Showing papers in "European Journal of Phycology in 2012"
TL;DR: Production of gold nanoparticles by algae is more ecofriendly than purely chemical synthesis, however, the choice of algae is important: Chara zeylanica and Pithophora oedogoniana were found to be unable to produce nanoparticles.
Abstract: The cyanobacteria Phormidium valderianum, P. tenue and Microcoleus chthonoplastes and the green algae Rhizoclonium fontinale, Ulva intestinalis, Chara zeylanica and Pithophora oedogoniana were exposed to hydrogen tetrachloroaurate solution and were screened for their suitability for producing nano‐gold. All three cyanobacteria genera and two of the green algae (Rhizoclonium fontinale and Ulva intestinalis) produced gold nanoparticles intracellularly, confirmed by purple colouration of the thallus within 72 h of treatment at 20°C. Extracted nanoparticle solutions were examined by UV‐vis spectroscopy, transmission electron microscopy (TEM) and X‐ray diffractometry (XRD). XRD confirmed the reduction of Au (III) to Au (0). UV‐vis spectroscopy and TEM studies indicated the production of nanoparticles having different shapes and sizes. Phormidium valderianum synthesized mostly spherical nanoparticles, along with hexagonal and triangular nanoparticles, at basic and neutral pHs (pH 9 and pH 7, respectively). Medi...
145 citations
TL;DR: A new genus and species of subaerophytic cyanobacteria with very thin purple-red trichomes with a photosensitive orange spot at the tip of the trichome containing a rhodopsin-like pigment is proposed, Oculatella subterranea.
Abstract: A new genus and species of subaerophytic cyanobacteria with very thin purple-red trichomes are described. The seven strains included in this genus were isolated from phototrophic biofilms growing on calcareous substrata in ancient hypogea. Trichomes were 1–3 µm thick, with small constrictions at the cross-walls and colourless sheaths. The thylakoid arrangement was parietal. Autapomorphic characters include the purple-red colouration of cells and a photosensitive orange spot at the tip of the trichome containing a rhodopsin-like pigment. Molecular and phylogenetic analyses based on 16 S rRNA gene sequences, resulted in a new 16 S rRNA cluster that indicated a separate position at the generic level. All strains were closely related (99% or higher similarity) and distantly related to other established cyanobacterial taxa (92%). The 16 S–23 S rRNA internal transcribed spacer (ITS) sequence of five of the red strains was almost identical. The ITS secondary folding structure was also unique to these strains and...
89 citations
TL;DR: The high increase in the transcript levels of the cytochrome-dependent carotene β- and ε-hydroxylases in response to high light suggests an important role of these enzymes in regulation of xanthophyll synthesis upon light stress.
Abstract: The carotenoid biosynthesis pathway catalyses the synthesis of essential pigments that are crucial for light harvesting and photoprotection in photosynthetic organisms. It allows the production of ...
67 citations
TL;DR: Investigating the intracellular toxicity mechanisms of the photoactive, potentially anti-cyanobacterial agent hydrogen peroxide in Microcystis aeruginosa confirmed that light is one of the critical factors affecting H2O2 decomposition and thus greatly influences its toxicity.
Abstract: The aim of our study was to investigate the intracellular toxicity mechanisms of the photoactive, potentially anti-cyanobacterial agent hydrogen peroxide (H2O2) in Microcystis aeruginosa, which represents one of the most significant toxin-producing cyanobacterial species in European water bodies. Metabolic activity and cell membrane integrity were evaluated by flow cytometry in cyanobacteria exposed to H2O2 in the dark or light; the relationships between exposure effects and the kinetics of hydrogen peroxide decomposition were studied. In the light (irradiance 140 µmol m−2 s−1), cyanobacteria were exposed to initial H2O2 concentrations of 0.00 (control), 0.75, 2.00, and 4.00 mg l−1 respectively, while in the dark concentrations were ten times higher. Flow cytometry and chlorophyll a fluorescence measurements suggested that hydrogen peroxide exposure elicits an immediate decline of metabolic (esterase) activity, measured as a decrease in fluorescein fluorescence after hydrolysis of fluorescein diacetate (F...
