| 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
-
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
-
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
-
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
-
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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| 11. |
- Gylle, A. Maria, 1965-, et al.
(författare)
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Fluorescence emission spectra of marine and brackish-water ecotypes of Fucus vesiculosus and Fucus radicans (Phaeophyceae) reveal differences in light-harvesting apparatus : emission spectra in Fucus
- 2011
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 47:1, s. 98-105
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Tidskriftsartikel (refereegranskat)abstract
- The Bothnian Sea in the northerly part of the Baltic Sea is a geologically recent brackish-water environment, and rapid speciation is occurring in the algal community of the Bothnian Sea. We measured low-temperature fluorescence emission spectra from the Bothnian Sea and the Norwegian Sea ecotypes of Fucus vesiculosus L., a marine macroalga widespread in the Bothnian Sea. Powdered, frozen thallus was used to obtain undistorted emission spectra. The spectra were compared with spectra measured from the newly identified species Fucus radicans L.Bergström et L. Kautsky, which is a close relative of F. vesiculosusand endemic to the Bothnian Sea. The spectrum of variable fluorescence was used to identify fluorescence peaks originating in PSI and PSII in this chl c–containing alga. The spectra revealed much higher PSII emission, compared to PSI emission, in the Bothnian Sea ecotype of F. vesiculosus than in F. radicans or in the Norwegian Sea ecotype of F. vesiculosus. The results suggest that more lightharvesting chl a ⁄ c proteins serve PSII in the Bothnian Sea ecotype of F. vesiculosusthan in the two other algal strains. Treatment of the Bothnian Sea ecotype of F. vesiculosusin high salinity (10, 20, and 35 practical salinity units) for 1 week did not lead to spectral changes, indicating that the measured features of the Bothnian Sea F. vesiculosus are stable and not simply a direct result of exposure to low salinity.
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| 12. |
- Johannesson, Kerstin, 1955, et al.
(författare)
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FREQUENT CLONALITY IN FUCOIDS (FUCUS RADICANS AND FUCUS VESICULOSUS; FUCALES, PHAEOPHYCEAE) IN THE BALTIC SEA
- 2011
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 47:5, s. 990-998
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Tidskriftsartikel (refereegranskat)abstract
- Asexual reproduction by cloning may affect the genetic structure of populations, their potential to evolve, and, among foundation species, contributions to ecosystem functions. Macroalgae of the genus Fucus are known to produce attached plants only by sexual recruitment. Recently, however, clones of attached plants recruited by asexual reproduction were observed in a few populations of Fucus radicans Bergstrom et L. Kautsky and F. vesiculosus L. inside the Baltic Sea. Herein we assess the distribution and prevalence of clonality in Baltic fucoids using nine polymorphic microsatellite loci and samples of F. radicans and F. vesiculosus from 13 Baltic sites. Clonality was more common in F. radicans than in F. vesiculosus, and in both species it tended to be most common in northern Baltic sites, although variation among close populations was sometimes extensive. Individual clonal lineages were mostly restricted to single or nearby locations, but one clonal lineage of F. radicans dominated five of 10 populations and was widely distributed over 550 x 100 km of coast. Populations dominated by a few clonal lineages were common in F. radicans, and these were less genetically variable than in other populations. As thalli recruited by cloning produced gametes, a possible explanation for this reduced genetic variation is that dominance of one or a few clonal lineages biases the gamete pool resulting in a decreased effective population size and thereby loss of genetic variation by genetic drift. Baltic fucoids are important habitat-forming species, and genetic structure and presence of clonality have implications for conservation strategies.
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| 13. |
- Johnsen, G, et al.
(författare)
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Eco-physiology, bio-optics and toxicity of the ichthyotoxic prymnesiophyte Chrysochromulina leadbeateri
- 1999
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 35:6, s. 1465-1476
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Tidskriftsartikel (refereegranskat)abstract
- A toxic phytoplankton bloom, dominated by the prymnesiophyte Chrysochromulina leadbeateri Estep, developed in the Ofotfjord-Tysfjord area (North Norway) in mid-May and ended in late June 1991 in Vestfjorden and the adjacent fjord areas, Chrysochromulina leadbeateri dominated at total cell densities of >2 x 10(6) cells . L-1; at lower total cell densities, C. leadbeateri was accompanied by other Chrysochromulina species, peridinin-containing dinoflagellates, and diatoms, Bio-optical characteristics and pigmentation in laboratory and field strains of C. leadbeateri allowed for the interpretation of the optical signatures within the bloom. The bio-optical data suggested healthy and actively growing cells during the bloom. About 600 metric tons of pen-raised Atlantic salmon were killed by the C. leadbeateri bloom. A laboratory study was conducted to assess the potential impact of finfish on C. leadbeaferi growth. It was found that the polyamine putrescine enhanced cell biomass and hemolytic activity. Given this, a possible scenario for the development of this bloom and the level of toxicity is hypothesized: (1) The nutrient loading in the Ofotfjord area was enhanced during the winter of 1990-1991 due to the overwintering of 1.5 x 10(6) metric tons of herring from a depth of 0-250 m, This may have sustained a large stock of the mixotrophic C. leadbeateri in early spring before light regime (irradiance, spectral irradiance, and day length) made net photosynthesis possible, (2) The release of polyamines during; the decay of dead fish (e.g. putrescine, cadaverine, and histamine) may have acted as cofactors with ichthyotoxins making "hypertoxic complexes" with the polyamines enhancing growth in the mixotrophic C, leadbeateri.
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| 14. |
- Kamenos, Nicholas A., et al.
(författare)
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Temperature controls on coralline algal skeletal growth
- 2010
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 46:2, s. 331-335
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Tidskriftsartikel (refereegranskat)abstract
- Many marine and terrestrial organisms lay down regular growth bands. In some species (e.g., trees), control of growth band geometry is related to environmental conditions. Coralline algae are long-lived marine plants with a global distribution that lay down regular calcitic growth bands composed of more- and less-extensively calcified cells. Little is known about environmental and organism controls on their growth. In this investigation, coralline algae (Lithothamnion glaciale Kjellm.) were grown at 8, 11, and 15 degrees C, and temperature controls on algal growth were considered. Calcite density within less-extensively calcified cells in L. glaciale was negatively correlated to summer temperature. No relationships were observed between temperature and calcite density in more-extensively calcified cells or growth-band width itself. Additionally, temperature controls on growth in three L. glaciale thalli over the last 50 years were considered. Temperature was negatively related to calcite density in more- and less-extensively calcified cells but showed no consistent relationship with band width.
