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| 2. |
- Legrand, Catherine, et al.
(author)
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Allelopathy in phytoplankton – biochemical, ecological and evolutionary aspects
- 2003
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In: Phycologia. - : Informa UK Limited. - 0031-8884 .- 2330-2968. ; 42:4, s. 406-419
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Journal article (peer-reviewed)abstract
- It is considered self-evident that chemical interactions are a component of competition in terrestrial systems, but they are largely unknown in aquatic systems. In this review, we propose that chemical interactions, specifically allelopathy, are an important part of phytoplankton competition. Allelopathy, as defined here, applies only to the inhibitory effects of secondary metabolites produced by one species on the growth or physiological function of another phytoplankton species. A number of approaches are used to study allelopathy, but there is no standard methodology available. One of the methods used is cross-culturing, in which the cell-free filtrate of a donor alga is added to the medium of the target species. Another is to study the effect of cell extracts of unknown constituents, isolated exudates or purified allelochemicals on the growth of other algal species. There is a clear lack of controlled field experiments because few allelochemicals have been identified. Molecular methods will be important in future to study the expression and regulation of allelochemicals. Most of the identified allelochemicals have been described for cyanobacteria but some known toxins of marine dinoflagellates and freshwater cyanobacteria also have an allelochemical effect. The mode of action of allelochemicals spans a wide range. The most common effect is to cause cell lysis, blistering, or growth inhibition. The factors that affect allelochemical production have not been studied much, although nutrient limitation, pH, and temperature appear to have an effect. The evolutionary aspects of allelopathy remain largely unknown, but we hypothesize that the producers of allelochemicals should gain a competitive advantage over other phytoplankton. Finally, we discuss the possibility of using allelochemicals to combat harmful algal blooms (HABs). Allelopathic agents are used for biological control in agriculture, e.g. green manures to control soil diseases in Australia, but they have not yet been applied in the context of HABs. We suggest that phytoplankton allelochemicals have the potential for management of HABs in localized areas.
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| 6. |
- Gylle, A Maria, et al.
(author)
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Desiccation and salinity effects on marine and brackhish Fucus vesiculosus L. (Phaeophyceae).
- 2009
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In: Phycologia. - : Informa UK Limited. - 0031-8884 .- 2330-2968. ; 48:3, s. 156-164
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Journal article (other academic/artistic)abstract
- Ecotypes of Fucus vesiculosus L. from the Norwegian Sea (34 psu, marine ecotype) and Bothnian Sea (5 psu, brackish ecotype) have been compared with respect to the ability to withstand desiccation at different temperatures (0, 10, and 20°C). The aim was also to investigate the importance of salinity and light for the availably energy reserves, osmotic adjustment, and pigment content. The maximum quantum yield of photosystem II photochemistry (Fv/Fm) values revealed that the marine ecotype was more able to resist desiccation. The brackish algae showed a decrease in Fv/Fm as a response to desiccation at all temperatures, but the decrease was most pronounced at 20°C. The brackish ecotype recovered from desiccation within 5 h only when treated at 0°C. When the two ecotypes were treated at different levels of salinity in darkness and light, the results suggested that both salinity and irradiance are main factors in the differences in mannitol content between the two ecotypes. Chlorophyll (Chl) measurements showed 25% higher Chl α and 60% higher Chl c in the brackish ecotype in comparison to the marine ecotype. Darkness had a more pronounced effect on the Chl content than the salinity and initiated an increase in the amount of Chl, especially Chl c in the brackish ecotype.
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| 9. |
- Lundholm, Nina, et al.