65 citations
TL;DR: All strains studied form a monophyletic lineage within the Chlorophyceae containing species from different habitats and all species have characteristic compensatory base changes in their ITS secondary structures and are supported by ITS-2 DNA barcodes.
Abstract: Traditionally the genus Microglena Ehrenberg has been used to contain species that belong to the Chrysophyceae; however, the type species of Microglena, M. monadina, represents a green alga, which was later transferred to the genus Chlamydomonas. The taxonomic status of the genus has therefore remained unclear. We investigated 15 strains previously assigned to C. monadina and two marine species (C. reginae and C. uva-maris) using an integrative approach. Phylogenetic analyses of SSU and ITS rDNA sequences revealed that all strains form a monophyletic lineage within the Chlorophyceae containing species from different habitats. The strains studied showed similar morphology with respect to cell shape and size, but showed differences in chloroplast and pyrenoid structures. Some representatives of this group have the same type of sexual reproduction (homothallic advanced anisogamy). Three different morphotypes could be recognized. Strains belonging to type I have a cup-shaped chloroplast with a massive basal p...
61 citations
TL;DR: Overall, C. raciborskii was frequently present in the temperate lakes of western Poland, but it was most abundant in eutrophic lakes with high conductivity and high concentrations of TN and TP but low concentrations of and .
Abstract: Cylindrospermopsis raciborskii has recently attracted wide attention owing to its toxigenicity and its capacity for rapid invasion of new geographical regions. We studied the spatial distribution of C. raciborskii in western Poland and the environmental variables related to its occurrence near the border of its current temperate geographical range. We also identified the typical phytoplankton assemblages in which C. raciborskii occurs. Forty-six lakes were sampled once during the summers of 2008 and 2009. C. raciborskii was present in 43% of the samples and its biomass accounted for 0.1–13.9% of the total phytoplankton biomass found in the lakes. A General Linear Model (GLM) analysis and t-tests showed that the lakes in which C. raciborskii occurred were significantly shallower, more turbid and more eutrophic than the lakes from which it was absent. Redundancy Analysis (RDA) and GLM analyses showed that C. raciborskii biomass correlated positively with total nitrogen (TN), total phosphorus (TP) and conduc...
56 citations
TL;DR: Haslea karadagensis is the first example of a new ‘blue’ diatom and produces a novel blue pigment, and significant differences were observed by micro-Raman spectroscopy in the 1000–1700 cm−1 wavenumber range, revealing that the pigments are different molecules.
Abstract: A new species of raphid pennate diatom producing a blue pigment, Haslea karadagensis Davidovich, Gastineau & Mouget, sp. nov., was recently isolated from the Crimean coast of the Black Sea (Ukraine). This organism is very similar to the well-known Haslea ostrearia, the first described ‘blue’ diatom, which produces marennine, the pigment involved in the greening of oysters. The Ukrainian diatom, H. karadagensis, differs slightly from H. ostrearia in the structure of its frustule, and the two organisms are unable to interbreed. Two molecular markers, rbcL and the ITS1–5.8S–ITS2 sequences, showed 2% and >50% differences, respectively, between the two species. UV-visible spectrophotometry and in vivo confocal micro-Raman spectroscopy were used to compare the pigment of H. karadagensis with marennine. Both pigments showed absorption bands in the UV and red regions, but the positions of the maxima differ between the pigments. Significant differences were observed by micro-Raman spectroscopy in the 1000–1700 cm−...
45 citations
TL;DR: A molecular study using rbcL and cox1 sequences was undertaken to assess the diversity of foliose Bangiales species in Iceland and the Faroe Islands, revealing a total of 13 species, which were referred to four of the genera recognized in a recent two-gene global phylogeny.
