Showing papers in "European Journal of Phycology in 2014"
TL;DR: There is a need for research to determine how changes in the partitioning of primary production between dissolved and particulate phases will have bottom-up effects on ecosystem structure and function and how these changes affect the fate of organic matter in the ocean.
Abstract: The partitioning of organic matter (OM) between dissolved and particulate phases is an important factor in determining the fate of organic carbon in the ocean. Dissolved organic matter (DOM) release by phytoplankton is a ubiquitous process, resulting in 2–50% of the carbon fixed by photosynthesis leaving the cell. This loss can be divided into two components: passive leakage by diffusion across the cell membrane and the active exudation of DOM into the surrounding environment. At present there is no method to distinguish whether DOM is released via leakage or exudation. Most explanations for exudation remain hypothetical; as while DOM release has been measured extensively, there has been relatively little work to determine why DOM is released. Further research is needed to determine the composition of the DOM released by phytoplankton and to link composition to phytoplankton physiological status and environmental conditions. For example, the causes and physiology of phytoplankton cell death are poorly und...
299 citations
TL;DR: These recent developments in DNA-based species delimitation methods are reviewed, and it is discussed how they have changed and continue to change the authors' understanding of algal species boundaries.
Abstract: Given the problems of species delimitation in algae using morphology or sexual compatibility, molecular data are becoming the standard for delimiting species and testing their traditional boundaries. The idea that species are separately evolving metapopulation lineages, along with theoretical progress in phylogenetic and population genetic analyses, has led to the development of new methods of species delimitation. We review these recent developments in DNA-based species delimitation methods, and discuss how they have changed and continue to change our understanding of algal species boundaries. Although single-locus approaches have proven effective for a first rapid and large-scale assessment of species diversity, species delimitation based on single gene trees falls short due to gene tree–species tree incongruence, caused by confounding processes like incomplete lineage sorting, trans-species polymorphism, hybridization and introgression. Data from unlinked loci and multi-species coalescent methods, whic...
290 citations
TL;DR: This report is the first to use solely molecular criteria to distinguish cryptic species of cyanobacteria using molecular characters in the genus Oculatella from all four soil taxa.
Abstract: A total of 27 strains of Oculatella were isolated, characterized and sequenced, and analysed phylogenetically with an additional environmental clone from the Atacama Desert and 10 strains isolated and sequenced by others. The strains were clearly separated based upon phylogenetic analyses conducted with a concatenated alignment of the 16S rRNA and 16S-23S ITS region of the ribosomal operons in the genus Oculatella. Differences in secondary structure of the conserved domains of the ITS region, as well as comparative analysis of P-distance among ITS regions, served to separate the strains into distinct taxonomic units. Seven new species of Oculatella were described, including four from arid to semi-arid soils (O. atacamensis, O. mojaviensis, O. coburnii, O. neakameniensis) and three from more mesic habitats, including a temperate lake (O. hafneriensis), a desert waterfall (O. cataractarum) and a Hawaiian sea cave (O. kauaiensis). The soil forms show statistically significant morphological differences, but t...
129 citations
TL;DR: Evidence of growth optimization of phosphate-deficient C. raciborskii to short-term nutrient fluctuations is found, revealing its physiological flexibility and may help to explain the invasive success of this diazotrophic cyanobacterium in a wide range of aquatic ecosystems where phosphorus is frequently the limiting resource.
Abstract: The role of ecophysiological traits in the success and expansion of the toxic cyanobacterium Cylindrospermopsis raciborskii is still under debate. One key factor appears to be the high physiological flexibility of this organism when obtaining limiting resources. Recent studies have found that filamentous bloom-forming cyanobacteria are able to optimize their growth by adjusting phosphate uptake during fluctuating nutrient conditions. We investigated the growth response of two phosphate-deficient C. raciborskii isolates (MVCC19 from Uruguay and CCMP1973 from USA) to short-term fluctuations in phosphate supply. These isolates were exposed to five phosphate concentrations which were provided in two supply modes: a single pulse (SingleP) versus the same amount divided in 10 pulses (TenP), with one pulse applied every 6 min. Morphological traits and changes in chlorophyll a and phycocyanin fluorescence were also evaluated. Growth rates of CCMP1973 and MVCC19 almost doubled and tripled, respectively, when expos...
