Huxleyi Type Research Articles

Coccolithophore response to changes in surface water conditions south of Iceland (ODP Site 984) between 130 and 56 ka

Quantitative coccolithophore analyses were performed using sediments from Ocean Drilling Program (ODP) Site 984, located south of Iceland close to the modern location of the Polar Front, to reconstruct climatically induced variations in surface water conditions from 130 to 56 ka, spanning the end of Marine Isotope Stage (MIS) 6 to the beginning of MIS 3. For this purpose, changes in the coccolith assemblages (e.g., abundances, accumulation rates, composition, diversity and preservation, as well as coccolith carbonate) and variations in sizes and morphotypes of Gephyrocapsa muellerae and Emiliania huxleyi were investigated.The coccolith assemblages were generally of low diversity and were mostly dominated by G. muellerae throughout most of the record. Two intervals of relatively warm surface water expansion (MIS 5e, 5a) were identified by increased coccolith numbers, coccolith accumulation rates (CAR), and highest coccolith carbonate content, and interpreted to be associated with the expansion of the relatively warm Irminger Current (IC). The low coccolith numbers and low CAR during the interval MIS 5d to 5b point to much lower sea-surface temperatures and the decreased influence of the warm IC. Furthermore, MIS 5c is notable due to the absence of E. huxleyi accompanied by lowest species diversity, which suggest either cooler or less productive surface water conditions during this time interval.Another intriguing result of this research is the observed significant increase in the mean length of the G. muellerae distal shield (> 15%) from the beginning of MIS 5e to MIS 4. Furthermore, E. huxleyi occurs almost exclusively as Type B/C throughout MIS 5 and is particularly characterized by a considerable proportion of strongly calcified types during MIS 5a. Emiliania huxleyi Type A is first determined in MIS 5a and became the dominant morphotype during MIS 4. In addition, E. huxleyi (> 4 μm) commonly occurred during MIS 5e and 5a, during intervals of warmer surface waters. It seems likely, that E. huxleyi as well as G. muellerae went through various adaptations during MIS 5, which may have led to a global step in the exchange in dominance between the two species at the end of MIS 5, recorded in most ocean basins.

Seasonal living coccolithophore distribution in the enclosed coastal environments of the Thessaloniki Bay (Thermaikos Gulf, NW Aegean Sea)

Living coccolithophores collected from a yearly time interval, January to December 2016, at the SP1 station of the Thessaloniki Bay, an enclosed coastal environment located in the inner part of the Thermaikos Gulf (Northwestern Aegean Sea) were analyzed to determine their seasonal variation and evaluate the effects of environmental factors on their density, species composition and distribution. Our results showed that coccolithophores constituted a significant component of the phytoplankton community and were characterized by the dominance of few opportunistic species, as an impact of eutrophic environmental conditions. Temperature seasonal cycle and the variations in nutrient inputs from riverine and/or anthropogenic sources seem to control the seasonal pattern of coccolithophores. Emiliania huxleyi with densities as high as ∼4.0 × 105 cells l−1 predominated during the late spring–early summer, whereas a strong dominance of Gephyrocapsa oceanica with densities ∼2.0 × 105 cells l−1 was observed during the late summer and the autumn. Emiliania huxleyi appeared to dominate the coccolithophore assemblages once more during the winter; while Helicosphaera carteri was continuously present during the wintertime (exceeding ∼2.7 × 103 cells l−1). Emiliania huxleyi was entirely represented by morphotype type A in the studied samples. Morphometric analysis of E. huxleyi coccoliths indicated that the population is dominated by lightly calcified forms, although an increase of more heavily calcified coccoliths was observed during late autumn-early spring in line with the well-documented seasonal succession pattern of E. huxleyi type A forms in the Aegean Sea.

