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(a-c) Combination cells of Syracosphaera mediterranea with marisrubri-type HOL coccoliths (GoA, 29 October 2017, 40 and 60 m). (d, e) HOL marisrubri-type coccospheres (GoA, 13 December 2018, 100 m, and 7 January 2021, 2 m). (f) Coccoliths with 5-10 perforations showing irregular walls and a domal shape. Coccoliths at apical pole (circum-flagellar coccoliths) have higher walls (GoA, 18 March 2018, 29 m). (g) Coccosphere and (h) coccoliths of C. leptoporus HOL with four to six perforations and a higher and evenly high tube wall (GoA, 17 August 2017, 40 m). (i) Polarized light microscopy image of S. mediterranea HOL marisrubri (GoA, 16 December 2020, 2 m). Scale bars: 5 µm, (f, h) 1 µm.
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Coccolithophores are a diverse group of calcifying phytoplankton, which are responsible for a large part of the modern oceanic carbonate production. Here, we describe novel or poorly known coccolithophores and novel life cycle combination coccospheres detected in samples collected either in the Gulf of Aqaba in the northern Red Sea or in the Gulf o...
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... sp. A Winter et al. 1979 pl. IV fig. 9 ?Syracosphaera histrica Agbali 2014 pl. 7 fig. 7 (the question mark was used by Agbali, 2014, who tentatively identified this specimen of S. winteri as S. histrica) Syracosphaera sp. Jordan 1988 pl. 9a-b, pl. 10 a Syracosphaera sp. imaged on the EMIDAS website (http:// www.emidas.org, last access: 22 July 2021) -seven images showing three collapsed ...
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... mediterranea Lohmann 1902 HOL marisrubri type Fig. 7 The heterococcolithophore S. mediterranea (Coronosphaera mediterranea) is commonly found in temperate to tropical waters. Three distinct alternate life cycle stages bearing holococcoliths have been recognized; S. mediterranea HOL wettsteinii type, S. mediterranea HOL gracillima type and S. mediterranea HOL hellenica type. These were ...
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... samples from the GoA, we observed three unambiguous combination coccospheres of S. mediterranea heterococcoliths with holococcoliths of a fourth type that is very different to the wettsteinii, gracillima and hellenica types (Fig. 7a-c). Complete coccospheres of the fourth holococcolith-bearing type were also detected (Fig. 7d, e). The coccospheres are spheres of 13 to 18 µm length. The holococcoliths of this variant are about 2 to 2.6 µm long, consisting of an open tube with an indented wall open distally and subdivided by vertical septae. These septae define 6 to 10 ...
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... samples from the GoA, we observed three unambiguous combination coccospheres of S. mediterranea heterococcoliths with holococcoliths of a fourth type that is very different to the wettsteinii, gracillima and hellenica types (Fig. 7a-c). Complete coccospheres of the fourth holococcolith-bearing type were also detected (Fig. 7d, e). The coccospheres are spheres of 13 to 18 µm length. The holococcoliths of this variant are about 2 to 2.6 µm long, consisting of an open tube with an indented wall open distally and subdivided by vertical septae. These septae define 6 to 10 pores, frequently including one or two central pores. The septae are higher in the center of ...
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... by vertical septae. These septae define 6 to 10 pores, frequently including one or two central pores. The septae are higher in the center of the coccolith, giving the distal surface a domal shape, but there is no central boss. Possible CFCs were detected in a single complete coccosphere, with a more elevated central area than the other coccoliths (Fig. 7e, f). We informally refer to the newly described variant as S. mediterranea HOL marisrubri (mare: sea, rubrum: red) type in reference to the Red Sea where samples were collected. In addition to the specimens from this study we have found two other examples from the Gulf of Mexico: one illustrated by Agbali (2014, pl. 5, fig. 14) labeled as ...