54 citations
TL;DR: This study shows for the first time that an alternative system is utilized by cyanobacteria associated with fungi, and could allow them to colonize a wider array of environments, including habitats characterized by low temperature and trace metal availability.
Abstract: In past decades, environmental nitrogen fixation has been attributed almost exclusively to the action of enzymes in the well-studied molybdenum-dependent nitrogen fixation system. However, recent evidence has shown that nitrogen fixation by alternative pathways may be more frequent than previously suspected. In this study, the nitrogen fixation systems employed by lichen-symbiotic cyanobacteria were examined to determine whether their diazotrophy can be attributed, in part, to an alternative pathway. The mining of metagenomic data (generated through pyrosequencing) and PCR assays were used to determine which nitrogen-fixation systems are present in cyanobacteria from the genus Nostoc associated with four samples from different geographical regions, representing different lichen-forming fungal species in the genus Peltigera. A metatranscriptomic sequence library from an additional specimen was examined to determine which genes associated with N2 fixation are transcriptionally expressed. Results indicated t...
48 citations
TL;DR: The ESCA index may represent a useful tool for monitoring programmes in coastal waters, since it has been developed in compliance with the Water Framework Directive; it synthesizes complex information in a simple and reliable way; and its application is simple and cost-effective.
Abstract: This paper presents a new biotic index (ESCA, Ecological Status of Coralligenous Assemblages), based on analyses of in situ records of coralligenous macroalgal assemblages in the Mediterranean Sea. The ESCA index was developed on the basis of previous impact evaluation studies carried out by traditional destructive methods. It was validated on an independent dataset collected during a 3-year study carried out at five localities in the north-western Mediterranean, and tested on a gradient of anthropogenic stressors. Assemblage descriptors selected as metrics of the ESCA index were: (a) presence/absence and abundance of sensitive taxa/groups (expressed as sensitivity level of assemblages, SL), (b) diversity of assemblages (expressed as α-diversity) and (c) heterogeneity of assemblages (expressed as β-diversity). The three metrics were combined to give a final value for the multimetric ecological index, Ecological Quality Ratio, calculated as the ratio between the measured values and the value obtained in th...
47 citations
TL;DR: Morphometric analyses of siliceous scales led to the significant phenotypic differentiation of all four newly described species, and their separation from other related species of the S. petersenii complex is described.
Abstract: The Synura petersenii species complex represents a common, cosmopolitan and highly diverse taxon of autotrophic freshwater flagellates. In this paper, we describe and characterize four new species (S. borealis, S. heteropora, S. hibernica and S. laticarina) that have been identified during our extensive sampling of freshwater habitats in 15 European countries. Morphometric analyses of siliceous scales led to the significant phenotypic differentiation of all four newly described species, and their separation from other related species of the S. petersenii complex. Two of these newly described species (S. hibernica and S. borealis) can be clearly distinguished by characteristic large colonies consisting of elongated, lanceolate-shaped cells. Development of strongly elongated, narrow cells in S. hibernica could be explained by the adaptation of this species to oligotrophic conditions. Though morphologically distinct, S. borealis possesses an exceptionally high degree of genetic diversity, possibly indicating...
37 citations
TL;DR: Results indicate that two hormones combined exert more effective growth stimulation than a single hormone or three, four or five different hormones combined.
Abstract: The main objective of this study was to determine the optimal concentrations of a wide spectrum of exogenous phytohormones for effective stimulation of cell division and production of maximum cell yield in Euglena gracilis Klebs cultured in vitro. Results indicate that two hormones combined exert more effective growth stimulation than a single hormone or three, four or five different hormones combined. Specifically, trans-zeatin at 10−7 M combined with abscisic acid at 10−9 M produced optimal conditions for growth, yielding the maximum cell concentration. High concentrations of exogenous phytohormones were toxic to Euglena. The addition of trans-zeatin, N6-isopentenyladenine, and benzylaminopurine to Euglena cultures resulted in dense, dark green chloroplasts, suggesting that exogenous phytohormones increased the production of chlorophyll. Given the response to exogenous growth regulators, the study identified and quantified the types of endogenous cytokinins (CKs) and abscisic acid (ABA) synthesized in v...
32 citations
TL;DR: Extracellular polymeric substances (EPS) are an important trait of most cyanobacteria, including A. platensis, which possessed a thick and smooth layer of EPS around the spiral trichomes and exhibited high diversity.