Vertical fluxes of coccolithophores and foraminifera and their contributions to CaCO3 flux off the coast of Ensenada, Mexico

Coccoliths and foraminifera fluxes and their contributions to CaCO3 were estimated by analyzing the material collected by a sediment trap installed in the area adjacent to Ensenada, Baja California (Mexico). Coccoliths were identified and counted from images obtained with a Zeiss-Supra 55VP scanning electron microscope. Foraminifera were identified and analyzed with a Leica EZ4 stereoscope. Total CaCO3 was determined by coulometry. A total of 33 species of coccoliths were recorded; the most abundant species were Emiliania huxleyi type A, Gephyrocapsa oceanica (Equatorial), E. huxleyi type B, and G. oceanica (Larger), contributing 74% of total coccolith flux. The maximum flux of coccoliths was 1,539 × 106 m–2·d–1 in sample A-8, the minimum zero in sample A-10, and the average 1,028 × 106 m–2·d–1. Coccolith contribution to CaCO3 content ranged from 0.14 mg·m–2·d–1 in sample A-12 to 25.00 mg·m–2·d–1 in sample A-1, with an average of 5.60 mg·m–2·d–1. Helicosphaera carteri made the highest contribution with 10.00 mg·m–2·d–1 in sample A-1, and the rest of the species contributed <7.00 mg·m–2·d–1. Six genera of planktonic foraminifera were identified: Globigerina, Neogloboquadrina, Globorotalia, Pulleniatina, Globigerinoides, and Orbulina. The maximum flux of foraminifera was recorded in summer (513 m–2·d–1) and the minimum in spring (9 m–2·d–1). Benthic foraminifera were found to make an important contribution, even greater than the contribution from planktonic foraminifera, reflecting horizontal resuspension and/or transport processes. CaCO3 contributions by coccoliths and foraminifera were <1% of total CaCO3, and the rest was contributed by fragments of the other calcareous groups.

Biogeographic distribution of living coccolithophores in the Pacific sector of the Southern Ocean

Abstract This paper adds to a series of studies addressing the distribution of living coccolithophores in the Southern Ocean (SO). We investigated plankton samples collected during RV Polarstern cruise ANT-XXVI/2 (from 27th November 2009 to 27th January 2010) along a broad E–W transect in the Pacific sector of the SO during austral summer. One hundred and fifty samples from twenty-nine stations were collected from the upper 150 m of the water column. Both coccoliths and coccospheres per sample were counted separately using a scanning electron microscope (SEM). The highest abundances of 640 · 103 coccospheres/l were reached close to the Subtropical Front (STF) and increases in the numbers of coccospheres and coccoliths were found both at the Subantarctic Front (SAF) and the Polar Front (PF). However, the numbers decrease southward until almost a monospecific assemblage and sporadic record of Emiliania huxleyi (types B/C and C) south of the PF. Thirty-three coccolithophore species, including sixteen species found as isolated coccoliths, were identified of which E. huxleyi is clearly the most dominant coccolithophore taxon in the studied samples. Two main coccolithophore assemblages were established coincident with areas bounded by the oceanographic fronts: the Polar Front Zone (PFZ) and Subantarctic Zone (SAZ). In the upper photic zone of the SAZ, Acanthoica quattrospina, Calcidiscus leptoporus, Coccolithus pelagicus (sensu lato) HOL, E. huxleyi type A, Ophiaster spp. and Syracosphaera spp. among others were found. The PFZ was characterized by a reduced number of species, i.e., Calciopappus caudatus, E. huxleyi types B, B/C and C, as well as Pappomonas spp. and Papposphaera spp. The sea surface temperature measured in situ was the most prominent factor influencing coccolithophore diversity, distribution and assemblage compositions in the Pacific sector of the SO during austral summer. Coccolithophore biogeography in the study area showed marked differences with the northern high latitudes; the reduced presence of the cold water species Coccolithus pelagicus, abundant in the (sub) Arctic region, and the dominance of E. huxleyi type B/C and C in the SO contrasts with the dominance of E. huxleyi types A and B in the North Atlantic. Findings such as these cover existing gaps in an unexplored area of the SO as well as supporting previous research performed in neighboring areas. The current coccolithophore numbers and assemblage distribution in relation to the frontal dynamics of the SO provide valuable information for potential future paleoceanographic reconstructions.