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| 15. |
- Karlsson-Elfgren, Irene, et al.
(författare)
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The Importance of Shallow Sediments in the Recruitment of Anabaena and Aphanizomenon (Cyanophyceae)
- 2004
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 40:5, s. 831-836
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Tidskriftsartikel (refereegranskat)abstract
- Recruitment of Anabaena and Aphanizomenon from the sediments to the water column was investigated in shallow (1-2 m) and deep (6-7 m) areas of Lake Limmaren, central Sweden. Recruitment traps attached to the bottom were sampled weekly throughout the summer season (June through September). A comparison between the two sites shows that the largest part of the recruited cells originated from the shallow site, although recruitment occurred at all depths in the lake. There were also differences between the species, regarding the site as well as the timing of the recruitment. The contribution of the inoculum to the pelagic population was calculated to vary between 0.003% and 0.05% for the different species. From these results we conclude that shallow sediments are more important than deep ones for the recruitment and that the inoculum in Lake Limmaren is small but may still be an important factor in the population dynamics.
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| 16. |
- Morgan-Kiss, R M, et al.
(författare)
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The Antarctic psychrophile, Chlamydomonas raudensis Ettl (UWO241) (Chlorophyceae, Chlorophyta), exhibits a limited capacity to photoacclimate to red light
- 2005
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 41:4, s. 791-800
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Tidskriftsartikel (refereegranskat)abstract
- The psychrophilic Antarctic alga, Chlamydomonas raudensis Ettl (UWO241), grows under an extreme environment of low temperature and low irradiance of a limited spectral quality (blue-green). We investigated the ability of C. raudensis to acclimate to long-term imbalances in excitation caused by light quality through adjustments in photosystem stoichiometry. Log-phase cultures of C. raudensis and C. reinhardtii grown under white light were shifted to either blue or red light for 12 h. Previously, we reported that C. raudensis lacks the ability to redistribute light energy via the short-term mechanism of state transitions. However, similar to the model of mesophilic alga, C. reinhardtii, the psychrophile retained the capacity for long-term adjustment in energy distribution between PSI and PSII by modulating the levels of PSI reaction center polypeptides, PsaA/PsaB, with minimal changes in the content of the PSII polypeptide, D1, in response to changes in light quality. The functional consequences of the modulation in PSI/PSII stoichiometry in the psychrophile were distinct from those observed in C. reinhardtii. Exposure of C. raudensis to red light caused 1) an inhibition of growth and photosynthetic rates, 2) an increased reduction state of the intersystem plastoquinone pool with concomitant increases in nonphotochemical quenching, 3) an uncoupling of the major light-harvesting complex from the PSII core, and 4) differential thylakoid protein phosphorylation profiles compared with C. reinhardtii. We conclude that the characteristic low levels of PSI relative to PSII set the limit in the capacity of C. raudensis to photoacclimate to an environment enriched in red light.
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| 17. |
- Papaefthimiou, Dimitra, et al.
(författare)
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Diversity and specificity of Azolla cyanobionts
- 2008
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 44:1, s. 60-70
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Tidskriftsartikel (refereegranskat)abstract
- A unique, hereditary symbiosis exists between the water fern Azolla and cyanobacteria that reside within a cavity in the dorsal leaf-lobe of the plant. This association has been studied extensively, and questions have frequently been raised regarding the number and diversity of cyanobionts (cyanobacterial symbionts) among the different Azolla strains and species. In this work, denaturating gradient gel electrophoresis (DGGE) and a clone library based on the 16S rRNA gene were used to study the genetic diversity and host specificity of the cyanobionts in 35 Azolla strains covering a wide taxonomic and geographic range. DNA was extracted directly from the cyanobacterial packets, isolated after enzymatic digestion of the Azolla leaves. Our results indicated the existence of different cyanobiont strains among Azolla species, and diversity within a single Azolla species, independent of the geographic origin of the host. Furthermore, the cyanobiont exhibited host-species specificity and showed most divergence between the two sections of genus Azolla, Azolla and Rhizosperma. These findings are in agreement with the recent redefinition of the taxon Azolla cristata within the section Azolla. With regard to the taxonomic status of the cyanobiont, the genus Anabaena of the Nostocaceae family was identified as the closest relative by this work.
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| 18. |
- Pocock, Tessa, et al.
(författare)
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Chlamydomonas raudensis Ettl. (UWO241) exhibits the capacity for rapid D1 repair in response to chronic photoinhibition at low temperature
- 2007
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 43:5, s. 924-936
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Tidskriftsartikel (refereegranskat)abstract
- Maximum photosynthetic capacity indicates that the Antarctic psychrophile Chlamydomonas raudensis H. Ettl UWO 241 is photosynthetically adapted to low temperature. Despite this finding, C. raudensis UWO 241 exhibited greater sensitivity to low-temperature photoinhibition of PSII than the mesophile Chlamydomonas reinhardtii P. A. Dang. However, in contrast with results for C. reinhardtii, the quantum requirement to induce 50% photoinhibition of PSII in C. raudensis UWO 241 (50 μmol photons) was comparable at either 8°C or 29°C. To our knowledge, this is the first report of a photoautotroph whose susceptibility to photoinhibition is temperature independent. In contrast, the capacity of the psychrophile to recover from photoinhibition of PSII was sensitive to temperature and inhibited at 29°C. The maximum rate of recovery from photoinhibition of the psychrophile at 8°C was comparable to the maximum rate of recovery of the mesophile at 29°C. We provide evidence that photoinhibition in C. raudensis UWO 241 is chronic rather than dynamic. The photoinhibition-induced decrease in the D1 content in C. raudensis recovered within 30 min at 8°C. Both the recovery of the D1 content as well as the initial fast phase of the recovery of Fv/Fm at 8°C were inhibited by lincomycin, a chloroplast protein synthesis inhibitor. We conclude that the susceptibility of C. raudensis UWO 241 to low-temperature photoinhibition reflects its adaptation to low growth irradiance, whereas the unusually rapid rate of recovery at low temperature exhibited by this psychrophile is due to a novel D1 repair cycle that is adapted to and is maximally operative at low temperature.
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| 19. |
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| 20. |
- Sundström, Annica M., et al.