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... down to the proximal surface. The tube wall shows hexagonal fabric, and the crystallites have radial c axes (birefringent in plan view in light microscopy). The fabric of the septae is not obviously different, but they are nonbirefringent in plan view in LM (Fig. 7i), so the calcite crystallites must have vertical c ...
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... to this group and could easily be confused with either Calcidiscus leptoporus subsp. quadriperforatus HOL or Scyphosphaera apsteinii HOL. Holococcoliths of the marisrubri type can be separated from those of Calcidiscus quadriperforatus HOL by having more perforations (5-10 vs. 4-6), a more domal distal surface, and a lower and irregular wall (Fig. 7g). They can be separated from those of Scyphosphaera apsteinii HOL by being smaller (2-3 µm vs. 3-4 µm) with fewer pores (5-10 vs. 8-20), having a more domal distal surface and lacking a central ...
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... The circum-flagellar coccoliths are located near the flagellar opening and are perpendicular to the position of the appendage coccoliths surrounding the antapical pole across the coccosphere (Gaarder, 1967;Manton et al., 1977;Young et al., 2009). In addition, the appendage coccoliths in Ophiaster are formed of strings of coccoliths, termed osteoliths, and they demonstrate a rather rectangular shape (Keuter et al., 2021;Manton et al., 1977;Young et al., 2009) as opposed to a thin appendage with a fine tip. Second, the species P. scenozonion, which is the type species of the genus Pseudowigwamma Thomsen, is characterised by coccospheres that are monothecate and monomorphic consisting of body coccoliths that are simple rings. ...
Based on scanning electron microscopy observations, a new species of the coccolithophore genus Calciopappus (Syracosphaeraceae, Prymnesiophyceae) is described from the surface waters off Bergen and from the lower photic zone of sub-tropical and tropical waters. Morphological, coccolith rim structure and biometric analyses strongly support separation of this morphotype from the two described Calciopappus species, but inclusion of it within the genus. The new form differs from the other species in being noticeably smaller and in morpho-structural details of each of the three coccolith types that form the coccosphere: (1) the body coccoliths have an open central area; (2) the whorl coccoliths have a wide central opening and two thumb-like protrusions; and (3) the appendage coccoliths are curved. On this basis, the species is formally described as Calciopappus curvus sp. nov., its systematic affinity is discussed and compared with other extant coccolithophores.
Diatoms dominate primary production in nutrient-rich ecosystems. Less is known about the diversity and ecology of diatoms in low latitude, oligotrophic ecosystems. Here, we examined using scanning electron microscopy the seasonal succession of planktonic diatoms in the Gulf of Aqaba (Red Sea), a subtropical ecosystem that alternates between stratified, oligotrophic conditions during spring/summer resembling open-ocean oligotrophic regions and deeply mixed, mesotrophic conditions during fall/winter. Diatom diversity and density were both lower during the stratified season. Pennate species comprised >90% of the diatom counts. A shift in diatom density involving an increase in centric diatom dominance was detected at mid-winter, as temperature declined and nitrogen concentrations exceeded ∼0.5 µmol L ⁻¹ . This occurred markedly later relative to total phytoplankton, suggesting higher nutrient requirements for diatom growth. Faster community succession was detected during winter. Peak diatom densities occurred during the mixing-to-stratification transition at the peak of nutrient concentrations, coinciding with the annual peak in chlorophyll a (bloom). Blooms were numerically dominated by small cells, but significant proportions of chain-forming centrics ( Chaetoceros and Leptocylindrus ) and spores were also detected specially during colder years as mixing was deeper and nutrient higher. Blooms last about 1-month and declined rapidly to low cell densities, along with water column restratification and nutrient depletion, involving the replacement of centric species by pennates. Overall, marked seasonal dynamics and contrasts were detected, along with distinct variations in the prevalence of pennate, centric and large chain-forming species, highlighting underlying eco-physiological differentiation and the importance of each morpho-group in oligotrophic regimes.