Abstract: Arthrospira platensis is a cyanobacterium known for its nutritional value and secondary metabolites Extracellular polymeric substances (EPS) are an important trait of most cyanobacteria, including A platensis Here, we extracted and analysed different fractions of EPS from a locally isolated strain of A platensis Three different fractions of EPS were distinguished These were EPS released into the medium (REPS), EPS loosely bound to the organism (LEPS) and EPS tightly bound to the organism (TEPS), which were extracted by different procedures The LEPS fraction was smaller than the other two fractions The EPS of A platensis exhibited high diversity Total protein and carbohydrate content was determined in each of these fractions The largest amount of total carbohydrates and total proteins was in the TEPS fraction Eight sugar moieties were detected and analysed in all EPS fractions using HPAE-PAD Fructose, mannose and ribose were rare sugar residues in all fractions of EPS With the exception of fr
28 citations
TL;DR: In this article, the authors investigated the differences in cell wall morphology and ultrastructure between two closely related genera, Interfilum and Klebsormidium, and found that the morphological differences are mainly due to the fates of the parental wall after cell division and detachment.
Abstract: Representatives of the closely related genera, Interfilum and Klebsormidium, are characterized by unicells, dyads or packets in Interfilum and contrasting uniseriate filaments in Klebsormidium. According to the literature, these distinct thallus forms originate by different types of cell division, sporulation (cytogony) versus vegetative cell division (cytotomy), but investigations of their morphology and ultrastructure show a high degree of similarity. Cell walls of both genera are characterized by triangular spaces between cell walls of neighbouring cells and the parental wall or central space among the walls of a cell packet, exfoliations and projections of the parental wall and cap-like and H-like fragments of the cell wall. In both genera, each cell has its individual cell wall and it also has part of the common parental wall or its remnants. Therefore, vegetative cells of Interfilum and Klebsormidium probably divide by the same type of cell division (sporulation-like). Various strains representing different species of the two genera are characterized by differences in cell wall ultrastructure, particularly the level of preservation, rupture or gelatinization of the parental wall surrounding the daughter cells. The differing morphologies of representatives of various lineages result from features of the parental wall during cell separation and detachment. Cell division in three planes (usual in Interfilum and a rare event in Klebsormidium) takes place in spherical or short cylindrical cells, with the chloroplast positioned perpendicularly or obliquely to the filament (dyad) axis. The morphological differences are mainly a consequence of differing fates of the parental wall after cell division and detachment. The development of different morphologies within the two genera mostly depends on characters such as the shape of cells, texture of cell walls, mechanical interactions between cells and the influence of environmental conditions.
28 citations
TL;DR: In this paper, sequence data from the DNA barcode COI-5P for 114 samples from the southeastern coast of Brazil, indicated the occurrence of six species of Hypnea.
Abstract: The red algal genus Hypnea (Gigartinales) has a wide geographical distribution along tropical and subtropical coasts around the world. The relatively simple and plastic morphology, often influenced by the conditions of its habitat, complicates the identification of Hypnea species. Therefore, the number and status of some species remain in doubt. Molecular studies have been performed to supplement traditional studies based on morphology, mainly for Hypnea species occurring in Asia. In the present study, sequence data from the DNA barcode COI-5P for 114 samples from the southeastern coast of Brazil, indicated the occurrence of six taxa. Additionally, sequence data from the UPA and rbcL markers for representatives of each of those taxa confirmed the existence of six different species. After morphological analysis and comparison with sequences available in GenBank, these species were named as follows: H. aspera, H. cervicornis, H. cf. musciformis, H. spinella, and two new species, H. flava Nauer, Cassano & M....
TL;DR: It was found that the elimination of UV-A radiation increased chlorophyll a content of the cells, and panels coated with the wavelength shifter layer exhibited 74% and 45% increase in biomass productivity during the same culture period.