Abstract: Foliose species of the Bangiales (Porphyra sensu lato) have a long history of study in the N Atlantic, but there are still regions, especially in the northern parts of the N Atlantic that need more attention. A molecular study using rbcL and cox1 sequences was undertaken to assess the diversity of foliose Bangiales species in Iceland and the Faroe Islands. Herbarium collections from the intertidal and subtidal of Iceland (summer and winter) and the Faroe Islands (all seasons) revealed a total of 13 species (11 common to both areas), which were referred to four of the genera recognized in a recent two-gene global phylogeny. Boreophyllum birdiae, Porphyra dioica, P. linearis, P. purpurea, P. umbilicalis, Pyropia ‘leucosticta’ A, Pyropia njordii Mols-Mortensen, J. Brodie & Neefus, sp. nov., Wildemania amplissima and W. miniata were common to both areas, while Pyropia thulaea and Wildemania abyssicola (Kjellman) A. Mols-Mortensen & J. Brodie, comb. nov. (=Porphyra abyssicola Kjellman) were reported from Icela...
42 citations
TL;DR: The statistical analysis confirmed that the composition of the microphytobenthos was related to sediment features and to characteristics of particular seasons, depending on species-specific requirements as well as hydrodynamic conditions (tidal currents).
Abstract: The microphytobenthos colonizing the intertidal flats forms an important component of the Wadden Sea. Ten sampling points along a 1-km transect were studied in a fringe area of the Solthorn tidal flat, southern North Sea, in order to determine seasonal differences in the microphytobenthos. An accompanying paper deals with the major component of the flora, the diatoms; here we, focus on the minor taxonomic groups. From May 2008 to May 2009 surface sediments were collected during low tide. Variation of environmental factors as well as microphytobenthic density (abundance and chlorophyll a) were monitored. The area investigated was a mixed-sediment mudflat, with a gradient from coarse to fine. Highest biomass was obtained in summer 2008 with 215.9 ± 12.6 mg chlorophyll a m–2. In late autumn the chlorophyll a concentration decreased continuously at all investigated stations. Lowest values were detected in December 2008. Species abundances varied considerably both along the transect and seasonally, depending o...
42 citations
TL;DR: Morphology and ITS2 phylogeny indicated that the level of diversity within the genus is higher than previously estimated (e.g. among P. delicatissima and P. galaxiae).
Abstract: A total of 92 cultured Pseudo-nitzschia strains, established between March 2007 and April 2010 from Greek coastal waters, were identified by using morphological and molecular (ITS2 region) characters. Twelve species were identified, among which P. brasiliana, P. subpacifica and P. hasleana were detected for the first time near Greek and East Mediterranean coasts. One P. delicatissima-like morphotype and another strain that closely resembled P. dolorosa were also found. Morphology and ITS2 phylogeny indicated that the level of diversity within the genus is higher than previously estimated (e.g. among P. delicatissima-like diatoms). Additionally, the ITS2 phylogeny revealed genetic variation within species, indicative of geographical differentiation (in P. brasiliana, P. fraudulenta, P. arenysensis, P. delicatissima and P. galaxiae). The majority of the cultured strains were also tested for domoic acid (DA) production. Strains of only three species, P. pseudodelicatissima, P. galaxiae and P. pungens var. pu...
40 citations
TL;DR: The results of statistical analysis indicate that the distribution patterns of some epipelic and epipsammic diatom taxa are related to nutrient availability, particularly of silicate and ammonium.
Abstract: The benthic diatoms composition of the surface sediments were sampled at two-weekly intervals from May 2008 to May 2009 at ten stations along a transect across the intertidal zone of the Solthorn tidal flat (southern North Sea, Germany). Inorganic macronutrients (nitrate, nitrite, silicic acid and reactive dissolved phosphate) in the overlying water showed a distinct seasonal cycle, with high winter and low summer values. The benthic diatom assemblages exhibited both seasonal and spatial distribution patterns, showing distinctive differences in species composition among summer, autumn, winter and spring communities. Independent of season, all structures were characterized by the dominance of small epipelic species such as Navicula phyllepta, N. digitoradiata, N. gregaria and N. salinicola, with seasonal successions of secondary species, including several larger benthic (e.g. Pleurosigma angulatum, Gyrosigma peisonis) and pelagic species (Plagiogramma and Thalassionema). In addition, the communities contai...
TL;DR: The distribution of G. vermiculophylla in Europe suggests that it thrives well in hyposaline environments and that it may be more fit than some native algae under such conditions, but this may not explain its present success relative to many naturally occurring algal species.
