| 1. |
- Taylor, Rebecca L, et al.
(författare)
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SEASONAL VARIABILITY IN POLYUNSATURATED ALDEHYDE PRODUCTION POTENTIAL AMONG STRAINS OF SKELETONEMA MARINOI (BACILLARIOPHYCEAE)
- 2009
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 45:1, s. 46-53
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Tidskriftsartikel (refereegranskat)abstract
- The cosmopolitan bloom-forming diatom Skeletonema marinoi Sarno et Zingone is known to produce toxic polyunsaturated aldehydes (PUAs) in response to cell damage that can affect a diverse suite of organisms, including grazing species and competitor plankton species. The production of PUAs in nine different S. marinoi strains isolated at three different times of the year (spring, summer, and autumn) was assessed in relation to the predominant conditions at the time of isolation from Gullmar Fjord, Skagerrak. During the initial stages of growth, PUA production potential of S. marinoi was generally the highest in summer strains, although there was a substantial variation among strains isolated at the same time. Spring strains, however, showed a strong capacity for increased PUA production potential in later stage cultures with diminishing nutrient levels, reaching amounts similar to those observed in summer strains. In contrast, PUA production potentials of summer and autumn strains did not change significantly from the original values. There is negligible grazing pressure during the spring bloom in Gullmar Fjord, but a potential for high competition for resources, such as nutrients, toward the later stages of the bloom. In contrast, grazing pressure is much greater during summer and autumn, and there may also be nutrient limitation at this time. The PUA production potentials of S. marinoi appear to reflect the ecological conditions at the time of isolation with higher production potentials in strains isolated when conditions were likely to be less beneficial for survival.
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| 2. |
- Figueroa, R I, et al.
(författare)
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Effects of parental factors and meiosis on sexual offspring of Gymnodinium nolleri (Dinophyceae).
- 2006
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 42:2, s. 350-362
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Tidskriftsartikel (refereegranskat)abstract
- Clonal strains of the dinoflagellate Gymnodinium nolleri Ellegaard and Moestrup were intercrossed to determine if cyst-related traits are genetically regulated and to clarify unknown aspects in the sexuality of this species. The objectives were to determine whether the parental identity influenced the physiological and morphological aspects of the cyst offspring, and to describe and compare nuclear development and cell division of encysting and non-encysting zygotes. Variables characteristic of each parental cross (difference in growth rates among parents, cyst production (CP), and genetic distance (GD) among parents assessed via an amplified fragment length analysis analysis) were studied to seek for possible relationships of the parental crosses with some characteristics of the cyst offspring (cyst size, length of dormancy period, germination success, and germling viability (V)). A principal component analysis using these variables showed three main results: (1) the dormancy period of cysts responded to a simple pattern of inheritance, (2) the larger the GD between parents, the smaller the CP, and progeny V, and (3) the size of cysts was influenced by both CP and the parental strain identity. A stable inheritance of the short dormancy period (14.6±5.5 days), dominant over medium (31.0±8.5 days) and long periods (52.7±9.2 days), was confirmed through two subsequent generations of cysts. The regulation of the sexual processes by a multiple loci system is discussed based on the pattern of inheritance of the dormancy period and the number of sexual recombination events recorded within cultures with self-CP capability. Fusion of the gamete nuclei happened 0–48 h after the total cytoplasmic fusion. The nucleus of the zygote was bilobed and had thick and distinct chromosomes. Similar processes of nuclear and cell division occurred in the non-encysting or encysting planozygote, and were characterized by the loss of the chromosomal structure, an apparent increase of the DNA content, and the formation of thinner chromosomes.
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| 3. |
- Figueroa, Rosa, et al.
