Diversity of the diatom genus Fragilariopsis in the Argentine Sea and Antarctic waters: morphology, distribution and abundance

Cefarelli, Adrián Oscar; Ferrario, Martha E.; Almandoz, Gastón O.; Atencio, A.; Akselman, Rut; Vernet, María

doi:10.1007/s00300-010-0794-z

Cited by 77 publications

(95 citation statements)

References 42 publications

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“…The gross morphology of the cell and the valve ultrastructure of the strains examined in light and electron microscopy fit the descriptions provided for F. kerguelensis by different authors (Hasle, 1965(Hasle, , 1968Hasle & Syvertsen, 1997;Cefarelli et al, 2010). The ultrastructure of the poroid hymen of our specimens corresponds perfectly with the TEM images provided by Hasle (1965), thus further confirming the uniformity of the species.…”

Section: Discussionsupporting

confidence: 88%

“…The pioneering work carried out by Hasle (1965Hasle ( , 1968 did not include information on the number and ultrastructure of the girdle bands. Recently, Cefarelli et al (2010) reported the presence of one valvocopula and one girdle band in F. kerguelensis. We here provide evidence for the presence of an additional thin band at the abvalvar end of the cingulum; this band bears a ligula that inserts between the open ends of the first cingular band.…”

Section: Discussionmentioning

confidence: 99%

“…Cells of Fragilariopsis kerguelensis can form long, ribbon-shaped chains, and they can be distinguished from other species in the genus by the strong silicification of their frustule and coarse pattern of the striae on the valve face (Hasle, 1965(Hasle, , 1968Hasle & Syvertsen, 1997;Cefarelli et al, 2010). Mechanical stress-testing of frustules of live cells of F. kerguelensis have demonstrated that the frustule architecture provides high mechanical resistance to deformation and breakage, which is probably an adaptation against grazing (Hamm et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

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Genetic characterization and life cycle of the diatomFragilariopsis kerguelensis

Fuchs

Scalco

Kooistra

et al. 2013

European Journal of Phycology

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The planktonic diatom Fragilariopsis kerguelensis plays an important role in the biogeochemical cycles of the Southern Ocean, where remains of its frustules form the largest deposit of biogenic silica anywhere in the world. We assessed the genetic identity of 26 strains, from cells collected at various sites in the Southern Ocean, using three molecular markers, LSU and ITS rDNA and rbcL. The LSU sequences were identical among the tested strains, ITS sequences were highly similar, and only one base pair difference was detected among the rbcL sequences. These results, together with a large number of successful mating experiments demonstrated that the strains belong to a single biological species. We investigated the mating system and life cycle traits of F. kerguelensis. Cell size diminished gradually in clonal strains. Gamete formation only occurred when strains of opposite mating type -within a cell size range of 7-36 µm -were mixed together. Two binucleate gametes were formed in each gametangium and gamete conjugation produced a zygote that had four nuclei and was surrounded by thin siliceous scales. Two out of the four nuclei subsequently degenerated and the zygote expanded to form an auxospore surrounded by a transverse and a longitudinal perizonium. Staining with the fluorochrome PDMPO provided for the first time a clear demonstration that the longitudinal perizonium is formed after auxospore expansion is complete. Initial cells produced within the mature auxospores were 78-101 µm in length. Various authors have shown that the average valve size of F. kerguelensis varies in sediment samples collected in regions and seasons with different primary production regimes and this parameter has thus been proposed as a biological proxy for palaeoproductivity. A better understanding of the life cycle of F. kerguelensis should help the design of future investigations aimed at testing the link between cell size distribution in the natural environment and the role that environmental factors might have in the regulation of population cell size.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Genetic characterization and life cycle of the diatomFragilariopsis kerguelensis

Fuchs

Scalco

Kooistra

et al. 2013

European Journal of Phycology

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“…The overall distribution of apical axis length is right-skewed (see Figure 7 top Ca. 5.4% of all valves (505 in total) are sized outside the dimensions reported in the literature [16][17][18], depicted by the dashed rectangle in Figure 8.…”