Abstract: This study investigates the spectral shifting of UV-A radiation, using fluorescent material, as a tool for enhancing Chlorella sp. growth rate in simulated photobioreactors made of UV-stabilized polycarbonate (PC) and poly (methyl methacrylate) (PMMA). The feasibility of using a fluorescent coating as a wavelength shifter layer, to shift UV-A radiation to the PAR range, was explored. For this purpose, a variety of concentrations of fluorescent dye dissolved in thermoplastic acrylic resin were prepared and used to coat PMMA and PC sheets which then were placed between the radiation source and the culture flask. Compared with the uncoated sheets, the panels coated with the wavelength shifter layer exhibited 74% and 45% (for PC and PMMA substrates, respectively) increase in biomass productivity during the same culture period. It was also found that the elimination of UV-A radiation increased chlorophyll a content of the cells.
TL;DR: A high level of temporal variability is suggested in induced anti-herbivory traits of F. vesiculosus and increased expression of genes with putative defensive functions in conjunction with the reallocation of resources from primary to secondary metabolism is revealed.
Abstract: This study aimed to reveal the dynamics of inducible anti-herbivory traits in the brown seaweed Fucus vesiculosus, in response to grazing by the isopod Idotea baltica. As the molecular basis of defence induction in seaweeds is poorly understood, a transcriptomic approach was used to gain insight into cellular processes underlying defence induction and thus promote the mechanistic understanding of anti-herbivory responses in seaweeds. In a 27 day feeding-assayed induction experiment, temporal patterns of the induced anti-herbivory resistance of F. vesiculosus were assessed under laboratory conditions. Feeding assays were performed at three day intervals, using fresh and reconstituted food. Microarray hybridizations investigating the expression of genes 3 days before, as well as at the same time as, feeding assays revealed a decreased palatability of previously grazed F. vesiculosus pieces compared with non-grazed control pieces. Despite permanent exposure to grazers, F. vesiculosus palatability varied over time. Non-grazed F. vesiculosus pieces were significantly preferred to grazed pieces after 18 and again after 27 days of previous grazing, while their relative palatability for isopods was comparable at all other times during the experiment. Relative to controls, 562/402 genes were ≥ 1.5-fold up-/down-regulated in seaweed pieces that were grazed for 18 days, i.e. when induction of defences was detected in feeding assays. Massive reprogramming of the regulatory expression orchestra (translation, transcription) as well as up-regulation of genes involved in lipid and carbohydrate metabolism, intracellular trafficking, defence and stress response was found. At the same time, down-regulation of photosynthesis was observed in grazed seaweed pieces. This study suggests a high level of temporal variability in induced anti-herbivory traits of F. vesiculosus and reveals increased expression of genes with putative defensive functions in conjunction with the reallocation of resources from primary to secondary metabolism.
TL;DR: It is suggested that temperature change is one of the key factors influencing pellicle formation, preserving viability at low temperature (i.e. 13°C) and developmental changes during reversal of temporary cysts to motile forms were also observed to cause breaks in the cell covering that could serve as sites for bacterial entry.
Abstract: Pellicle or temporary cysts of Pyrodinium bahamense var. compressum (Bohm) Steidinger, Tester & F.J.R. Taylor and their role in bloom dynamics have not yet been adequately characterized and understood. We investigated the role of temperature- and nutrient-mediated stress as factors that could induce pellicle formation in batch cultures. Cellular features and their implications for temporary cyst viability were examined using confocal laser scanning microscopy (CLSM). Our data suggest that temperature change is one of the key factors influencing pellicle formation, preserving viability at low temperature (i.e. 13°C). Hypnocysts (resting cysts) were not observed. During pellicle formation, motile cells generally undergo ecdysis, extrusion of cytoplasmic materials and bacteria, compaction of the nucleus and non-motility. The outermost covering of the temporary cysts shows red autofluorescence and it contains lower concentrations of chlorophyll (chl) a and no detectable chl c. The nuclear region is surrounded...
TL;DR: The results strongly suggest that, in the absence of light, upward vertical migration of benthic diatoms is mostly guided by negative gravitaxis, supporting the often hypothesized capacity of these cells to sense and use gravity to move vertically within the sediment.
Abstract: Vertical migration by diatoms is a well-known phenomenon, occurring in intertidal and subtidal benthic biofilms. It is partially endogenously driven, as cell movements can be observed in the absence of external stimuli such as light, temperature or water cover. Although vertical migration of diatoms under constant conditions has often been attributed to geotactic orientation, this hypothesis has never been experimentally demonstrated. Our study tested the gravitactic nature of the vertical migratory behaviour of benthic diatoms in sedimentary biofilms, using an experimental setup designed to distinguish gravitaxis from surface-oriented cell movements. The hourly variation of surface diatom biomass during migratory cycles was compared in homogenized sediment samples kept facing upwards (surface-oriented and gravity stimuli coinciding; controls) and facing sideways or downwards (surface-oriented and gravity stimuli not coinciding). During the experiments, sediment samples were kept in complete darkness in c...