(författare)
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GYMNODINIUM COROLLARIUM SP. NOV. (DINOPHYCEAE)—A NEW COLD-WATER DINOFLAGELLATE RESPONSIBLE FOR CYST SEDIMENTATION EVENTS IN THE BALTIC SEA
- 2009
-
Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 45, s. 938-952
-
Tidskriftsartikel (refereegranskat)abstract
- A naked dinoflagellate with a unique arrangement of chloroplasts in the center of the cell was isolated from the northern Baltic proper during a spring dinoflagellate bloom (March 2005). Morphological, ultrastructural, and molecular analyses revealed this dinoflagellate to be undescribed and belonging to the genus Gymnodinium F. Stein. Gymnodinium corollarium A. M. Sundström, Kremp et Daugbjerg sp. nov. possesses features typical of Gymnodinium sensu stricto, such as nuclear chambers and an apical groove running in a counterclockwise direction around the apex. Phylogenetic analyses based on partial nuclear-encoded LSU rDNA sequences place the species in close proximity to G. aureolum, but significant genetic distance, together with distinct morphological features, such as the position of chloroplasts, clearly justifies separation from this species. Temperature and salinity experiments revealed a preference of G. corollarium for low salinities and temperatures, confirming it to be a cold-water species well adapted to the brackish water conditions in the Baltic Sea. At nitrogen-deplete conditions, G. corollarium cultures produced small, slightly oval cysts resembling a previously unidentified cyst type commonly found in sediment trap samples collected from the northern and central open Baltic Sea. Based on LSU rDNA comparison, these cysts were assigned to G. corollarium. The cysts have been observed in many parts of the Baltic Sea, indicating the ecologic versatility of the species and its importance for the Baltic ecosystem.
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| 21. |
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| 22. |
- Ulanova, Anna, et al.
(författare)
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Coastal diatom-environment relationships in the brackish Baltic Sea
- 2009
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 45:1, s. 54-68
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Tidskriftsartikel (refereegranskat)abstract
- High-quality calibration data sets are required when diatom assemblages are used for monitoring ecological change or reconstructing palaeo-environments. The quality of such data sets can be validated, in addition to other criteria, by the percentage of significant unimodal species responses as a measure of the length of an environmental gradient. This study presents diatom-environment relationships analyzed from a robust data set of diatom communities living on submerged stones along a 2,000 km long coastline in the Baltic Sea area, including 524 samples taken at 135 sites and covering a salinity gradient from 0.4 to 11.4. Altogether, 487 diatom taxa belonging to 102 genera were recorded. Detrended canonical correspondence analysis showed that salinity was the overriding environmental factor regulating diatom community composition, while exposure to wave action and nutrient concentrations were of secondary importance. Modeling the abundances of the 58 most common diatom taxa yielded significant relationships with salinity for 57 taxa. Twenty-three taxa showing monotonic responses were species with optimum distributions in freshwater or marine waters. Thirty-four taxa showing unimodal responses were brackish-water species with maximum distributions at different salinities. Separate analyses for small (cell biovolume <1,000 μm3) and large (≥1,000 μm3) taxa yielded similar results. In previous studies along shorter salinity gradients, large and small epilithic diatom taxa responded differently. From our large data, we conclude that counts of large diatom taxa alone seem sufficient for indicating salinity changes in coastal environments with high precision.
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| 23. |
- Karlsson-Elfgren, Irene, et al.
(författare)
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Recruitment and pelagic growth of Gloeotrichia echinulata (Chyanophyceae) in Lake Erken
- 2003
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 39:6, s. 1050-1056
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Tidskriftsartikel (refereegranskat)abstract
- Different parameters in the life cycle of the colony forming cyanobacterium Gloeotrichia echinulata (J.E. Smith) Richter was evaluated in Lake Erken, Sweden. Recruitment of colonies from the sediments and pelagic abundance were measured during 2 years. These data were then used in a model to evaluate and estimate parameters of the life cycle. In our study, recruitment alone only contributed to a small part (<5%) of the maximum G. echinulata abundance that occurred during late summer. However, recruitment from shallow sediments forms the important seed for the pelagic population. Together with measured rates of migration from the sediment, variations in either pelagic colony division rate or pelagic residence time could explain variations in the measured abundance of G. echinulata in situ.
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| 24. |
- Haubner, Norbert, et al.
(författare)
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ABIOTIC STRESS MODIFIES THE SYNTHESIS OF ALPHA-TOCOPHEROL AND BETA-CAROTENE IN PHYTOPLANKTON SPECIES
- 2014
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 50:4, s. 753-759
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Tidskriftsartikel (refereegranskat)abstract
- We performed laboratory experiments to investi-gate whether the synthesis of the antioxidants -tocopherol (vitamin E) and -carotene in phytoplankton depends on changes in abiotic factors. Cultures of Nodularia spumigena, Phaeodactylum tricornutum, Skeletonema costatum, Dunaliella tertiolecta, Prorocentrum cordatum, and Rhodomonas salina were incubated at different tempe-ratures, photon flux densities and salinities for 48h. We found that abiotic stress, within natural ecological ranges, affects the synthesis of the two antioxidants in different ways in different species. In most cases antioxidant production was stimulated by increased abiotic stress. In P.tricornutumKAC 37 and D.tertiolectaSCCAP K-0591, both good producers of this compound, -tocopherol accumulation was negatively affected by environmentally induced higher photosystem II efficiency (F-v/F-m). On the other hand, -carotene accumulation was positively affected by higher F-v/F-m in N.spumigena KAC 7, P.tricornutum KAC 37, D.tertiolecta SCCAP K-0591 and R.salina SCCAP K-0294. These different patterns in the synthesis of the two compounds may be explained by their different locations and functions in the cell. While -tocopherol is heavily involved in the protection of prevention of lipid peroxidation in membranes, -carotene performs immediate photo-oxidative protection in the antennae complex of photosystem II. Overall, our results suggest a high variability in the antioxidant pool of natural aquatic ecosystems, which can be subject to short-term temperature, photon flux density and salinity fluctuations. The antioxidant levels in natural phytoplankton communities depend on species composition, the physiological condition of the species, and their respective strategies to deal with reactive oxygen species. Since -tocopherol and -carotene, as well as many other nonenzymatic antioxidants, are exclusively produced by photo-synthetic organisms, and are required by higher trophic levels through dietary intake, regime shifts in the phytoplankton as a result of large-scale environmental changes, such as climate change, may have serious consequences for aquatic food webs.
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| 25. |
- Kahlert, Maria, et al.