(författare)
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Life cyle and sexuality of the freshwater raphidophyte Gonyostomum semen (Raphidophyceae)
- 2006
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 42:4, s. 859-871
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Tidskriftsartikel (refereegranskat)abstract
- Previously unknown aspects in the life cycle of the freshwater flagellate Gonyostomum semen (Ehrenb.) (Raphidophyceae) are described here. This species forms intense blooms in many northern temperate lakes, and has increased in abundance and frequency in northern Europe during the past decades. The proposed life cycle is based on observations of life cycle stages and transitions in cultures. Viable stages of the life cycle were individually isolated and monitored by time-lapse photography. The most common processes undertaken by the isolated cells were: division, fusion followed by division, asexual cyst formation, and sexual cyst formation. Motile cells divided by two different processes. One lasted between 6 and 24 h and formed two cells with vegetative cell size and with or without the same shape. The second division process lasted between 10 and 20 min and formed two identical cells, half the size of the mother cell. Planozygotes formed by the fusion of hologametes subsequently underwent division into two cells. Asexual cyst-like stages were spherical, devoid of a thick wall and red spot, and germinated in 24-48 h. Heterogamete pairs were isogamous, and formed an angle of 0-90 degrees between each other. Planozygote and sexual cyst formation were identified within strains established from one vegetative cell. The identity of these strains, which was studied by an amplified fragment length polymorphism analysis, was correlated with the viability of the planozygote. Resting cyst germination was described using cysts collected in the field. The size and morphology of these cysts were comparable with those formed sexually in culture. The excystment rate was higher at 24 degrees C than at 19 or 16 degrees C, although the cell liberated during germination (germling) was only viable at 16 degrees C. The placement of G. semen within the Raphidophyceae family was confirmed by sequence analysis of a segment of the 18S ribosomal DNA.
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| 4. |
- Hagen, Christoph, et al.
(författare)
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Functional aspects of secondary carotenoids in haematococcus lacustris (volvocales). III. Action as a "sunshade"
- 1994
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 30:2, s. 241-248
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the protection from photoinhibition by different developmental stages of Haematococcus lacustris [Girod] Rostafinski using chlorophyll fluorescence measurements of single cells and suspensions. An overall correlation between higher cellular content of secondary carotenoids and the capacity to withstand excessive irradiation was observed in flagellated cells and aplanospores of H. lacustris. Low-light-reversible spreading of extra-chloroplastic secondary carotenoids occurred in the periphery of the cell during strong irradiation. This process resulted in increased shading of the cup-shaped chloroplast as demonstrated by a decrease in chlorophyll fluorescence. Extrachloroplastic accumulation of secondary carotenoids in H. lacustris can be interpreted as a specific adaptation to habitats that exhibit strong insolation.
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| 5. |
- Rengefors, Karin, et al.
(författare)
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Marine-derived dinoflagellates in Antarctic saline lakes: annual dynamics and community composition
- 2008
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 44:3, s. 592-604
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Tidskriftsartikel (refereegranskat)abstract
- The saline lakes of the Vestfold Hills in Antarctica offer a remarkable natural laboratory where the adaptation of planktonic protists to a range of evolving physiochemical conditions can be investigated. This study illustrates how an ancestral marine community has undergone radical simplification leaving a small number of well-adapted species. Our objective was to investigate the species composition and annual dynamics of dinoflagellate communities in three saline Antarctic lakes. We observed that dinoflagellates occur year-round despite extremely low PAR during the southern winter, which suggests significant mixotrophic or heterotrophic activity. Only a small number of dominant dinoflagellate species were found in each lake, in contrast to the species-rich Southern Ocean from which the lake communities are believed to be derived. We verified that the lake species were representatives of the marine polar dinoflagellate community, and not freshwater species. Polarella glacialis Montresor, Procaccini et Stoecker, a bipolar marine species, was for the first time described in a lake habitat and was an important phototrophic component in the higher salinity lakes. In the brackish lakes, we found a new sibling species to the brackish-water species Scrippsiella hangoei (J. Schiller) J. Larsen, previously observed only in the Baltic Sea.
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| 6. |
- Teneva, Ivanka, et al.