TL;DR: The samples taken from oak trees were more diverse in their OTU composition than those taken from pine trees, but the average phylogenetic distances of OTUs in samples did not differ between the host tree taxa, indicating that habitat filtering is important for the distribution of individual microalgal phylogenetic taxa.
Abstract: Green algae in corticolous biofilms are simple coccoid cells or filamentous thalli with strikingly low morphological diversity. Consequently, microscopic identification of these organisms is difficult, and often possible only to higher taxonomic units. We investigated the taxonomic and phylogenetic composition of green microalgae isolated from biofilms growing on the bark of Quercus pubescens and Pinus nigra. The study was based on 122 partial sequences of the plastid-encoded rbcL gene. In total, 29 operational taxonomic units (OTUs), differing in their rbcL sequences, were encountered. Members of the Trebouxiophyceae formed 97.5% of the isolates; Streptophyta made up 2.5%. The most frequently occurring OTUs were in the genera Coccomyxa, Parachloroidium and Stichococcus. Within the Watanabea clade, we have probably discovered an as-yet undescribed generic lineage with chlorelloid morphology. OTUs belonging to the recently described trebouxiophycean genera Kalinella, Leptochlorella and Xylochloris were als...
TL;DR: Freshwater woloszynskioid dinoflagellates were collected independently in Scotland and Portugal and found to belong to a previously unknown species of the genus Borghiella, here described as B. andersenii, proving that such ‘gymnodinioids’ or ‘wolosZynskios’ comprise an often overlooked biological entity in both marine and freshwater biotopes.
Abstract: Freshwater woloszynskioid dinoflagellates were collected independently in Scotland and Portugal and found to belong to a previously unknown species of the genus Borghiella, here described as B. andersenii. The new species differs in morphology and nuclear-encoded LSU rDNA and ITS sequences from B. dodgei and B. tenuissima, the two species presently comprising the genus Borghiella. Unusual features of the new species were observed particularly during asexual reproduction, which took place in the motile stage – as in many other dinoflagellates – or in a so-called division cyst, recalling cell division in the family Tovelliaceae. Such diversity in cell division is rarely reported in dinoflagellates. Morphologically Borghiella andersenii differs from B. tenuissima in being only slightly compressed dorsoventrally whereas the latter species is flat. The slight compression is also visible in lateral view. Borghiella andersenii and B. dodgei are more challenging to discriminate but the apical structure complex is...
TL;DR: An integrative approach, using both morphological and molecular data (COI-5P + rbcL), is undertook, to assess the presence of Laurencia pyramidalis in Lusitanian Macaronesia and the geographical distribution of LaureNCiella marilzae, a species recently described from the Canary Islands.
Abstract: In the present study we undertook an integrative approach, using both morphological and molecular data (COI-5P + rbcL), to assess the presence of Laurencia pyramidalis in Lusitanian Macaronesia. We studied type material of L. pyramidalis from the herbarium of the Naturalis Biodiversity Center, the Netherlands, and designated a lectotype and syntypes. Vegetative and reproductive features of L. pyramidalis were observed and we included a specimen from the type locality in our molecular analyses. We also investigated the geographical distribution of Laurenciella marilzae, a species recently described from the Canary Islands. Barcode sequences (COI-5P and rbcL) were generated for L. pyramidalis from the type locality (Normandy, France), the Azores, Madeira and the Canary Islands, and for L. marilzae from its type locality (Tenerife, Canary Islands), the Azores and Brazil.
TL;DR: A molecular study using 3′ rbcL + 5′ rBCL–S sequences was undertaken to assess the diversity of foliose Bangiales on the west coast of Greenland and rbc l sequences were used to study the Greenland flora in a larger phylogenetic and floristic context.