Vertical and lateral variations in coccolithophore community structure across the subtropical frontal zone in the South Atlantic Ocean

In this study the coccolithophore compositions of 11 plankton depth stations along a N–S transect from the South Atlantic Subtropical Gyre to the Subantarctic Zone were examined qualitatively and quantitatively. The lateral and vertical distribution patterns of not only the most abundant taxa but also of the morphotypes of distinct species complexes, such as Calcidiscus leptoporus, Emiliania huxleyi, and Umbellosphaera tenuis were the focus. Geographic variation among morphotypes mirrors different ecological affinities of the members of a species complex. Multivariate statistics were used to infer the relationship between a set of known environmental data and species concentrations. The results of the detrended Canonical Correspondence Analysis (CCA) revealed the presence of distinct species assemblages. The Subtropical Gyre assemblage within the upper 50 m of the photic zone is mainly composed of Umbellosphaera irregularis, U. tenuis types III and IV, Discosphaera tubifera, Rhabdosphaera clavigera, S. pulchra and E. huxleyi var. corona, adapted to warm and oligotrophic conditions. In the deeper photic zone abundant Florisphaera profunda, Gephyrocapsa ericsonii and Oolithotus spp. are encountered, benefiting from higher nutrient concentrations in the vicinity of the nutricline. A well-defined Subtropical Frontal Zone (STFZ) association is clearly dominated by E. huxleyi types A and C throughout the upper 100 m of the water column. Secondary contributors in the upper photic zone are Syracosphaera spp. (mainly S. histrica, S. molischii), Michaelsarsia elegans, Ophiaster spp. and U. tenuis type II. This assemblage is associated with cooler, nutrient-rich waters. E. huxleyi type B is found deeper in the water column. Here it is accompanied by Algirosphaera robusta, G. muellerae, and S. anthos indicating a tolerance of lower light availability in environments with elevated productivity. C. leptoporus spp. leptoporus shows relatively high cell numbers in all sampled water levels throughout the STFZ. Interestingly, its coccoliths are often smaller 5 μm in lith diameter. The mean coccolithophore assemblages of a station were compared to the underlying surface sediment assemblages. For the most part, the distribution of the morphotypes is reflected in the sedimentary archive, thus proving their potential as paleoecological proxies.

Coccolithophore assemblages and morphotypes of Emiliania huxleyi in the boundary zone between the cold Oyashio and warm Kuroshio currents off the coast of Japan

Living coccolithophore assemblages were studied off the Japanese coast in the boundary zone between the cold Oyashio and the warm Kuroshio Currents as well as in adjacent water masses. A total of 64 coccolithophore taxa were identified. Ten taxa that comprised more than 10% of at least one sample were designated major taxa. Morphological observations and morphometric measurements enabled us to sub-divide the Emiliania huxleyi into four morphotypes: Type A, Type B, Type B/C, and Type B/C-2. Based on the composition of major taxa and morphotypes of Emiliania huxleyi, four coccolithophore assemblages were recognized, corresponding to distinct water masses: Oyashio Current, Tsugaru Warm Current, Kuroshio Current, and Western North Pacific Central Water (WNPCW). In the Oyashio Current regime, the standing crop of coccolithophores was high, although diversity was low. The floral assemblage was dominated by E. huxleyi Type B and consistently contained Coccolithus pelagicus ssp. pelagicus HOL, Calciopappus caudatus, and Syracosphaera orbiculus. In the Tsugaru Warm Current regime, the flora was characterized by abundant E. huxleyi Type B/C-2 and Gephyrocapsa oceanica as well as by relatively common Braarudosphaera bigelowii. In the Kuroshio Current regime, E. huxleyi Type A, Gephyrocapsa ericsonii, or G. oceanica were abundant. The coccolithophore flora in the WNPCW was characterized by abundant E. huxleyi Type A, Discosphaera tubifera, and Umbellosphaera tenuis Type IV. Large Emiliania huxleyi specimens (≥4.2 μm in length) only occurred north of the Oyashio Front, while to the south, E. huxleyi were consistently ≤4.1 μm long, regardless of the morphotype. Large E. huxleyi can be a useful paleoenvironmental indicator for reconstructing past migrations of the Kuroshio and Oyashio Currents in the North Pacific Ocean.