(författare)
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Connecting the morphological and molecular species concepts to facilitate species identification within the genus Fragilaria (Bacillariophyta)
- 2019
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 55, s. 948-970
-
Tidskriftsartikel (refereegranskat)abstract
- This paper explores the diversity and taxonomy of species within Fragilaria sensu stricto, an abundant and ecologically important diatom genus, taking advantage of cultured and DNA-barcoded material. The goal is to facilitate the identification of European taxa within this complex, providing a unified view on morphological and molecular diversity. There is a general agreement that the separation of species within the group of Fragilaria is difficult because morphological descriptions of species are not consistent between authorities, ongoing taxonomic revisions have resulted in species described with standards of the late 20th and 21st centuries alongside descriptions based on 19th century (light microscopical) criteria, and because not all diagnostic characters can be seen in all specimens encountered in routine analyses. Consequent confusion could blur potentially important ecological distinctions between species. Our study demonstrated that some species defined on morphological criteria could be confirmed using the rbcL chloroplast gene as a genetic marker, for example, Fragilaria gracilis, Fragilaria tenera, Fragilaria perminuta, and Fragilaria subconstricta. However, even for those species, preliminary identifications based on morphology often differed from identifications based on phylogenetic clustering combined with detailed morphological study. Clades were well-defined by rbcL, but based on morphology, the terminal taxa of these clades did not match the currently described Fragilaria species. To clarify recognition of these taxa, we describe three new species: Fragilaria agnesiae, Fragilaria heatherae, and Fragilaria joachimii.
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| 26. |
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| 27. |
- Lebret, Karen, et al.
(författare)
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Phylogeography of the freshwater raphidophyte Gonyostomum semen confirms a recent expansion in northern Europe by a single haplotype
- 2015
-
Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 51:4, s. 768-781
-
Tidskriftsartikel (refereegranskat)abstract
- Gonyostmum semen is a freshwater raphidophyte that has increased in occurrence and abundance in several countries in northern Europe since the 1980s. More recently, the species has expanded rapidly also in north-eastern Europe, and it is frequently referred to as invasive. To better understand the species history, we have explored the phylogeography of G. semen using strains from northern Europe, United States, and Japan. Three regions of the ribosomal RNA gene (small subunit [SSU], internal transcribed spacer [ITS] and large subunit [LSU]) and one mitochondrial DNA marker (cox1) were analyzed. The SSU and partial LSU sequences were identical in all strains, confirming that they belong to the same species. The ITS region differentiated the American from the other strains, but showed high intra-strain variability. In contrast, the mitochondrial marker cox1 showed distinct differences between the European, American, and Japanese strains. Interestingly, only one cox1 haplotype was detected in European strains. The overall low diversity and weak geographic structure within northern European strains supported the hypothesis of a recent invasion of new lakes by G. semen. Our data also show that the invasive northern European lineage is genetically distinct from the lineages from the other continents. Finally, we concluded that the mitochondrial cox1 was the most useful marker in determining large-scale biogeographic patterns in this species.
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| 28. |
- McCoy, Sophie J., et al.
(författare)
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Coralline algae (Rhodophyta) in a changing world : integrating ecological, physiological, and geochemical responses to global change
- 2015
-
Ingår i: Journal of Phycology. - : John Wiley & Sons. - 0022-3646 .- 1529-8817. ; 51:1, s. 6-24
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Tidskriftsartikel (refereegranskat)abstract
- Coralline algae are globally distributed benthic primary producers that secrete calcium carbonate skeletons. In the context of ocean acidification, they have received much recent attention due to the potential vulnerability of their high-Mg calcite skeletons and their many important ecological roles. Herein, we summarize what is known about coralline algal ecology and physiology, providing context to understand their responses to global climate change. We review the impacts of these changes, including ocean acidification, rising temperatures, and pollution, on coralline algal growth and calcification. We also assess the ongoing use of coralline algae as marine climate proxies via calibration of skeletal morphology and geochemistry to environmental conditions. Finally, we indicate critical gaps in our understanding of coralline algal calcification and physiology and highlight key areas for future research. These include analytical areas that recently have become more accessible, such as resolving phylogenetic relationships at all taxonomic ranks, elucidating the genes regulating algal photosynthesis and calcification, and calibrating skeletal geochemical metrics, as well as research directions that are broadly applicable to global change ecology, such as the importance of community-scale and long-term experiments in stress response.
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| 29. |
- Münzner, Karla, 1989-, et al.
(författare)
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High Iron Requirements for Growth in the Nuisance Alga Gonyostomum semen (Raphidophyceae)
- 2021
-
Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 57:4, s. 1309-1322
-
Tidskriftsartikel (refereegranskat)abstract
- The bloom-forming freshwater alga Gonyostomum semen is associated with acidic, mesotrophic brown water lakes in boreal regions. However, researchers have been unable to conclusively link G. semen abundance and bloom formation to typical brown water lake traits, that is, high water color and DOC (dissolved organic carbon) concentrations. Iron is a main driver of water color in boreal lakes, and a recent study of lake monitoring data indicated a connection between lakes with high G. semen abundance and iron concentrations >200 µg · L−1. Thus, iron may be the missing link in explaining G. semen abundance and growth dynamics. We experimentally assessed the effects of different iron concentrations above or below 200 µg · L−1 on the growth of G. semen batch monocultures. Iron concentrations <200 µg · L−1 limited G. semen growth, while iron concentrations >200 µg · L−1 did not. Moreover, the iron concentration of the medium required for growth was higher than for other common phytoplankton (Microcystis botrys and Chlamydomonas sp.) included in the experiment. These results indicate that G. semen requires high levels of iron in the lake environment. Consequently, this and previous findings using lake monitoring data support the hypothesis that high concentrations of iron favor the formation of high-density G. semen blooms in boreal brown water lakes. As lakes get browner in a changing climate, monitoring iron levels could be a potential tool to identify lakes at risk for G. semen blooms, especially among lakes that provide ecosystem services to society.
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| 30. |
- Persson, Agneta, 1963, et al.
