| 1. |
- Hagen, Christoph, et al.
(author)
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Functional aspects of secondary carotenoids in haematococcus lacustris (volvocales). III. Action as a "sunshade"
- 1994
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In: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 30:2, s. 241-248
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Journal article (peer-reviewed)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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| 2. |
- Karlsson-Elfgren, Irene, et al.
(author)
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Recruitment and pelagic growth of Gloeotrichia echinulata (Chyanophyceae) in Lake Erken
- 2003
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In: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 39:6, s. 1050-1056
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Journal article (peer-reviewed)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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| 3. |
- Annenkova, Nataliia V., et al.
(author)
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Delineating closely related dinoflagellate lineages using phylotranscriptomics
- 2018
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In: Journal of Phycology. - : Wiley. - 0022-3646. ; 54:4, s. 571-576
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Journal article (peer-reviewed)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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| 4. |
- Araujo, R., et al.
(author)
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PHENOTYPIC DIFFERENTIATION AT SOUTHERN LIMIT BORDERS: THE CASE STUDY OF TWO FUCOID MACROALGAL SPECIES WITH DIFFERENT LIFE-HISTORY TRAITS
- 2011
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In: Journal of Phycology. - : Wiley. - 0022-3646. ; 47:3, s. 451-462
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Journal article (peer-reviewed)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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| 5. |
- Araujo, R., et al.
(author)
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TRADE-OFFS BETWEEN LIFE-HISTORY TRAITS AT RANGE-EDGE AND CENTRAL LOCATIONS
- 2015
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In: Journal of Phycology. - : Wiley. - 0022-3646. ; 51:4, s. 808-818
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Journal article (peer-reviewed)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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| 6. |
- Bergstrom, L., et al.
(author)
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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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In: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 41:5, s. 1025-1038
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Journal article (peer-reviewed)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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| 7. |
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| 8. |
- Corcoll, Natàlia, 1981, et al.
(author)
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Light History Influences the Response of Fluvial Biofilms to Zn Exposure
- 2012
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In: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 48, s. 1411-1423
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Journal article (peer-reviewed)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.
(author)
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Phylogenetic patterns among Nostoc cyanobionts within Bi- and tripartite lichens of the genus Pannaria
- 2008
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In: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 44:4, s. 1049-1059
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Journal article (peer-reviewed)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. |
- Figueroa, R I, et al.
(author)
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Effects of parental factors and meiosis on sexual offspring of Gymnodinium nolleri (Dinophyceae).
- 2006
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In: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 42:2, s. 350-362
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Journal article (peer-reviewed)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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