Abstract: Greenland is a continental island in the northern part of the North Atlantic where the foliose Bangiales flora is poorly known. It is an important area for the study of algal biogeography because of the region’s glacial history, in which Greenland has been alternately exposed to or isolated from the North Pacific via the Bering Strait. A molecular study using 3′ rbcL + 5′ rbcL–S sequences was undertaken to assess the diversity of foliose Bangiales on the west coast of Greenland and rbcL sequences were used to study the Greenland flora in a larger phylogenetic and floristic context. New and historic collections document seven species in four genera from the west coast of Greenland. All species had a close link to North Pacific species, being either conspecific with them or North Atlantic–North Pacific vicariant counterparts.
TL;DR: In this article, a culture of Heterocapsa minima collected in the south-west of Ireland was used to provide important information for this species, including cell size, cell organelle location, thecal plate pattern, body scale fine structure and molecular phylogeny.
Abstract: The dinophycean genus Heterocapsa is of considerable interest as it contains a number of bloom-forming and/or harmful species. Fine structure of organic body scales is regarded as the most important morphological feature for species determination but currently is unknown for the species H. minima described by Pomroy 25 years ago. Availability of a culture of H. minima collected in the south-west of Ireland allowed us to provide important information for this species, including cell size, cell organelle location, thecal plate pattern, body scale fine structure and molecular phylogeny. Light microscopy revealed the presence of one reticulate chloroplast, an elongated centrally located nucleus, and the presence of one pyrenoid surrounded by a starch sheath. Scanning electron microscopy (SEM) of the thecal plate pattern indicated that Pomroy erroneously designated the narrow first cingular plate as a sulcal plate. In addition, SEM revealed as yet unreported details of the apical pore complex and uncommon orna...
TL;DR: It is demonstrated that Nf reduced photosynthesis in the green alga Chlamydomonas reinhardtii more strongly at 15 than at 25ºC, while Fd showed stronger effects at 25 than at 15ºC.
Abstract: Norflurazon (Nf) and fluridone (Fd) are phytoene desaturase inhibitor herbicides that are widely used for the control of grasses and invasive aquatic weeds, respectively. These herbicides enter aquatic environments where they can negatively affect non-target plant species (e.g. algae). Their toxicity towards algae may be modified by abiotic factors such as light intensity, temperature, pH and nutrients. Investigating the effect of low temperature on the toxicity of Nf and Fd is particularly important because both temperature and herbicides affect some of the same physiological process (e.g. carotenoid biosynthesis). Here we demonstrate that Nf reduced photosynthesis in the green alga Chlamydomonas reinhardtii more strongly at 15 than at 25oC, while Fd showed stronger effects at 25 than at 15oC. Neither herbicide significantly inhibited photosynthesis at 8oC. Although the overall pigment content decreased with lower temperature, there was an increase in photo-protective carotenoids relative to chlorophylls...
TL;DR: A new species of Tovellia, T. aveirensis, is described on the basis of light and scanning electron microscopy of motile cells and resting cysts and phylogenetic analysis of partial sequences of the large subunit ribosomal rRNA gene.
Abstract: A new species of Tovellia, T. aveirensis, is described on the basis of light (LM) and scanning electron microscopy (SEM) of motile cells and resting cysts, complemented with transmission electron microscopy (TEM) of flagellate cells and phylogenetic analysis of partial sequences of the large subunit ribosomal rRNA gene. Both vegetative cells and several stages of a life cycle involving sexual reproduction and the production of resting cysts were examined in cultures established from a tank in the University of Aveiro campus. Vegetative cells were round and little compressed dorsoventrally; planozygotes were longer and had a proportionally larger epicone. Chloroplast lobes were shown by TEM to radiate from a central, branched pyrenoid, although this was difficult to ascertain in LM. The amphiesma of flagellate cells had mainly 5 or 6-sided vesicles with thin plates, arranged in 5–7 latitudinal series on the epicone, 3–5 on the hypocone. The cingulum had 2 rows of plates, the posterior row extending into th...
TL;DR: The suitability of culturing in combination with molecular identification of young sporophytes to address several key aspects of kelp ecology related to the existence of a bank of microscopic stages in the field is illustrated.