(författare)
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Differences in Specific Mass Density Between Dinoflagellate Life Stages and Relevance to Accumulation by Hydrodynamic Processes
- 2021
-
Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 57:5, s. 1492-1503
-
Tidskriftsartikel (refereegranskat)abstract
- One previously unstudied aspect of differences between sexual and asexual life stages in large-scale transport and accumulation is density (mass per unit volume) of cells in each life stage. The specific density was determined for Scrippsiella lachrymosa cells in medium with and without nitrogen (N) enrichment through density-gradient centrifugation. Growth medium without N addition is often called "encystment medium" when used for the purpose of resting cyst formation in cyst-forming dinoflagellates; mating gametes are usually seen after 2-3 days. Significant differences in specific density were found after 2 days in encystment medium simultaneously with the observation of typical gamete swimming behavior and mating. The specific density of cells in encystment medium was 1.06 g center dot cm(-3); whereas, the specific density of cells in growth medium was 1.11 g center dot cm(-3). Cells in encystment medium were found to have significantly increased lipid content, reduced chlorophyll content, and reduced internal complexity. The findings may explain differential transport of less dense and chemotactically aggregating gametes into surface blooms in contrast to denser vegetative cells that perform daily vertical migration and do not aggregate. Passive accumulation of non-migrating gametes into layers in stagnant water also can be explained, as well as sinking of zygotes when the storage of highly dense starch increases. Resting cysts had a density of over 1.14 g center dot cm(-3) and would sink to become part of the silt fraction of the sediment. We suggest that differences in behavior and buoyancy between sexual and asexual life stages cause differences in cell accumulation, and therefore large-scale, environmental transport could be directly dependent upon life-cycle transitions.
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| 31. |
- Sassenhagen, Ingrid, et al.
(författare)
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Pigment composition and photoacclimation as keys to the ecological success of Gonyostomum semen (Raphidophyceae, Stramenopiles)
- 2014
-
Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 50:6, s. 1146-1154
-
Tidskriftsartikel (refereegranskat)abstract
- Aquatic habitats are usually structured by light attenuation with depth resulting in different microalgal communities, each one adapted to a certain light regime by their specific pigment composition. Several taxa contain pigments restricted to one phylogenetic group, making them useful as marker pigments in phytoplankton community studies. The nuisance and invasive freshwater microalga Gonyostomum semen (Ehrenberg) (Raphidophyceae) is mainly found in brown water lakes with sharp vertical gradients in light intensity and color. However, its pigment composition and potential photoadaptations have not been comprehensively studied. We analyzed the photopigment composition of 12 genetically different strains of G. semen by HPLC after acclimation to different light conditions. We confirmed the pigments chlorophyll a, chlorophyll c1c2, diadinoxanthin, trans-neoxanthin, cis-neoxanthin, α and β carotene, which have already been reported for G. semen. Additionally, we identified, for the first time, the pigments violaxanthin, zeaxanthin and alloxanthin in this species. Alloxanthin has never been observed in raphidophytes before, suggesting differences in evolutionary plastid acquisition between freshwater lineages and the well-described marine species. The amount of total chlorophyll a per cell generally decreased with increasing light intensity. In contrast, the increasing ratios of the prominent pigments diadinoxanthin and alloxanthin per chlorophyll a with light intensity suggest photoprotective functions. Additionally we found significant variation in cell-specific pigment concentration among strains, grouped by lake of origin, which might correspond to genetic differences between strains and populations.
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| 32. |
- Schoenrock, Kathryn M., et al.
(författare)
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Influences of salinity on the physiology and distribution of the Arctic coralline algae, Lithothamnion glaciale (Corallinales, Rhodophyta)
- 2018
-
Ingår i: Journal of Phycology. - : Wiley-Blackwell. - 0022-3646 .- 1529-8817. ; 54:5, s. 690-702
-
Tidskriftsartikel (refereegranskat)abstract
- In Greenland, free-living red coralline algae contribute to and dominate marine habitats along the coastline. Lithothamnion glaciale dominates coralline algae beds in many regions of the Arctic, but never in Godthabsfjord, Greenland, where Clathromorphum sp. is dominant. To investigate environmental impacts on coralline algae distribution, calcification and primary productivity were measured insitu during summers of 2015 and 2016, and annual patterns of productivity in L.glaciale were monitored in laboratory-based mesocosm experiments where temperature and salinity were manipulated to mimic high glacial melt. The results of field and cold-room measurements indicate that both L.glaciale and Clathromorphum sp. had low calcification and photosynthetic rates during the Greenland summer (2015 and 2016), with maximum of 1.225 +/- 0.17 or 0.002 +/- 0.023mol CaCO3.g(-1).h(-1) and -0.007 +/- 0.003 or -0.004 +/- 0.001mg O-2.L-1.h(-1) in each species respectively. Mesocosm experiments indicate L.glaciale is a seasonal responder; photosynthetic and calcification rates increase with annual light cycles. Furthermore, metabolic processes in L.glaciale were negatively influenced by low salinity; positive growth rates only occurred in marine treatments where individuals accumulated an average of 1.85 +/- 1.73mg.d(-1) of biomass through summer. These results indicate high freshwater input to the Godthabsfjord region may drive the low abundance of L.glaciale, and could decrease species distribution as climate change increases freshwater input to the Arctic marine system via enhanced ice sheet runoff and glacier calving.
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| 33. |
- Stamenković, Marija, et al.
(författare)
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Cultivation and Photophysiological Characteristics of Desmids in Moderately Saline Aquaculture Wastewater
- 2021
-
Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 57:3, s. 926-941
-
Tidskriftsartikel (refereegranskat)abstract
- Although desmids typically inhabit freshwater environments characterized by low amounts of nutrients and low salinity, several desmid species have been recorded in eutrophic waters, indicating their adaptation to elevated pollution and conductivity. This study aimed to determine whether desmids could be used for remediation of moderately saline aquaculture wastewater (AWW) from a fish farm situated in the southeast of Sweden. Fourteen desmid strains isolated from different climates (tropical to polar) and trophic conditions (oligotrophic to eutrophic) were cultivated in diluted AWW and we estimated their growth rates, biomass, nutrient removal efficiency, chlorophyll fluorescence parameters and cellular C, N and P quotas. Despite being grown at moderate salinity, unfavourable N:P ratio, and relatively low light/temperature regime the eutrophic strains, Cosmarium humile, Cosmarium laeve and a meso-oligotrophic species Cosmarium impressulum, completely absorbed nitrate and phosphate from AWW media after 7 d, indicating their potential for remediation of fish effluents in colder climates. These species, along with the typical eutrophic species, Cosmarium meneghinii and Staurastrum chaetoceras, had biomass in the range 0.45-1.19 g center dot L-1 while maximum growth rates ranged from 0.36 to 0.51 center dot d(-1), similar to published rates for several fast-growing green microalgae cultivated in various AWW types. Tropical desmids had distinctly high values of saturating irradiance (I-k > 1,000 mu mol photons center dot m(-2) center dot s(-1)), and, along with eutrophic desmids, had high potential electron transport (rETR(max) > 155 rel. units). Hence, the desmids studied demonstrated inherent photophysiological responses corresponding to their climate and trophic origin under the suboptimal growth conditions.