(författare)
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Molecular and phylogenetic characterization of Phormidium species (Cyanoprokaryota) using the cpcB-IGS-cpcA locus
- 2005
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 41:1, s. 188-194
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Tidskriftsartikel (refereegranskat)abstract
- The accurate determination of species of Cyanoprokaryota/Cyanophyceae has many important applications. These include the assessment of risk with regard to blooms in water reservoirs as well as the identification of species capable of producing valuable bioactive compounds. Commonly, Cyanoprokaryota are classified based on their morphology. However, morphological criteria are not always reliable because they may change, for example, due to environmental factors. Thus, genetic and molecular analyses are a promising additional approach, but their application has so far been limited to relatively few genera. In light of this, we present here the first characterization of species and strains of the genus Phormidium Kutz. based on the cpcB-IGS-cpcA locus of the phycocyanin operon. In phylogenetic analyses using deduced amino acid sequences of the cpcB-cpcA regions, Phormidium was found to be polyphyletic. This analysis appeared to be dominated by the cpcB region, which is characterized by a relatively high percentage of informative substitutions. The percentage of variable positions within the cpcB-IGS-cpcA locus overall was 16.5%, thereby indicating a level of divergence remarkably higher than that reported for Nodularia and Arthrospira in previous studies relying on cpcB-IGS-cpcA. Further, alignment of informative nucleotide substitutions in the cpcB-IGS-cpcA sequences revealed a mosaic distribution, which may be indicative of genetic recombination events. Finally, the length and sequences of the IGS region alone proved useful as markers to differentiate the cyanobacterial genus Phormidium. However, whether the IGS region per se is sufficiently discriminatory to differentiate between Phormidium species or even strains requires further investigation using newly identified Phormidium sequence data.
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| 7. |
- Bergstrom, L., et al.
(författare)
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Genetic and morphological identification of Fucus radicans sp Nov (Fucales, Phaeophyceae) in the brackish Baltic Sea
- 2005
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 41:5, s. 1025-1038
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Tidskriftsartikel (refereegranskat)abstract
- Brown seaweeds of the genus Fucus occupy a wide variety of temperate coastal habitats. The genus is evolutionary dynamic with recent radiations to form morphologically distinct taxa. In the brackish Baltic Sea, fucoids are the only perennial canopy-forming macroalgae. The most northern populations of Fucus occur permanently submerged in extremely low salinity (3-5 psu). These are currently referred to as Fucus vesiculosus L. but are morphologically distinct with a narrow frond without bladders. We report here that a population of this unique morphotype is reproductively isolated from a truly sympatric population of common F. vesiculosus and conclude that the northern morphotype represents a previously undescribed species. We describe Fucus radicans sp. nov., which is attached and dioecious with broadly elliptic receptacles, characterized by a richly branched narrow flat frond (2-5 mm), short thallus (< 26 cm), and a high capacity for vegetative recruitment of attached plants. Analysis of five highly polymorphic microsatellite DNA loci showed genetic differentiation between sympatric populations of F. radicans and F. vesiculosus, whereas allopatric populations of the same species revealed a coherent pattern of genetic variation. Sequences of the RUBISCO region in F. radicans were identical to or differing at only one to two dinucleotide positions from those of F. vesiculosus, indicating a recent common origin of the two species.
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| 8. |
- Corcoll, Natàlia, 1981, et al.