(author)
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Buried alive - Germination of up to a century-old marine protist resting stages
- 2011
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In: Phycologia. - : Informa UK Limited. - 0031-8884 .- 2330-2968. ; 50:6, s. 629-640
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Journal article (peer-reviewed)abstract
- report on the survival and germination of up to a century-old marine protist resting stages naturally preserved insediments from Koljö Fjord on the west coast of Sweden. This work has focused on germination of dinoflagellate cysts,but diatom resting stages were also observed. We record the longest known survival of dormant dinoflagellate cells. Weindividually isolated more than 1200 cysts of the three most abundant dinoflagellate taxa: Pentapharsodinium dalei,Lingulodinium polyedrum and Scrippsiella spp. Germination success decreased with core depth, and all successfulgerminations took place within the first 2 wk of incubation. Pentapharsodinium dalei had the highest germination successrate, with a maximum of up to 80% in 28-yr-old sediment, and could successfully germinate from core sediments datedto 1920 ± 12. Scrippsiella spp. cysts with cell contents occurred down to c. 90-yr-old sediment and could germinate fromdown to ca. 40-yr-old sediments, with a maximum germination rate of 50-60% in recent sediments. Cysts of L.polyedrum germinated frequently down to 20 yr and rarely to c. 80 yr, with a maximum of 20-50% germination successin recent sediments. Cyst isolation under cooled conditions rather than at room temperature resulted in a significantlyhigher germination success in P. dalei, while no effect was observed for L. polyedrum. The time elapsed since slicing ofthe core affected survival of L. polyedrum cysts negatively, most likely due to the effect of oxygen. The long-termsurvival potential of benthic resting stages that we report here has important implications, as viable resting stagesaccumulated in bottom sediments can be transported back to the water column by, for example, bioturbation andhuman-mediated sediment dredging. Hence, the sediment may to a higher degree than previously considered play a roleas seed bank. This is important in a changing climate and might have particularly severe impacts in the case of harmful species.
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| 10. |
- Mertens, Kenneth Neil, et al.
(author)
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A review of recent freshwater dinoflagellate cysts: taxonomy, phylogeny, ecology and palaeocology
- 2012
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In: Phycologia. - : Informa UK Limited. - 0031-8884 .- 2330-2968. ; 51:6, s. 612-619
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Research review (peer-reviewed)abstract
- Resting stages (e.g. cysts) play an important role in the life history and ecology of phytoplankton, e.g. the survival, reproduction, genetic recombination, and dispersal of many species. Marine dinoflagellates cysts have been intensively studied by both geologists and biologists, but freshwater cysts have received less attention. There are approximately 350 freshwater dinoflagellate species, and resting cysts have been described for 84 species. We evaluated the descriptions, and we reproduced images for each cyst type. The review highlighted the importance of cyst characters for taxonomy and phylogeny. We suggested that shape, wall ornamentation and possibly the archeopyle and color were important morphological characteristics at the generic level and above. The ecology of freshwater dinoflagellate cysts was reviewed, and the ecological role of cysts was discussed. The potential of freshwater cysts for Quaternary palaeoecological reconstructions was highlighted, revealing that these could serve as useful indicators of temperature, pH and productivity.
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| 11. |
- Rodrigues, Maria Valentina Marin, et al.
(author)
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THESES db : The algae 18S rDNA sequence-structure database for inferring phylogenies
- 2017
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In: Phycologia. - : Informa UK Limited. - 0031-8884 .- 2330-2968. ; 56:2, s. 186-192
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Journal article (peer-reviewed)abstract
- The use of 18S rDNA sequences for inferring phylogenies, in particular for higher taxonomic level analysis, has a long tradition in phycology. Similar to ITS2, the 18S rDNA displays a conserved secondary structure that could be used simultaneously with the primary sequence to increase the amount of information used when inferring phylogenetic relationships. Sequence-structure phylogenetics is already established for ITS2 research. Secondary structures no longer simply guide alignments and trees but are used simultaneously by encoding the sequence-structure information into a 12- letter alphabet. We used the knowledge gathered from the extensive body of ITS2 research regarding sequence-structure phylogenetics and applied it to 18S rRNA data; we present THESES db, the Algae 18S rDNA Sequence-Structure Database (http://mbio-serv2.mbioekol.lu.se/THESESdb), which contains sequences and their individual secondary structures for three major groups of algae (Chlorophyta, Bacillariophyta and Rhodophyta). This database was designed to serve as the starting point for future 18S rDNA sequence-structure based phylogenetic analyses that will eventually extend beyond phycology. One hundred phylogenetic trees generated from 18S sequence-only datasets and from parallel 18S sequence-structure datasets were compared for each taxon analyzed in this study (diatoms, green algae and red algae). Half of the comparisons produced trees with different topologies that frequently related to the status of sister genera. Using the lineage information for each species as listed in GenBank, we determined that the sequence-structure approach resolved a genus as monophyletic, while the sequence-only approach failed to do so in comparisons that comprised 3% of the cases examined. The reverse was true for a total of 8.3% of the comparisons that we generated. Future work, both in our labs and among the broader phycological community, will provide additional data to test the accuracy and robustness of a sequence-structure approach at different taxonomic ranks.
