953 m) and 48B (950 m)] from June 2005 to May 2006 were used to study fluxes of organic carbon, carbonate and coccolithophores in combination with the variations of Sr/Ca ratios in different individually picked coccolith species. Considering the complexity of the EMED, we validate the use of Sr/Ca ratios as productivity proxy and unravel the varied processes which may influence it. We examined the relationship between the seasonal peaks in export fluxes and the Sr/Ca ratio in coccoliths of three upper photic zone coccolithophores species collected in the traps, Calcidiscus leptoporus, Helicosphaera carteri and Emiliania huxleyi. We aimed at testing whether high export fluxes are correlated with high Sr/Ca ratios, suggestive of higher nutrient-stimulated production, or Sr/Ca ratios are unchanged during high export periods, suggestive of increased export efficiency or scavenging. Periods of enhanced trap fluxes in March and June result from surface water blooms recognized in satellite imagery. An additional peak flux was found in January, but this peak represents re-suspended or recycled material in the water column.The amplitude of seasonal variations in the Sr/Ca ratios of the three investigated species is small in both traps. In the shallow trap, a decrease in the Sr/Ca ratio of C. leptoporus occurred synchronously with minimal fluxes. The other two species were not measured for this period. In the deep trap, no such decrease in Sr/Ca was observed during minimal fluxes, in either C. leptoporus or H. carteri, probably due to a long residence of coccoliths in the water column, recycling and low export efficiency. Absolute Sr/Ca ratios for all species are lower than in other more productive environments like the Bay of Bengal, Arabian Sea, or Sargasso Sea. We conclude that Sr/Ca ratios in coccoliths of surface sediments in the EMED reflect mainly spring–summer bloom conditions averaged over hundreds to thousands of years.In addition, the origin of varying calcite thickness in H. carteri was investigated. The similarity of average Sr/Ca ratios in differently-calcified specimens confirms that coccolith thickness variations in this species result from primary biomineralization processes and not from variable overgrowth by (low Sr) abiogenic calcite in the water column or the sediments.     

Evolution of the coccolith genus Lotharingius during the Late Pliensbachian-Early Toarcian interval in Asturias (N Spain). Consequences of the Early Toarcian environmental perturbations

The evolution of the coccolith genus Lotharingius was investigated in 18 samples from the West Rodiles section (Asturias, Northern Spain), Upper Pliensbachian-Lower Toarcian in age. In each sample, the length and width of the coccolith and of its central area were measured on 150 specimens of Lotharingius. A total of 2700 specimens were measured, and 10,800 measurements were obtained. Based on the results of the morphometric analysis, the stratigraphic ranges, the abundance patterns and the light microscope observations, the aims of this work are to determine whether the specimens analysed correspond to different species, to distinct ecophenotypes or to an anagenetic lineage of morphotypes of a single species with overlapping stratigraphic ranges, and to test the influence of the paleoenvironmental perturbations during the Early Toarcian on the studied genus. Three species of Lotharingius were distinguished: L. hauffii, L. sigillatus and L. crucicentralis. Based on central area size and structure, two morphotypes (A and B) of L. hauffii were differentiated. All the parameters measured show a great overlap between the morphotypes and species. An increase in both coccolith and central area size and a development of more complex central area structures were observed through the studied section. L. hauffii is the smallest form, followed by L. sigillatus, and finally L. crucicentralis is the largest species and has the most complex central area structure. A clear decrease in size or “dwarfing” of the species was observed in the samples corresponding to the Early Toarcian environmental perturbations. L. crucicentralis was not identified in these samples. We hypothesize that the changes in size and abundance of the Lotharingius species could be related to the unfavourable palaeoenvironmental conditions for the biomineralization of their coccoliths.     

Low Temperature Stimulates Cell Enlargement and Intracellular Calcification of Coccolithophorids

Temperature effect on growth, cell size, calcium uptake activity, coccolith production was studied in coccolith-producing haptophytes, Emiliania huxleyi (Lohmann) Hay & Mohler (strain EH2) and Gephyrocapsa oceanica Kamptner (strain GO1) (Coccolithophorales, Prymnesiophyceae). E. huxleyi grew at a wider temperature range (10°–25°C), while G. oceanica growth was limited to warmer temperatures (20°–25°C). Cell size was inversely correlated with temperature. At low temperature, the enlargement of chloroplasts and cells and the stimulation of coccolith production were morphologically confirmed under fluorescent and polarization microscopes, respectively. ⁴⁵ Ca uptake by E. huxleyi at 10°C was greatly increased after a 5-day lag and exceeded that at 20°C. These results clearly showed that low temperature suppressed coccolithophorid growth but induced cell enlargement and as stimulated the intracellular calcification that produces coccoliths.     