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| 34. |
- Stenow, Rickard, 1993, et al.
(författare)
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Resting Stages of Skeletonema marinoi Assimilate Nitrogen From the Ambient Environment Under Dark, Anoxic Conditions
- 2020
-
Ingår i: Journal of Phycology. - : John Wiley & Sons, Ltd. - 0022-3646 .- 1529-8817. ; 56:3, s. 699-708
-
Tidskriftsartikel (refereegranskat)abstract
- The planktonic marine diatom Skeletonema marinoi forms resting stages, which can survive for decades buried in aphotic, anoxic sediments and resume growth when re-exposed to light, oxygen, and nutrients. The mechanisms by which they maintain cell viability during dormancy are poorly known. Here, we investigated cell-specific nitrogen (N) and carbon (C) assimilation and survival rate in resting stages of three S. marinoi strains. Resting stages were incubated with stable isotopes of dissolved inorganic N (DIN), in the form of 15N-ammonium (NH4+) or -nitrate (NO3?) and dissolved inorganic C (DIC) as 13C-bicarbonate (HCO3?) under dark and anoxic conditions for 2 months. Particulate C and N concentration remained close to the Redfield ratio (6.6) during the experiment, indicating viable diatoms. However, survival varied between <0.1% and 47.6% among the three different S. marinoi strains, and overall survival was higher when NO3? was available. One strain did not survive in the NH4+ treatment. Using secondary ion mass spectrometry (SIMS), we quantified assimilation of labeled DIC and DIN from the ambient environment within the resting stages. Dark fixation of DIC was insignificant across all strains. Significant assimilation of 15N-NO3? and 15N-NH4+ occurred in all S. marinoi strains at rates that would double the nitrogenous biomass over 77?380 years depending on strain and treatment. Hence, resting stages of S. marinoi assimilate N from the ambient environment at slow rates during darkness and anoxia. This activity may explain their well-documented long survival and swift resumption of vegetative growth after dormancy in dark and anoxic sediments.
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| 35. |
- Turk-Kubo, Kendra A., et al.
(författare)
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Distinct ecological niches of marine symbiotic N2-fixing cyanobacterium Candidatus Atelocyanobacterium thalassa sublineages
- 2017
-
Ingår i: Journal of Phycology. - : John Wiley & Sons. - 0022-3646 .- 1529-8817. ; 53:2, s. 451-461
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Tidskriftsartikel (refereegranskat)abstract
- A recently described symbiosis between the metabolically streamlined nitrogen-fixing cyanobacterium UCYN-A and a single-celled eukaryote prymnesiophyte alga is widely distributed throughout tropical and subtropical marine waters, and is thought to contribute significantly to nitrogen fixation in these regions. Several UCYN-A sublineages have been defined based on UCYN-A nitrogenase (nifH) sequences. Due to the low abundances of UCYN-A in the global oceans, currently existing molecular techniques are limited for detecting and quantifying these organisms. A targeted approach is needed to adequately characterize the diversity of this important marine cyanobacterium, and to advance understanding of its ecological importance. We present findings on the distribution of UCYN-A sublineages based on high throughput sequencing of UCYN-A nifH PCR amplicons from 78 samples distributed throughout many major oceanic provinces. These UCYN-A nifH fragments were used to define oligotypes, alternative taxonomic units defined by nucleotide positions with high variability. The data set was dominated by a single oligotype associated with the UCYN-A1 sublineage, consistent with previous observations of relatively high abundances in tropical and subtropical regions. However, this analysis also revealed for the first time the widespread distribution of the UCYN-A3 sublineage in oligotrophic waters. Furthermore, distinct assemblages of UCYN-A oligotypes were found in oligotrophic and coastally influenced waters. This unique data set provides a framework for determining the environmental controls on UCYN-A distributions and the ecological importance of the different sublineages.
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| 36. |
- Annenkova, Nataliia V., et al.
(författare)
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Delineating closely related dinoflagellate lineages using phylotranscriptomics
- 2018
-
Ingår i: Journal of Phycology. - : Wiley. - 0022-3646. ; 54:4, s. 571-576
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Tidskriftsartikel (refereegranskat)abstract
- Recently radiated dinoflagellates Apocalathium aciculiferum (collected in Lake Erken, Sweden), Apocalathium malmogiense (Baltic Sea) and Apocalathium aff. malmogiense (Highway Lake, Antarctica) represent a lineage with an unresolved phylogeny. We determined their phylogenetic relationships using phylotranscriptomics based on 792 amino acid sequences. Our results showed that A. aciculiferum diverged from the other two closely related lineages, consistent with their different morphologies in cell size, relative cell length and presence of spines. We hypothesized that A. aff. malmogiense and A. malmogiense, which inhabit different hemispheres, are evolutionarily more closely related because they diverged from a marine common ancestor, adapting to a wide salinity range, while A. aciculiferum colonized a freshwater habitat, by acquiring adaptations to this environment, in particular, salinity intolerance. We show that phylotranscriptomics can resolve the phylogeny of recently diverged protists. This has broad relevance, given that many phytoplankton species are morphologically very similar, and single genes sometimes lack the information to determine species’ relationships.
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| 37. |
- Araujo, R., et al.
(författare)
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PHENOTYPIC DIFFERENTIATION AT SOUTHERN LIMIT BORDERS: THE CASE STUDY OF TWO FUCOID MACROALGAL SPECIES WITH DIFFERENT LIFE-HISTORY TRAITS
- 2011
-
Ingår i: Journal of Phycology. - : Wiley. - 0022-3646. ; 47:3, s. 451-462
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Tidskriftsartikel (refereegranskat)abstract
- Marginal populations are often geographically isolated, smaller, and more fragmented than central populations and may frequently have to face suboptimal local environmental conditions. Persistence of these populations frequently involves the development of adaptive traits at phenotypic and genetic levels. We compared population structure and demographic variables in two fucoid macroalgal species contrasting in patterns of genetic diversity and phenotypic plasticity at their southern distribution limit with a more central location. Models were Ascophyllum nodosum (L.) Le Jol. (whose extreme longevity and generation overlap may buffer genetic loss by drift) and Fucus serratus L. (with low genetic diversity at southern margins). At edge locations, both species exhibited trends in life-history traits compatible with population persistence but by using different mechanisms. Marginal populations of A. nodosum had higher reproductive output in spite of similar mortality rates at all life stages, making edge populations denser and with smaller individuals. In F. serratus , rather than demographic changes, marginal populations differed in habitat, occurring restricted to a narrower vertical habitat range. We conclude that persistence of both A. nodosum and F. serratus at the southern-edge locations depends on different strategies. Marginal population persistence in A. nodosum relies on a differentiation in life-history traits, whereas F. serratus , putatively poorer in evolvability potential, is restricted to a narrower vertical range at border locations. These results contribute to the general understanding of mechanisms that lead to population persistence at distributional limits and to predict population resilience under a scenario of environmental change.