Abstract: Non-native, invasive species are often characterized by being tolerant to environmental stressors, leaving them more fit relative to native species The red alga Gracilaria vermiculophylla originates from the NW Pacific but has recently spread along the coastlines of Western Europe, where it has become abundant in many shallow, soft-bottom estuaries Salinity is important for the local and regional distribution of algae The distribution of G vermiculophylla in Europe suggests that it thrives well in hyposaline environments and that it may be more fit than some native algae under such conditions Little, however, is known about the ecophysiology of G vermiculophylla and it is therefore difficult to predict its spread and future distribution Laboratory experiments with G vermiculophylla showed that steady-state salinity above 15 psu was optimal for growth and that the growth rate was reduced at salinities below 15 psu Variable salinity reduced the growth rate and larger oscillations were more stressfu
TL;DR: The results imply that, while diatom species composition reflects well the environmental differences between regions, future bioassessments would benefit from regional stratification because relationships with environmental variables may be masked by trans-regional differences in species pools caused by the large-scale processes.
Abstract: Diatoms are widely used in stream quality assessment due to their response to the local environment. Diatoms are also influenced by many large-scale processes and so the diatom communities of boreal streams incorporate a strong spatial component at a regional level. What is not properly known yet is whether the variation in diatom communities between regions is larger than the variation in measured environmental variables. We studied the roles of environment and space in accounting for variability in stream diatom communities across four regions in Finland. According to canonical correspondence analysis, geographical coordinates, nutrient concentrations (total N and P), and water conductivity were the most important factors affecting variation in diatom community composition. Of physical factors, depth and current velocity were also significant. According to Mantel tests, both environmental and geographical distances were related to dissimilarity in diatom community composition. Analysis of Similarities i...
TL;DR: St sterol concentrations of phytoplankton are strongly affected by temperature and nutrient supply, and interactive effects point out the importance of taking into account more than just one environmental factor when assessing the effects of environmentally induced changes.
Abstract: The understanding of environmentally induced changes in the biochemical composition of phytoplankton species is of great importance in both physiological studies and ecological food web research. In extensive laboratory experiments we tested the influence of two different temperatures (10°C and 25°C) and a phosphorus supply gradient on the sterol concentrations of the three freshwater phytoplankton species Scenedesmus quadricauda, Cryptomonas ovata and Cyclotella meneghiniana. The diatom C. meneghiniana was additionally exposed to a silicate gradient. In two separate experiments we analysed (1) possible interactive effects of temperature and phosphorus supply and (2) the effect of four phosphorus levels and three silicate levels on algal sterol concentrations. We observed that sterol concentrations were higher at 25°C than at 10°C in S. quadricauda and C. meneghiniana, but were not affected by temperature in C. ovata. Interactive effects of temperature and phosphorus supply on sterol concentrations were f...
TL;DR: Laurencia obtusa from the Northern Atlantic is confirmed to represent a distinct species, which displays high genetic divergence with respect to western and eastern Atlantic samples.
Abstract: Morphological and molecular studies have been performed on Laurencia dendroidea derived from Brazil and the Canary Islands. This species possesses all of the characters that are typical of the genus Laurencia, including the production of the first pericentral cell underneath the basal cell of the trichoblast; the production of tetrasporangia from particular pericentral cells without the formation of additional fertile pericentral cells; spermatangial branches that are produced from one of two laterals on the suprabasal cell of the trichoblasts; and a procarp-bearing segment that possesses five pericentral cells. The phylogenetic position of L. dendroidea was inferred by analysing the chloroplast-encoded rbcL gene sequences of 51 taxa. Phylogenetic analyses revealed that the taxa previously identified and cited in Brazil as Laurencia filiformis, L. majuscula and L. obtusa and in the Canary Islands as L. majuscula all represent the same taxonomic entity and examination of type material allowed us to identif...
TL;DR: Metabolic fingerprinting is applied in a taxonomic study of a cryptic diatom species to reinforce differences found for morphology, phylogenetic markers and growth rates, and point at different adaptive characteristics in organisms living under different temperature regimes.
Abstract: Morphology and molecular phylogeny constitute the structural elements of diatom taxonomy. These approaches do not, however, give information on the functioning of taxa. Additional methods to serve ...