(författare)
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Light History Influences the Response of Fluvial Biofilms to Zn Exposure
- 2012
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 48, s. 1411-1423
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Tidskriftsartikel (refereegranskat)abstract
- Fluvial biofilms are subject to multistress situations in natural ecosystems, such as the co-occurrence of light intensity changes and metal toxicity. However, studies simultaneously addressing both factors are rare. This study evaluated in microcosm conditions the relationship between short-term light intensity changes and Zn toxicity on fluvial biofilms with long-term photoacclimation to different light conditions. Biofilms that had long-term photoacclimation to 25 μmol photons · m-2 · s-1 (low light [LL] biofilms), 100 μmol photons · m-2 · s-1 (medium light [ML] biofilms), and 500 μmol photons · m-2 · s-1 (high light [HL] biofilms) were characterized by different structural (Chlorophyll-a [Chl-a], total biomass-AFDW, EPS, algal groups, and diatom taxonomy) and physiological attributes (ETR-I curves and photosynthetic pigments). HL biofilms showed higher light saturation intensity and a higher production of xanthophylls than LL biofilms. In contrast, LL biofilms had many structural differences; a higher proportion of diatoms and lower AFDW and EPS contents than ML and HL biofilms. A clear effect of light intensity changes on Zn toxicity was also demonstrated. Zn toxicity was enhanced when a sudden increase in light intensity also occurred, mainly with LL biofilms, causing higher inhibition of both the Φ′PSII and the ΦPSII. A decoupling of NPQ from de-epoxidation reaction (DR) processes was also observed, indicating substantial damage to photoprotective mechanisms functioning in biofilms (i.e., xanthophyll cycle of diatoms) due to Zn toxicity. This study highlights the need to take into account environmental stress (e.g., light intensity changes) to better assess the environmental risks of chemicals (e.g., metals). © Phycological Society of America.
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| 9. |
- Elvebakk, Arve, et al.
(författare)
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Phylogenetic patterns among Nostoc cyanobionts within Bi- and tripartite lichens of the genus Pannaria
- 2008
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 44:4, s. 1049-1059
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Tidskriftsartikel (refereegranskat)abstract
- Phylogenetic relationships between Nostoc cyanobionts in the lichen genus Pannaria were studied to evaluate their correlation to geography, habitat ecology, and other patterns previously reported. The 16S rRNA gene sequences of a total of 37 samples of 21 Pannaria species from seven countries from the Northern and Southern hemispheres were analyzed and compared with 69 free-living and symbiotic cyanobacterial strains. The sequences from Pannaria were distributed throughout a branch of Nostoc sequences previously called ""the Nephroma guild,"" and within two subgroups from another branch, referred to as the ""Peltigera guild,"" although there was a gradual transition between the two major groups. There is a more diverse pattern of relationships between Nostoc sequences from bipartite versus tripartite lichen species in Pannaria, compared with other well-studied genera, such as Nephroma and Peltigera. Cyanobionts from several tripartite Pannaria species from the Southern Hemisphere and corticolous bipartite species from both hemispheres were grouped together. Four sequences of Pannaria and Pseudocyphellaria cyanobionts from rocks in the Chilean Juan Fernandez Islands were nested within corticolous cyanobionts, whereas the terricolous ""Pannaria sphinctrina clade"" was placed with other terricolous strains. The cluster patterns derived from phylogenetic analysis were partly reflecting lichen taxonomy, in two groups of lichen species, possibly indicating coevolution. The phylogram partly also reflected lichen ecology. Three Pannaria species have very different cyanobiont strains when they grow in different habitats.
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| 10. |
- Godhe, Anna, 1967, et al.
(författare)
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Comparison of three common molecular tools for distinguishing among geographically separated clones of the diatom Skeletonema marinoi Sarno et Zingone (bacillariophyceae)
- 2006
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 42:2, s. 280-291
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Tidskriftsartikel (refereegranskat)abstract
- Skeletonema marinoi Sarno et Zingone is a planktonic marine diatom with a widespread geographic distribution. Different populations of this species may show distinct genetic signatures. We have evaluated the utility of three common molecular methods for distinguishing clones of S. marinoi from different geographic regions. Clonal cultures were isolated from the Canadian west coast, south west Portugal, and the east and west coasts of Sweden. All strains originated from resting stages in sediment. More than 90% of the individually isolated chains grew to densities suitable for DNA extraction. Genetic signatures of clones from each sample location were assessed by sequencing variable domains (D1-D3) of the nuclear large subunit (LSU) rRNA gene and internal transcriber spacer (ITS) (ITS-1, 5.8S and ITS-2) regions, and also by analysis of randomly amplified polymorphic DNA patterns. Analysis of molecular variance showed that strains from the four geographic areas were significantly separated by all three methods but that differences among European samples were best resolved by ITS 2 sequences.
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