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| 12. |
- Rohrlack, Thomas, et al.
(author)
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Fate of intracellular microcystins in the cyanobacterium Microcystis aeruginosa (Chroococcales, Cyanophyceae)
- 2007
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In: Phycologia. - : Informa UK Limited. - 0031-8884 .- 2330-2968. ; 46:3, s. 277-283
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Journal article (peer-reviewed)abstract
- The aim of the present study was to evaluate the importance of microcystin loss processes in cells of Microcystis aeruginosa, either as export from the cells or intracellular breakdown, and to draw conclusions about the function of microcystins to their producers. By supplying radioactive inorganic carbon to M. aeruginosa cultures and suppressing a considerable production of radioactive microcystin after a certain period of time, an intracellular pool of labelled microcystin was built up. The fate of this pool was studied by following its radioactivity in different time-course experiment. No evidence for losses from the intracellular microcystin pool could be found. All radioactive carbon that had been incorporated into microcystin molecules remained in the intracellular microcystin pool irrespective of whether the cyanobacterial cells were subjected to low light or high light. This suggests that under the conditions tested here, microcystins are not subjects of significant loss processes such as export from the cells or intracellular breakdown. The present study therefore failed to produce evidence for an involvement of microcystins in quorum sensing, defence against epiphytic organisms, or other functions requiring an export of the compounds into the surrounding medium. The lack of an intracellular breakdown suggests that microcystins are not involved in metabolic cellular processes.
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| 15. |
- Alfonso, B., et al.
(author)
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Tracing genetic variation of Gelidium canariense (Rhodophyta) based on new and historical collections
- 2023
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In: Phycologia. - 0031-8884. ; 62:4, s. 383-390
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Journal article (peer-reviewed)abstract
- Genetic sequencing of herbarium specimens provides invaluable information on species genetic history. However, several factors hinder the extraction of high-quality DNA from long-term preserved specimens. Our goal was to study the genetic variability of the endemic and habitat-forming macroalga Gelidium canariense over the last 40 years using the mitochondrial intergenic marker cox2-3 spacer. We also studied the genetic diversity at the mesoscale (<100 km), i.e. between two localities on the north coast of Tenerife and at the macroscale (>100 km) using specimens collected on the island of La Palma. We found the presence of the same haplotype at the same location for the last 40 years. This haplotype also coincided within populations of Puerto de la Cruz and Garachico (Tenerife Island) and between populations of different islands (Tenerife and La Palma). This study provides a baseline (i.e. extraction method, PCR protocol for cox2-3 spacer molecular marker, level of DNA degradation of herbarium samples) of the genetic characterization of G. canariense that can be used in future molecular studies to better understand the distribution of genetic diversity in this vulnerable species.