TL;DR: The acclimation to high light of Phaeodactylum tricornutum cultures grown outdoors both in an open pond and in tubular photobioreactors (PBRs) was studied by means of chlorophyll fluorescence, pigment analysis and growth, which correlated well with changes in the photochemical parameters.
Abstract: The acclimation to high light of Phaeodactylum tricornutum cultures grown outdoors both in an open pond and in tubular photobioreactors (PBRs) was studied by means of chlorophyll fluorescence, pigment analysis and growth. Cultures grown in PBRs (5-cm tube diameter) at two biomass concentrations (0.3 and 0.6 g l−1) were compared with a culture grown in a 10-cm deep open pond (0.3 g l−1). Therefore, the performance of the cultures was compared on the basis of both the same biomass concentration and areal density. Cultures grown at 0.3 g l−1 in PBRs experienced the highest light stress, which resulted in dramatic changes in both chlorophyll fluorescence and photosynthesis parameters, and in low areal productivity. In this culture, the Fv/Fm ratio was 0.5 in the morning and dropped to about 0.1 within 1 h of exposure to bright sunlight. Similar behaviour was observed with the measurements of rETR, and the initial slope (αETR) of the photosynthesis curve, while the saturation irradiance parameter (Ik) increase...
TL;DR: Cyanobacteria are normal constituents of the benthic microflora in tropical regions, but their abundance, diversity and species composition changes with environmental conditions and so do the rates of N2 fixation on the lagoon floors.
Abstract: Cyanobacteria have been found to be important for primary production and nitrogen supply on coral reefs. Here, the distribution of cyanobacteria that dominate microbial mats (identified by using microscopic and molecular tools), their abundance, and specific contributions and timing of N2 fixation, were studied in two coral reef systems of the western Indian Ocean: Mayotte (Comoros) and Tulear (Toliara, Madagascar). The results were compared with previously published data from the reefs of La Reunion Island (Mascarenes). Variations in nutrient levels, temperature and light penetration (Secchi) were also measured and compared. The reefs in Mayotte are situated in oligotrophic ocean waters and support coral reefs in good condition. The reef of Tulear was overgrown by algae. The shallow lagoon and reef in La Reunion showed signs of eutrophication and coral degradation. All three reefs maintained a diverse population of benthic cyanobacterial mats. A total of 13 different cyanobacterial morphotypes were encou...
TL;DR: Significant differences in osmolyte compositions were found in the three diatom species during exposure to different salinities, suggesting specific intracellular acclimation processes that provide possible explanations of the species’ insensitivity towards environmental short-time salinity variations.
Abstract: Diatoms inhabiting intertidal flats are subject to strongly changing salinities due to exposure to rain and desiccation at low tide. In order to determine the physiological responses of marine benthic diatoms to salinity changes, cultures of Navicula phyllepta, Achnanthes delicatula subsp. hauckiana and Nitzschia constricta, isolated from the Solthorn tidal flat (lower Saxony, southern North Sea), were used to study the effect on growth rates of different salinities (0.5, 10, 20, 30, 40, 50). During short (1, 3, 10, 60 min) and long exposures (30 days), the composition of free amino acids and the accumulation of polyols, saccharides, quaternary ammonium compounds and β-dimethylsulphoniopropionate (DMSP) were determined. The growth rates of N. phyllepta were not affected by salinity in the tested range, synthesizing and accumulating proline as the only response to salinity increases in the growth medium. The growth responses of A. delicatula subsp. hauckiana were significantly weaker at the lowest and high...
TL;DR: A comprehensive cDNA library from RNA sampled under various light andTemperature regimes is constructed, as a basis for future studies about the mechanisms and pathways involved in acclimation to light and temperature stress in Saccharina latissima.