Spatial dynamics of coccolithophore assemblages in the Equatorial Western-Central Pacific Ocean

The spatial distribution of living coccolithophores was studied in the Western-Central Equatorial Pacific Ocean during November–December, 1990 and September–October, 1992. The highest local concentration of coccolithophores occurred at the thermocline in well-stratified waters, but at sea-surface level in dynamic waters. In total, 111 coccolithophore taxa were recognized, some of which exhibited hydrographically controlled variation in their absolute abundance. Gephyrocapsa oceanica and Oolithotus antillarum were abundant in the upwelling front. Most of the lower photic dwellers were abundant in the tropical to subtropical stations regardless of the water stratification. The coccolithophore flora of well-stratified waters could be distinguished from the upwelling front flora by the higher abundance of Umbellosphaera irregularis and lower abundance of G. oceanica. The temperature mixed-water flora was characterized by a high abundance of Emiliania huxleyi. The vertical distribution of all coccolithophore taxa, except three placolith-bearing species, Gephyrocapsa ericsonii, G. oceanica and E. huxleyi, was controlled by upper photic-zone temperature and water stratification. The upper or lower vertical distribution limits of many coccolithophore taxa coincided with the top of the thermocline. The most common 27 taxa were grouped into four ecological groups, Upper Photic-zone Group (UPG), Middle Photic-zone Group (MPG), Lower Photic-zone Group (LPG) and Omnipresent Group (OPG), on the basis of their vertical distribution. By analyzing the hydrographic control on the vertical distribution of these four ecological groups, four ecological assemblages were recognized: High Temperature; Warm Oligotrophic; Warm Eutrophic; and Temperate Mixed-water Assemblages. In equatorial waters, the total coccolithophore assemblage across the photic-zone was controlled by the population in the upper photic-zone. The UPG monopolized the upper photic-zone flora in the High Temperature Assemblage. In the Warn Oligotrophic-water Assemblage, common OPG accompanied abundant UPG in the upper photic-zone. The upper photic-zone of the Warm Eutrophic Assemblage consisted of UPG, MPG and OPG.Emiliania huxleyi and Gephyrocapsa oceanica, the major component of OPG, displayed intra-specific morphological variations. G. oceanica Type 1 was restricted to the upper photic-zone of well-stratified oligotrophic waters. Conversely, in these waters E. huxleyi Type C and G. oceanica Type 2 only occurred below the thermocline. These two taxa also coexist with G. oceanica Type 3 and E. huxleyi Type A in the upper photic zone of dynamic waters.

Distribution of calcareous nannoplankton near the Subtropical Convergence, south of Tasmania, Australia

The floral composition of living calcareous nannoplankton collected from surface waters near the Subtropical Convergence (STC), offshore south-eastern Tasmania, in January 1994 is presented. Emiliania huxleyi represented more than 90% of all coccolithophorids. Scanning electron microscopy showed a substantial increase in intraspecific variation of E. huxleyi, and in variation in coccolith size of Calcidiscus leptoporus, E. huxleyi type A and C. leptoporus (small), north of the STC. It is postulated that the percentage abundance of these taxa may be used to determine the position andlor shift of the STC zone through time, and therefore may be of use for palaeoceanographic studies.