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| 16. |
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| 17. |
- Cronberg, Gertrud
(author)
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The life cycle of Gonyostomum semen (Raphidophyceae)
- 2005
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In: Phycologia. - 0031-8884. ; 44:3, s. 285-293
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Journal article (peer-reviewed)abstract
- Gonyostomum semen (Raphidophyceae) is today one of the most common flagellates in humic lakes ill Sweden and appears regularly in 30% of these lakes. The first mass development of this alga was recorded in 1948 in Lake Helgasjon, South Sweden. In this paper the life cycle of Gonyostomum is described for the first time. During the winter Gonyostomum survived as resting cysts on the surface of the bottom sediment. In spring (April to May) meiosis took place in the cysts, and on excystment two haploid gametes appeared. After a period of mobility, the gametes formed pairs. The gametes then fused, and a new diploid Gonyostomum cell developed. The vegetative stage of Gonyostomum, which was seen during the summer period (May-October), is thus the diploid phase. During this period normal, longitudinal cell division took place. Under unfavourable conditions, temporary cysts Could be formed. Cyst formation started from the centre of the cell, which swelled and became spherical. This was a thin-walled, temporary cyst, which was mobile and, like ordinary cells, had one flagellum protruding forward and one trailing behind. The temporary cysts could accumulate and settle in large clusters where the flagella were lost or had become invisible. When favourable conditions reappeared, the temporary cysts divided and formed two new gametes. In autumn, when the water temperature decreased to below about 10 degrees C, the temporary cysts went into dormancy and became resting cysts. The cyst wall thickened, and a brown body appeared within the cyst. Below 4-6 degrees C no vegetative cells were found.
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| 18. |
- Ellegaard, M., et al.
(author)
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The species concept in a marine diatom: LSU rDNA-based phylogenetic differentiation in Skeletonema marinoi/dohrnii (Bacillariophyceae) is not reflected in morphology
- 2008
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In: Phycologia. - : Informa UK Limited. - 0031-8884. ; 47:2, s. 156-167
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Journal article (peer-reviewed)abstract
- The ubiquitous marine diatom genus Skeletonema includes several newly described species. This paper presents a study of morphology and LSU sequence diversity of one of these new species, Skeletonema marinoi. The 15 monoclonal strains (from the Swedish west coast, the Swedish east coast, Portugal and Canada) included in the study showed differences in LSU rDNA sequence within the morphospecies, with differences seen even among clones established from a single plankton net sample. Morphologically, all clones were indistinguishable from each other and from the closely related species Skeletonema dohrnii. In the original description of these two species, they were differentiated by the structure of the girdle bands. However, the girdle band types of both species were found within single samples of almost all clones of S. marinoi in this study. The LSU-based phylogeny is consistent with the split into two species, and there may be a difference in their bioaeoszraphical distribution. We therefore do not at present suggest that the two species be merged. Questions regarding species delimitation and cryptic species within protists often arise from such studies that include data from both morphological and DNA sequence analysis, and such questions are addressed here.
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| 21. |
- Pavia, Henrik, 1964, et al.
(author)
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Intraspecific variation in the phlorotannin content of the brown alga Ascophyllum nodosum
- 2003
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In: Phycologia. - 0031-8884. ; 42:4, s. 378-383
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Journal article (peer-reviewed)abstract
- Many brown macroalgae contain substantial concentrations of polyphenolic compounds, known as phlorotannins. Previous studies have shown that much of the variation in phlorotannin concentration is correlated with taxonomy and biogeography, but little is known about patterns of variation within species and populations. In this study, we examined intraspecific variation in the phlorotannin content of the intertidal seaweed Ascophyllum nodosum, by testing for differences within as well as between genetic individuals (genets) and populations, and between algal tissues of similar age from juveniles and adults. The results show that variation in the phlorotannin content of annual shoots within primary shoots and genets contributes substantially to the total intraspecific variation. This pattern probably indicates that the phlorotannin content is a highly plastic trait that can be significantly influenced by small-scale variation in extrinsic factors. There were also significant differences in mean phlorotannin content among study sites, and these differences varied significantly between the two study years. The extensive variation within and among genetic individuals and populations shows that it is crucial to use proper sampling designs in field studies comparing phlorotannin levels between different populations, taxa, or experimental treatments, in order to avoid false conclusions. Phlorotannin levels were significantly higher in adult annual tissue than in juveniles in five of six sites, with an overall mean phlorotannin content of 7.8% of dry mass for adult tissue and 5.9% of dry mass for juveniles. This result may be explained by a trade-off between growth and phlorotannin production and a lower mortality risk for larger individuals, leading to a strategy where it is more advantageous for a juvenile to invest in growth than to allocate resources to chemical defence.
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| 23. |
- Rehnstam-Holm, Ann-Sofi, 1959, et al.