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| 38. |
- Araujo, R., et al.
(författare)
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TRADE-OFFS BETWEEN LIFE-HISTORY TRAITS AT RANGE-EDGE AND CENTRAL LOCATIONS
- 2015
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646. ; 51:4, s. 808-818
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Tidskriftsartikel (refereegranskat)abstract
- The allocation of resources to different life-history traits should represent the best compromise in fitness investment for organisms in their local environment. When resources are limiting, the investment in a specific trait must carry a cost that is expressed in trade-offs with other traits. In this study, the relative investment in the fitness-related traits, growth, reproduction and defence were compared at central and range-edge locations, using the seaweed Ascophyllum nodosum as a model system. Individual growth rates were similar at both sites, whereas edge populations showed a higher relative investment in reproduction (demonstrated by a higher reproductive allocation and extended reproductive periods) when compared to central populations that invested more in defence. These results show the capability of A. nodosum to differentially allocate resources for different traits under different habitat conditions, suggesting that reproduction and defence have different fitness values under the specific living conditions experienced at edge and central locations. However, ongoing climate change may threaten edge populations by increasing the selective pressure on specific traits, forcing these populations to lower the investment in other traits that are also potentially important for population fitness.
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| 39. |
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| 40. |
- Gylle, Maria, et al.
(författare)
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Fluorescence Emission Spectra of Marine and Brackish Water Ecotypes of Fucus vesiculosus L. and F. radicans sp. Nov. (Phaeophyceae) Reveal Differences in Light Harvesting Apparatus.
- 2011
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Ingår i: European journal of phycology. - : John Wiley & Sons. - 0967-0262 .- 1469-4433 .- 0022-3646. ; 47:1, s. 98-105
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Tidskriftsartikel (refereegranskat)abstract
- The Bothnian Sea in the northerly part of the Baltic Sea is a geologically recent brackish-water environment, and rapid speciation is occurring in the algal community of the Bothnian Sea. We measured low-temperature fluorescence emission spectra from the Bothnian Sea and the Norwegian Sea ecotypes of Fucus vesiculosus L., a marine macroalga widespread in the Bothnian Sea. Powdered, frozen thallus was used to obtain undistorted emission spectra. The spectra were compared with spectra measured from the newly identified species Fucus radicans L.Bergström et L. Kautsky, which is a close relative of F. vesiculosusand endemic to the Bothnian Sea. The spectrum of variable fluorescence was used to identify fluorescence peaks originating in PSI and PSII in this chl c–containing alga. The spectra revealed much higher PSII emission, compared to PSI emission, in the Bothnian Sea ecotype of F. vesiculosus than in F. radicans or in the Norwegian Sea ecotype of F. vesiculosus. The results suggest that more lightharvesting chl a ⁄ c proteins serve PSII in the Bothnian Sea ecotype of F. vesiculosusthan in the two other algal strains. Treatment of the Bothnian Sea ecotype of F. vesiculosusin high salinity (10, 20, and 35 practical salinity units) for 1 week did not lead to spectral changes, indicating that the measured features of the Bothnian Sea F. vesiculosus are stable and not simply a direct result of exposure to low salinity.
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| 41. |
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| 42. |
- McQuoid, Melissa R.
(författare)
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Pelagic and benthic environmental controls on the spatial distribution of a viable diatom propagule bank on the Swedish west coast
- 2002
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Ingår i: Journal of Phycology. - 0022-3646. ; 38:5, s. 881-893
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Tidskriftsartikel (refereegranskat)abstract
- The distribution of viable diatom resting stages in sediments on the Swedish west coast was assessed by the most probable number (MPN) culture technique. Multivariate analyses correlated benthic and pelagic environmental factors to the observed spatial variations in the size and taxonomic composition of the propagule bank. Viable diatom resting stages were plentiful (0.2-4.8 million cells.g(-1) dry weight) and were dominated by the genera Skeletonema, Detonula, Chaetoceros, and Thalassiosira. Size of the propagule bank was primarily related to planktonic biomass (measured as chl a) and was highest in the Orust-Tjorn fjord system. Species composition in this fjord system was dominated by D. confervacea (Cleve) Gran and T. nordenskioeldii Cleve in contrast to stations on the outer coast, which contained more cells of T. minima Gaarder, Asterionellopsis glacialis (Castracane) Round, and Leptocylindrus danicus Cleve. These taxonomic variations were principally influenced by deep water oxygen concentrations and water column stability. Benthic resting cells of S. costatum (Greville) Cleve were abundant all along the coast but showed reduced viability in low oxygen environments. Calculations based on MPN values estimated that resuspension of sediment could provide a sizable inoculum to the plankton, although the development of planktonic blooms will also depend on forces of hydrography and weather. Although benthic resting stages may not be absolutely necessary for survival of all diatoms, these cells may be important in determining species cycles, succession, and the spatial distribution of diatoms.
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| 43. |
- Persson, Agneta, 1963, et al.
(författare)
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Differences in pigmentation between life cycle stages in Scrippsiella lachrymosa (dinophyceae)
- 2016
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646. ; 52:1, s. 64-74
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Tidskriftsartikel (refereegranskat)abstract
- Various life cycle stages of cyst-producing dinoflagellates often appear differently colored under the microscope; gametes appear paler while zygotes are darker in comparison to vegetative cells. To compare physiological and photochemical competency, the pigment composition of discrete life cycle stages was determined for the common resting cyst-producing dinoflagellate Scrippsiella lachrymosa. Vegetative cells had the highest cellular pigment content ( 25.2 +/- 0.5 pg cell-1), whereas gamete pigment content was 22% lower. The pigment content of zygotes was 82% lower than vegetative cells, even though they appeared darker under the microscope. Zygotes of S. lachrymosa contained significantly higher cellular concentrations of beta- carotene ( 0.65 +/- 0.15 pg cell -1) than all other life stages. Photoprotective pigments and the de- epoxidation ratio of xanthophylls- cycle pigments in S. lachrymosa were significantly elevated in zygotes and cysts compared to other stages. This suggests a role for accessory pigments in combating intracellular oxidative stress during sexual reproduction or encystment. Resting cysts contained some pigments even though chloroplasts were not visible, suggesting that the brightly colored accumulation body contained photosynthetic pigments. The differences in pigmentation between life stages have implications for interpretation of pigment data from field samples when sampled during dinoflagellate blooms.