Growth of harmful marine algae in multispecies cultures

Mixtures of harmful and harmless algae were grown in discontinuously diluted batch cultures under ammonium, nitrate and phosphate limitation, and at different irradiances (20-500 jjjnol quanta m s~'). The species used were Chrysochromulina polylepis, Emiliania huxleyi type B, Rhodomonas sp., the dinoflagellales Fibrocapsa japonica, Gymnodinium simplex, Gyrodinium aureolum, Heterocapsa triquetra, Heterosigma carterae, Prorocentrum micans and Alexandrium tamarense, the diatoms Chaetoceros socialis, Cymatosira belgica, Ditylum brightwellii, Laudcria borealis, Odontelta aunla, Pseudonitzschia pungens, Streptotheca tamesis, and the cyanobacterium Synechococcus. Their growth response in the mixed algal cultures is discussed in relation to their abundance in different natural habitats. In comparison with the other non-diatoms, the mixotrophic Cpolylepis grew fast under all tested nutrient and light limitations. Emiliania huxleyi grew well under nitrogen (N) limitation (with nitrate as N source) and at irradiance levels from 15 up to 500 u.mol quanta m~ s. No growth of calcifying cells could be detected under N limitation when ammonium was used as N source. Rhodomonas grew reasonably well under ammonium-N limitation and grew fast at the highest irradiance. The dinoflagellates were poor competitors compared to the Prymnesiophyceae. The environmental fitness of the Prymnesiophyceae appears to be closely related to the reproductive capacity of the vegetative stage, whereas the natural distribution of dinoflagellates seems more closely dependent on the generative reproduction-related specific life cycle characteristics of the individual species. The marine diatoms include a mixture of both types of species. Some marine diatom species clearly have the capability to outcompete non-diatoms under different types of nutrient and light limitations when silicate is in excess. Other diatoms seem to be poor competitors.

Seasonal changes in coccolithophore densities in the Southern California Bight during 1991–1992

Seasonal changes in coccolithophore cell densities in the San Pedro Basin, Southern California Bight, were investigated for the period October 1991 to September 1992. Coccolitho phore cell densities ranged from 6.3 × 10 4 coccospheres per liter in March 1992 to 0 cells per liter in November 1991. High coccolithophore concentrations occurred in late winter and spring, and low densities occurred in the summer and fall. The high coccolithophore densities during spring 1992 were associated with unusually low surface nutrient concentrations and a lack of upwelling, suggesting that the high densities were not part of a typical spring phytoplankton bloom in this region. We propose that the suppression of upwelling during spring 1992 may have been related to the prevailing ENSO conditions. Emiliania huxleyi type A dominated the total coccolithophore population throughout the year, Umbilicosphaera sibogae var. sibogae being the second most important contributor to the coccolithophore assemblages.

Standing stocks of PIC, POC, PON andEmiliania huxleyicoccospheres and liths in sea water enclosures with different phosphate loadings

Abstract Time series of the standing stocks of particulate inorganic carbon (PIC), particulate organic carbon (POC) and organic nitrogen (PON), and the numbers and type of Emiliania huxleyi coccospheres and detached coccoliths were determined in sea water enclosures with low, intermediate and high phosphate loadings. In the enclosures with the low and the intermediate phosphate loadings, intense blooms of E. huxleyi type A developed. PIC increased exponentially (µ = 0.3 day−1) and reached maxima of 0.3 g C m−3. PIC increased both during night and day. At the peak of the blooms, E. huxleyi made up 80 and 50 % of total POC in the enclosure with the low and the intermediate phosphate loading, respectively. High phosphate loading favoured other phytoplankton species and had negative effects on the abundance of E. huxleyi pO % of total POC) and the PIC standing stock (µ = 0.2 day−1; maximum 0.09 g C m−3). PIC per E. huxleyi cell differed between the enclosures and increased with decreasing net specific growth ...

CELL AND GROWTH CHARACTERISTICS OF TYPES A AND B OF EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE) AS DETERMINED BY FLOW CYTOMETRY AND CHEMICAL ANALYSES1

ABSTRACTTwo 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.

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

ABSTRACTCulture 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.