(author)
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Molecular studies of Dinophysis (Dinophyceae) species from Sweden and North America
- 2002
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In: Phycologia. - 0031-8884. ; 41:4, s. 348-357
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Journal article (peer-reviewed)abstract
- Diarrhoeic, shellfish poisoning has increasingly become 4 Problem throughout the world. Because the causative organisms Dinophysis spp. cannot be cultured in the laboratory, new approaches are needed to obtain ecological and physiological information. In this study, a acuminata, D. norvegica and D, acuta were collected directly from field samples and used in polymerase chain reactions. The D1-D2 region of the large-subunit ribosomal RNA gene was amplified, cloned and sequenced. Sequence analyses showed that D. acuminata and D, norvegica were nearly identical (> 99%), and that D. acuminata showed an intraspecies variation of 0.8% The D. acuta sequence was 98.7% similar to that of D. acuminata. The slight differences between D. norvegica and D. acuminata suggest that they may have evolved into separate species rather recently. Phylogenetic analyses show that species within the Dinophysiales order should be included in the 'GPP complex', a lineage associated with a diverse array of taxa within the orders Gymnodiniales, Prorocentrales and Peridiniales. The Prorocentrales and Dinophysiales would be sister groups within the GPP complex. Amplification of Swedish D, acuminata isolates always resulted in a single LSU rDNA fragment. In contrast, amplification of the North American D. acuminata always produced two distinct fragments, The longer (735 bp) fragment showed 99.3-100% homology among all sequenced clones of different D. acuminata field isolates. The shorter gene fragment had a 70 bp deletion, but it was otherwise highly homologous to the larger gene fragment, This fragment is possibly a pseudogene and might be an important genetic marker. A variable region that is suitable as a target for a probe to identify, Dinophysis was also identified, Dinopkysis g specificity was confirmed for the probe, in that hybridization to cultured representatives of dinoflagellates and environmental samples containing mixed phytoplankton assemblages resulted in specific labelling of D. acuminata, D. norvegica and D, acuta, but not other dinoflaggellates, No labelling of D. rotundata was observed.
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| 24. |
- Roleda, Michael Y., et al.
(author)
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Susceptibility of spores of different ploidy levels from Antarctic Gigartina skottsbergii (Gigartinales, Rhodophyta) to ultraviolet radiation
- 2008
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In: Phycologia. - 0031-8884. ; 47:4, s. 361-370
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Journal article (peer-reviewed)abstract
- Haploid tetraspores and diploid carpospores from Antarctic Gigartina skottsbergii were exposed in the laboratory to photosynthetically active radiation (400-700 nm = P), P + ultraviolet (UV)-A radiation (320-700 nm = PA) and P + UV-A + UV-B radiation (280-700 nm = PAB). Photosynthetic performance, DNA damage and repair, spore mortality, and an initial characterization of the UV-absorbing mycosporine-like amino acids (MAAs) were studied. Rapid photosynthesis vs irradiance (E) curves of freshly released spores showed that both tetraspores and carpospores were low-light adapted (E-k = 44 +/- 2 and 54 +/- 2 mu mol photons m(-2) s(-1), respectively). The light-harvesting and photosynthetic conversion efficiencies were similar (alpha = 0.13), whereas photosynthetic capacity in terms of optimum quantum yield (F-v/F-m) and relative electron transport rate (rETR(max)) were significantly higher in carpospores. Photoinhibition and recovery of photosynthesis were not significantly different between spore ploidy but were significantly affected by radiation and exposure time treatments. Accumulation of DNA damage was UV-B dose dependent and significantly higher in tetraspores than in carpospores. After 2 days postcultivation, DNA lesions were completely repaired in spores exposed to UV-B dose less than 1.2 X 10(4) J m(-2). The dynamic recovery of photosynthetic capacity as well as effective DNA repair mechanism contributed to the relatively low spore mortality (4-14%). A substantial amount of UV-screening MAAs shinorine and palythine were observed for the first time in spores of Gigartinales. This study on stress and physiological characterization of seaweed propagules is important to understand recruitment dynamics and life history phase dominance in the field.
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