Formation and mosaicity of coccolith segment calcite of the marine algae Emiliania huxleyi

Coccolithophores belong to the most abundant calcium carbonate mineralizing organisms. Coccolithophore biomineralization is a complex and highly regulated process, resulting in a product that strongly differs in its intricate morphology from the abiogenically produced mineral equivalent. Moreover, unlike extracellularly formed biological carbonate hard tissues, coccolith calcite is neither a hybrid composite, nor is it distinguished by a hierarchical microstructure. This is remarkable as the key to optimizing crystalline biomaterials for mechanical strength and toughness lies in the composite nature of the biological hard tissue and the utilization of specific microstructures. To obtain insight into the pathway of biomineralization of Emiliania huxleyi coccoliths, we examine intracrystalline nanostructural features of the coccolith calcite in combination with cell ultrastructural observations related to the formation of the calcite in the coccolith vesicle within the cell. With TEM diffraction and annular dark‐field imaging, we prove the presence of planar imperfections in the calcite crystals such as planar mosaic block boundaries. As only minor misorientations occur, we attribute them to dislocation networks creating small‐angle boundaries. Intracrystalline occluded biopolymers are not observed. Hence, in E. huxleyi calcite mosaicity is not caused by occluded biopolymers, as it is the case in extracellularly formed hard tissues of marine invertebrates, but by planar defects and dislocations which are typical for crystals formed by classical ion‐by‐ion growth mechanisms. Using cryo‐preparation techniques for SEM and TEM, we found that the membrane of the coccolith vesicle and the outer membrane of the nuclear envelope are in tight proximity, with a well‐controlled constant gap of ~4 nm between them. We describe this conspicuous connection as a not yet described interorganelle junction, the “nuclear envelope junction”. The narrow gap of this junction likely facilitates transport of Ca²⁺ ions from the nuclear envelope to the coccolith vesicle. On the basis of our observations, we propose that formation of the coccolith utilizes the nuclear envelope–endoplasmic reticulum Ca²⁺‐store of the cell for the transport of Ca²⁺ ions from the external medium to the coccolith vesicle and that E. huxleyi calcite forms by ion‐by‐ion growth rather than by a nanoparticle accretion mechanism.     

The last 100,000 years in the western Mediterranean: sea surface water and frontal dynamics as revealed by coccolithophores

A quantitative analysis was carried out on coccolith assemblages from two Pleistocene cores (K1 and K10) from the western Mediterranean. The distribution of selected coccolithophore species provides new paleoclimatic and paleoceano-graphic data. A continuous sequence from the top of Isotope Stage 5 to the Holocene was recorded. The reversal in dominance between Gephyrocapsa muellerae and Emiliania huxleyi was dated in both cores at ca. 73 ka. At about 47 ka, E. huxleyi shows a regular increase, whereas G. muellerae progressively decreases in abundance. During interglacial periods, high concentrations of coccoliths are observed, whereas in glacial times, coccoliths are more diluted and the percentage of reworked forms increases as a consequence of the higher terrigenous input. After taking careful account of the dilution factor, we conclude that the production of coccolithophores was higher during warm periods. Maxima in coccolith concentrations coincide with highstand episodes, probably as a result of the intensification of the Atlantic flux into the Mediterranean across the Gibraltar Strait. This intensification could have produced an increase in nutrient content in the surface Mediterranean waters. During cold periods, the western Mediterranean front underwent a reduction in activity, probably due to an increase in the saline and/or thermal gradients between the superficial waters, and intermediate waters in the Liguro Provençal basin.     

Long-chain alkenes and alkenones in the marine coccolithophorid Emiliania huxleyi

Very long-chain n-alkenes and n-alkenones have been identified in the ubiquitous marine alga Emiliania huxleyi. The alkenes range from C₃₁ to C₃₈ and are almost exclusively odd-chain. Dienes, trienes and tetraenes were identified but no monoenes were found. The ketones ranged from C₃₇ to C₃₉ and consisted of both alken-2-ones and alken-3-ones, with trienes more abundant than dienes. Examination of three different forms of the alga, i.e. motile, sessile and coccolith, indicated that these ketones are formed throughout the growth cycle with only minor variations in the relative proportions of the individual compounds. Although these novel compounds have not been reported previously in organisms, they are widespread in marine sediments and may be useful biological markers for E. huxleyi input to sediments.