Section: Resultsmentioning

confidence: 99%

“…To test whether the species shows a different distribution of apical axis lengths between this and the other MISs, Kolmogorov-Smirnov tests were used (see Tables A2 and A3). MIS 1 represents the most recent material we analysed and thus the best to be compared to the investigations of [16][17][18]. Between this and MIS 5 the two-sided test did not support a significant difference.…”

Section: Resultsmentioning

confidence: 99%

Large-Scale Permanent Slide Imaging and Image Analysis for Diatom Morphometrics

et al. 2017

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Light microscopy analysis of diatom frustules is widely used in basic and applied research, notably taxonomy, morphometrics, water quality monitoring and paleo-environmental studies. Although there is a need for automation in these applications, various developments in image processing and analysis methodology supporting these tasks have not become widespread in diatom-based analyses. We have addressed this issue by combining our automated diatom image analysis software SHERPA with a commercial slide-scanning microscope. The resulting workflow enables mass-analyses of a broad range of morphometric features from individual frustules mounted on permanent slides. Extensive automation and internal quality control of the results helps to minimize user intervention, but care was taken to allow the user to stay in control of the most critical steps (exact segmentation of valve outlines and selection of objects of interest) using interactive functions for reviewing and revising results. In this contribution, we describe our workflow and give an overview of factors critical for success, ranging from preparation and mounting through slide scanning and autofocus finding to final morphometric data extraction. To demonstrate the usability of our methods we finally provide an example application by analysing Fragilariopsis kerguelensis valves originating from a sediment core, which substantially extends the size range reported in the literature.

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The 2008 Emiliania huxleyi bloom along the Patagonian Shelf: Ecology, biogeochemistry, and cellular calcification

Poulton

Painter

Young

et al. 2013

Global Biogeochemical Cycles

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[1] Coccolithophore blooms are significant contributors to the global production and export of calcium carbonate (calcite). The Patagonian Shelf is a site of intense annual coccolithophore blooms during austral summer. During December 2008, we made intensive measurements of the ecology, biogeochemistry, and physiology of a coccolithophore bloom. High numbers of Emiliania huxleyi cells and detached coccoliths (>1 × 10 3 mL À1and >10 × 10 3 mL À1 , respectively), high particulate inorganic carbon concentrations (>10 mmol C m À2 ), and high calcite production (up to 7.3 mmol C m À2 d À1 ) all characterized bloom waters. The bloom was dominated by the low-calcite-containing B/C morphotype of Emiliania huxleyi, although a small (<10 μm) Southern Ocean diatom of the genus Fragilariopsis was present in almost equal numbers (0.2-2 × 10 3 mL À1 ). Estimates of Fragilariopsis contributions to chlorophyll, phytoplankton carbon, and primary production were >30%, similar to estimates for E. huxleyi and indicative of a significant role for this diatom in bloom biogeochemistry. Cell-normalized calcification rates, when corrected for a high number of nonactive cells, were relatively high and when normalized to estimates of coccolith calcite indicate excessive coccolith production in the declining phase of the bloom. We find that low measures of calcite and calcite production relative to other blooms in the global ocean indicate that the dominance of the B/C morphotype may lead to overall lower calcite production. Globally, this suggests that morphotype composition influences regional bloom inventories of carbonate production and export and that climate-induced changes in morphotype biogeography could affect the carbon cycle.

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Diversity of the diatom genus Fragilariopsis in the Argentine Sea and Antarctic waters: morphology, distribution and abundance

Abstract: Fragilariopsis species composition and abun-

Cited by 77 publications

References 42 publications

Genetic characterization and life cycle of the diatomFragilariopsis kerguelensis

Genetic characterization and life cycle of the diatomFragilariopsis kerguelensis

Large-Scale Permanent Slide Imaging and Image Analysis for Diatom Morphometrics

The 2008 Emiliania huxleyi bloom along the Patagonian Shelf: Ecology, biogeochemistry, and cellular calcification

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