Abstract: This paper describes a method to study the diversity of young kelp sporophytes that are recruited from the bank of microscopic stages Small samples of rocky substratum (05 cm2) were collected from the low intertidal zone, which was dominated by the kelp Laminaria digitata Samples were cultivated in the laboratory under conditions permitting gametogenesis Sporophyte recruits in the cultures were isolated and identified at the species level using the barcoding mitochondrial marker rpl31–rns Sixty per cent of the collected samples had at least one to a maximum of 30 kelp recruits, belonging to five different species (L digitata, L hyperborea, L ochroleuca, Saccharina latissima and Sacchorhiza polyschides) As the examination of freshly collected rocky samples under a stereo microscope did not reveal any kelp sporophytes, the recruitment in these samples after culture probably occurred from the bank of microscopic forms present on the substratum Despite the dominance of L digitata in the field, the young sporophytes obtained after culturing were mainly S polyschides This study illustrates the suitability of culturing in combination with molecular identification of young sporophytes to address several key aspects of kelp ecology related to the existence of a bank of microscopic stages in the field
TL;DR: A taxonomic assessment of tube-forming species that were originally described on the basis of colony morphology can only proceed using clonal cultures or single-cell analysis, and this study provides the first molecular survey of these taxa.
Abstract: Limited molecular data for marine tube-forming diatoms are available currently and this study provides the first molecular survey of these taxa. To conduct this survey, we used a molecular-assisted alpha taxonomy (MAAT) approach that utilizes DNA barcode data. We used three DNA barcode markers: the 3´ end of the large subunit of RUBISCO (rbcL-3P); the variable D2/D3 region of the nuclear large subunit ribosomal DNA (LSU D2/D3); and the internal transcribed spacer 2 (ITS2) to assign marine tube-forming diatoms from Canada to genetic species groups. The rbcL-3P analysis uncovered 29 genetic groups including representatives of Haslea crucigera, Navicula bottnica, N. brunelii, N. ramosissima, Nitzschia fontifuga, N. tubicola, Parlibellus berkeleya and P. delognei f. elliptica, as well as a complex of 14 closely related groups morphologically consistent with Berkeleya rutilans. We sequenced ITS2 for representatives of the B. rutilans complex; these data were consistent with the rbcL-3P genetic clusters for 86%...
TL;DR: Molecular phylogenies inferred from ribosomal genes failed to confirm any clear relationship with other benthic taxa and affinity with other laterally compressed dinoflagellates has not been demonstrated, hence, the taxonomic affinity of Madanidinium loirii with a defined order and family is unclear at the moment.
Abstract: A new benthic phototrophic dinoflagellate is described from sediments of a tropical marine cove at Martinique Island and its micromorphology is studied by means of light and electron microscopy. The cell contains small golden-brown chloroplasts and the oval nucleus is posterior. It is laterally compressed, almost circular in shape when viewed laterally. It consists of a small epitheca tilted toward the right lateral side and a larger hypotheca. In the left view, the cingulum is more anterior and the epitheca is reduced. The cingulum is displaced and left-handed. This organism is peculiar in having no apical pore and its thecal plate arrangement is 2′ 1a 7′′ 5c 3s 5′′′ 1′′′′. The plates are smooth with small groups of pores scattered on their surface. An area with 60–80 densely arranged pores is found near the centre of the 2′′′ plate, on the left lateral side. Morphologically, these features are different from all other laterally compressed benthic genera. In addition, molecular genetic sequences of SSU a...
TL;DR: The hypothesis that biofilm development could have been subject to multistability is discussed, i.e. the existence of several possible stable biofilm configurations for the same set of environmental parameters might have been sufficient to switch between these different configurations and thus have contributed to overwriting the original effects of temperature and flow velocity.
Abstract: In the present study, biomass development and changes in community composition of phototrophic biofilms grown under different controlled ambient conditions (light, temperature and flow) were examined. Source communities were taken from a wastewater treatment plant and used to inoculate growth surfaces in a semi-continuous-flow microcosm. We recorded biofilm growth curves in cultures over a period of 30 days across 12 experiments. Biovolume of phototrophs and community composition for taxonomic shifts were also obtained using light and electron microscopy. Species richness in the cultured biofilms was greatly reduced with respect to the natural samples, and diversity decreased even further during biofilm development. Diadesmis confervacea, Phormidium spp., Scenedesmus spp. and Synechocystis spp. were identified as key taxa in the microcosm. While a significant positive effect of irradiance on biofilm growth could be identified, impacts of temperature and flow rate on biofilm development and diversity were ...
TL;DR: Overall, the results indicated significant differences in the physiological responses of the five diatom taxa during UV exposure, which suggests species-specific acclimation strategies that may explain the growth insensitivity towards at least short-term UV.