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| 44. |
- Rengefors, Karin, et al.
(författare)
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Environmental and endogenous regulation of cyst germination in two freshwater dinoflagellates
- 1998
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Ingår i: JOURNAL OF PHYCOLOGY. - : PHYCOLOGICAL SOC AMER INC. - 0022-3646. ; 34:4, s. 568-577
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Tidskriftsartikel (refereegranskat)abstract
- The role of excystment in relation to seasonal succession was investigated in two freshwater dinoflagellates, Ceratium hirundinella (O.F. Muller) Dujardin and Peridinium aciculiferum (Lemmermann). Field studies and laboratory experiments were performed to
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| 45. |
- Tesson, Sylvie V.M., et al.
(författare)
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The potential for dispersal of microalgal resting cysts by migratory birds
- 2018
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646. ; 54:4, s. 518-528
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Tidskriftsartikel (refereegranskat)abstract
- Most microalgal species are geographically widespread, but little is known about how they are dispersed. One potential mechanism for long-distance dispersal is through birds, which may transport cells internally (endozoochory) and deposit them during, or in-between, their migratory stopovers. We hypothesize that dinoflagellates, in particular resting stages, can tolerate bird digestion; that bird temperature, acidity, and retention time negatively affect dinoflagellate viability; and that recovered cysts can germinate after passage through the birds’ gut, contributing to species-specific dispersal of the dinoflagellates across scales. Tolerance of two dinoflagellate species (Peridiniopsis borgei, a warm-water species and Apocalathium malmogiense, a cold-water species) to Mallard gut passage was investigated using in vitro experiments simulating the gizzard and caeca conditions. The effect of in vitro digestion and retention time on cell integrity, cell viability, and germination capacity of the dinoflagellate species was examined targeting both their vegetative and resting stages. Resting stages (cysts) of both species were able to survive simulated bird gut passage, even if their survival rate and germination were negatively affected by exposure to acidic condition and bird internal temperature. Cysts of A. malmogiense were more sensitive than P. borgei to treatments and to the presence of digestive enzymes. Vegetative cells did not survive conditions of bird internal temperature and formed pellicle cysts when exposed to gizzard-like acid conditions. We show that dinoflagellate resting cysts serve as dispersal propagules through migratory birds. Assuming a retention time of viable cysts of 2–12 h to duck stomach conditions, cysts could be dispersed 150–800 km and beyond.
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| 46. |
- Uku, Jacqueline, et al.
(författare)
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Characterization and comparison of prokaryotic epiphytes associated with three east African seagrasses
- 2007
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Ingår i: Journal of Phycology. - 0022-3646. ; 43:4, s. 768-779
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Tidskriftsartikel (refereegranskat)abstract
- Prokaryotic epiphytes on leaves of three seagrass species, Thalassodendron ciliatum, Thalassia hemprichii, and Cymodocea rotundata, from two Kenyan coastal sites, Nyali (a high-nutrient site) and Vipingo (a low-nutrient site), were characterized genetically and morphol. Denaturing gradient gel electrophoresis (DGGE) and clone libraries of PCR-amplified 16S rRNA gene fragments were used to study prokaryotes assocd. with these seagrasses. In general, the epiphytic coverage was greater in the high-nutrient site, while the microbial diversity was linked to seagrass species rather than the study sites. Cytophaga-Flavobacteria-Bacteroides (CFB) were assocd. with T. ciliatum and T. hemprichii mainly in the nutrient-poor site, while a-, b-, and g-proteobacteria were assocd. with all three species at the two study sites. Some bacteria phylotypes were closely related to sequences of microorganisms previously recovered from wastewaters or other contaminated sources, indicating the influx of land-based wastes into these coastal lagoon ecosystems. The abundance of potential nitrogen (N2)-fixing cyanobacteria on C. rotundata, particularly in the low-nutrient site, suggested that this assocn. may have been acquired to meet N demands. Unicellular cyanobacteria were dominant and assocd. with C. rotundata and T. hemprichii (with those on T. hemprichii being closely related to cyanobacterial symbiotic species), while T. ciliatum was almost devoid of cyanobacterial assocns. at the same site (Nyali), which suggests specificity in the cyanobacteria-seagrass assocns. The abundance of prokaryotic epiphytes was considered to be linked to water depth and tidal exposure.
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| 47. |
- Underwood, G. J. C., et al.
(författare)
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Short-term effects of UVB radiation on chlorophyll fluorescence, biomass, pigments, and carbohydrate fractions in a benthic diatom mat
- 1999
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Ingår i: Journal of Phycology. - 0022-3646. ; 35:4, s. 656-666
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Tidskriftsartikel (refereegranskat)abstract
- The effects on UVB radiation on a subtidal, cohesive-sediment biofilm dominated by the diatom Gyrosigma balticum (Ehrenberg) Rabenhorst were investigated, Chlorophyll fluorescence parameters (F-v/F-m, phi(PSII)), pigment concentrations, cell densities, and carbohydrate fractions were measured in four treatments (no UVBR, ambient UVBR, +7%, and +15% enhancement with UVBR). Enhanced UVBR was provided by a computer-controlled system directly linked to natural diel UVBR levels, increases in phi(PSII) values in the UVBR-enhanced treatments and a decrease in the steady-state fluorescence yield (F-s) from the surface of the biofilms during the middle and latter part of daily exposure periods suggested that G, balticum responded to enhanced UVBR by migrating down into the sediment. Diatoms in the +15% UVBR treatment also had significantly higher concentrations of beta-carotene after 5 days of treatment, Although G. balticum responded to enhanced UVBR by migration and increased beta-carotene concentrations, significant reduction in maximum quantum yield of PSII (F-v/F-m) and in minimal fluorescence (F-o) and decreases in cell densities occurred after 5 days. Concentrations of different carbohydrate fractions (colloidal carbohydrate, glucan, exopolymers [EPS]) associated with diatom biomass and motility also decreased in the UVBR-enhanced treatments. Short-term responses (migration) to avoid UVBR appear insufficient to prevent longer-term decreases in photosynthetic potential and biofilm carbohydrate concentration and biomass.
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