The genera Ericiolus and Mercedesia are distinctive extant coccolithophores that are characterized by monothecate, monomorphic coccospheres with one type of triradiate star-shaped nannoliths. The two genera were described from the Danish coastal waters, the surface waters of the Arctic, and the Southern Oceans. During a study of samples from the low photic zone of the Mediterranean and Sargasso Seas, and from the subtropical gyres of the South-eastern Pacific and the South Atlantic Oceans, 44 collapsed coccospheres with triradiate star-like nannoliths were observed via scanning electron microscopy. Observations on the morphologies and biometric assessments of these specimens revealed that three distinct sets of nannoliths can be distinguished and that these were morphologically differentiated from all currently known species of Ericiolus and Mercedesia. The new forms and the previously described species of Ericiolus and Mercedesia were, however, similar, as they all demonstrated a distinctive set of collectively shared morphological characters and almost identical size ranges. On the basis of this, and instead of describing a third genus for the same group of nannoliths, we preferred to taxonomically synonymize Mercedesia with Ericiolus and revise the definition of Ericiolus. Therefore, we describe three new species, Ericiolus bendifii sp. nov., Ericiolus sheldoniae sp. nov. and Ericiolus mattioliae sp. nov., and an incompletely defined taxon, as Ericiolus cf. bendifii, and establish the new combinations E. aspiphorus comb. nov., E. multistellatus comb. nov. and E. pusillus comb. nov.
A two-year (2017, 2018) study of coccolithophores was undertaken in the Gulf of Aqaba in the northern Red Sea to 1) determine the local diversity and community succession patterns with high temporal and taxonomic resolution, 2) determine the contribution to exported inorganic carbon and 3) evaluate changes in communities relative to those in the mid-1970's reported in Winter et al. (1979). As typical, the oceanographic conditions in the Gulf alternated between stratified, oligotrophic through spring/summer, and mesotrophic during winter due to deep convective mixing. Noticeably, the second summer (2018) was warmer resulting in a more pronounced thermocline. Overall, the coccolithophore dynamics followed the seasonal changes in oceanographic conditions. During the mixing period, coccolithophores were denser (>25 coccospheres mL⁻¹) and were estimated to account on average for 3.46% of the total Chl-a. The communities were fairly homogeneous through depths and over time with a marked dominance of Emiliania huxleyi and Gephyrocapsa ericsonii. During the stratified season, coccolithophore densities were lower, particularly at the surface, such that coccolithophores were estimated to represent on average 0.72% of the total Chl-a. However, the diversity was higher and a clear vertical zonation developed with well-defined upper, intermediate and deep-dwelling communities. These included Umbellosphaera spp., Rhabdosphaera clavigera, a variety of Syracosphaera spp., holococcolithophores and Florisphaera profunda, respectively, as typical in oligotrophic systems. This further underscores the pelagic nature of the Gulf of Aqaba. Noticeably, however, coccolithophores declined in abundances and diversity during 2018, possibly due to the warmer conditions. The relative export of inorganic carbon by coccolithophores largely correlated with the density of living communities, representing <4% and <10% of total inorganic carbon exports during the stratified and mixing periods, respectively. A marked differentiation between different coccolithophore life phases was also detected. Broadly, holococcolithophores inhabited preferentially shallow, oligotrophic water layers in the stratified season, while heterococcolithophores prevailed in deeper water layers or in winter. Yet, species-specific deviations to this pattern were also detected. Finally, comparisons with the 1970's revealed marked changes compared to current communities. G. ericsonii appeared less prevalent and Umbellosphaera spp. displayed a wider temporal residence through spring/summer. Moreover, F. profunda and other deep dwelling species absent in the past are now common during the peak of summer. These observations are indicative of changes in local microbial communities, possibly linked to the ongoing rise in sea temperatures. This study provides a detailed baseline information on coccolithophores for future reassessments of community changes in the GoA.