Abstract: Benthic diatoms inhabiting intertidal flats face highly variable environmental conditions, due to changing water levels and exposure during low tide. The present study is the second part of a more extensive study of the adaptive potential of these species in response to varying UV radiations in the Solthorn tidal flat (Lower Saxony, southern North Sea). Five isolates (Achnanthes exigua, Amphora exigua, Cocconeis peltoides, Diploneis littoralis and Navicula digitoradiata), which were found in this area in high cell numbers in summer 2008, were used in semi-continuous cultures to study the physiological effects of UV-radiation (PAR [photosynthetically active radiation], PAR+UV-A, PAR+UV-B, PAR+UV-B+UV-A). For short- and long-term exposures (6 h, 30 days), the composition of intercellular carbohydrates, amino and fatty acids were analysed in exponential-phase cultures grown at a salinity of 30 in a 12 : 12 h light : dark cycle at 20 °C. Although all tested species showed distinct differences in their initial...
TL;DR: It is suggested that colony formation is initiated by aggregation of motile cells following P pulses in the water, and Comparisons are made with Rivularia, a competitor in this nitrate-rich river, in spite of being a N2-fixer.
Abstract: The ecology of Chroothece was studied in the highly calcareous Rio Chicamo, south-east Spain, in order to explain its success there, but rarity elsewhere. The river, which originates mainly from an underground aquifer, has water with high conductivity, sulphate and nitrate but low phosphate concentrations, the latter mainly organic. Chroothece occurs in mats and in lobed colonies reaching 4 cm in the broadest dimension. The colony surface consists of one layer of cells, each of which is attached to a stalk, which dichotomizes when the cell divides; stalks often extend to the colony base. The central region of many mat cells and almost all colony cells has a yellow to orange-brown colour, associated with the numerous lipid droplets densely covering the surface of the pyrenoid and arms of the star-shaped chloroplast. Field material and laboratory isolates indicate that stalk formation occurs under moderate P limitation and both stalks and cell sheath show high phosphatase activities. This also occurred in a...
TL;DR: There are two separated P. boryana lineages, one restricted to the Gulf of Thailand and the other to the Andaman Sea and other areas of the Indo-Pacific, based on persistent currents in the area.
Abstract: The Indo-Pacific Ocean is a biodiversity hotspot for marine organisms. In this area, most of the research has focused on marine animals, such as reef fish, molluscs and other associated coral fauna, but very little has been done on macroalgae. The Thai-Malay Peninsula is an important north–south barrier in this area, which faces two different oceans – the Indian Ocean and the Pacific Ocean. This study aims to investigate genetic distribution patterns of Padina boryana Thivy around the Thai-Malay Peninsula, where it is common. Three DNA marker regions, the mitochondrion-encoded cytochrome c oxidase subunit 3 gene (cox3); the plastid rbcL, and the nuclear internal transcribed spacer 2 (ITS2) were used to evaluate genetic diversity and the relationships within and between populations. Samples were collected from both the Andaman Sea and Gulf of Thailand sides of the peninsula. Parsimony networks and maximum likelihood and Bayesian analyses showed clearly that there are two separated P. boryana lineages, one ...
TL;DR: Detailed information is provided on the characteristics of limnic Ulva habitats and indicate the niches where such populations are likely to occur.
Abstract: Species of Ulva (Ulvaceae, Chlorophyta) are relatively common macroalgae in most coastal areas. In this paper, we examine Ulva in inland aquatic ecosystems to determine relationships between the chemical parameters of the water and the Ulva taxa present. Two groups of samples of freshwater Ulva were selected from: (i) habitats with high salinity levels, and (ii) habitats with fresh or slightly saline waters. We showed that these two groups of Ulva, which occupy distinct habitats, represent two separate taxa. The first group represents Ulva flexuosa subsp. pilifera (Kutzing) M.J. Wynne, which is very common and regularly encountered in fresh waters, but is equally well represented in slightly saline waters. The second is U. flexuosa subsp. paradoxa (C. Agardh) M.J. Wynne, which is less common, preferring mainly salt-wedge saline waters. We did not find both Ulva flexuosa subspecies together at any of the research sites.There were significant morphological differences between the Ulva flexuosa subspecies. U...