Abstract: Macroalgae of the order Laminariales (kelps) are important marine coastal primary producers with prime significance for ecosystem function. Important factors influencing their distribution include light and temperature but the molecular basis of kelp responses to these factors is poorly understood. We therefore constructed a comprehensive cDNA library from RNA sampled under various light and temperature regimes, as a basis for future studies about the mechanisms and pathways involved in acclimation to light and temperature stress in Saccharina latissima. A total of 400 503 ESTs was assembled into 28 803 contigs. We were able to assign putative functions or orthology relationships to more than 10 000 contigs by BLASTx, Interpro protein-motif annotation, or Gene Ontology (GO). The most frequent Interpro protein domains found in the cDNA library were the protein kinase-like domain, serine/threonine-protein kinase-like domain, and NAD(P)-binding and thioredoxin-like fold domain. Enzyme code (EC) annotation yi...
TL;DR: A new sprawling species, Codium pernambucensis, is described based on morphology and molecular analyses of Brazilian Codium species grouped with morphologically similar taxa from other geographic localities, and are present in all three main clades.
Abstract: The genus Codium comprises c. 125 species widely distributed in marine coastal environments throughout the world. Due to morphological plasticity, the taxonomic delimitation of Codium species can be difficult. Sequences of the first exon of the large subunit of RUBISCO (rbcL) have been used in the molecular delimitation of species and for phylogenetic purposes. In the present study, we complement previous morphological work on Brazilian Codium species with molecular systematics. Based on the partial rbcL sequences, seven species are recognized along the Brazilian coast: C. decorticatum, C. intertextum, C. isthmocladum, C. profundum, C. spongiosum, C. taylorii and the new species Codium pernambucensis. Ten unique sequences were obtained among the samples examined, which we used in combination with previously published sequences to infer molecular phylogenies using various methods. The resulting trees showed three principal monophyletic groupings: Clade A with species having a prostrate habit, not branched,...
TL;DR: It is concluded that below 20°C photoinhibition is avoided by greater photoprotection in the invasive species C. raciborskii compared to the native species A. gracile.
Abstract: The freshwater cyanobacterium Cylindrospermopsis raciborskii spreads from tropical to temperate regions worldwide. This entails acclimation to varied light and temperature conditions. We studied the thermal and light acclimation of the photosynthetic machinery of C. raciborskii by monitoring alteration of the chlorophyll a and carotenoid content in German strains of C. raciborskii, in African and Australian strains of C. raciborskii, and in German strains of Aphanizomenon gracile, a native cyanobacterium belonging to the same order (Nostocales). Our results showed that temperate and tropical C. raciborskii strains did not differ in pigment acclimation to light and temperature. In contrast, the ratio of photoprotective carotenoids (namely the carotenoid glycoside 4-hydroxymyxol glycoside [aphanizophyll]) to chlorophyll a increased significantly more in C. raciborskii in comparison with A. gracile (1) with decreasing temperatures from 20 to 10°C and a moderate light intensity of 80 µmol photons m−2 s−1 and ...
TL;DR: This work resolved species level taxonomy and phylogeographical distribution patterns in the freshwater rhodophyte Sirodotia through phylogenetic inferences based on rbcL and cox2–3 sequence data and supported the synonymy of S. tenuissima and S. suecica.
Abstract: Species level taxonomy and phylogeographical distribution patterns in the freshwater rhodophyte Sirodotia are resolved through phylogenetic inferences based on rbcL and cox2–3 sequence data. Previous studies focused on the taxonomy of specific Sirodotia species or the distributions across a limited geographical region. Our molecular phylogenies included samples attributable to five recognized Sirodotia species and include collections from Australia, Brazil, Costa Rica, Canada, Finland, Mexico, New Zealand, South Africa and the United States. Both rbcL and cox2–3 phylogenies inferred S. suecica, S. tenuissima and S. goebelii as a monophyletic group with little sequence divergence. This result supports the synonymy of S. tenuissima and S. goebelii with S. suecica (the species name with priority). Within this clade, samples collected from Australia and New Zealand formed a monophyletic group with no other discernible phylogeographical patterns within S. suecica. This result seems to be somewhat unusual in th...
TL;DR: Two picoplanktonic diatoms, one isolated from an upwelling ecosystem in the Pacific Ocean and another from oceanic waters in the Indian Ocean, were used to test hypotheses on the functional relation between ecological niche adaptation and photosynthetic regulation capacity and efficiency.
Abstract: Reaching up to 50% of the total biomass in oligotrophic waters and armed with a set of ecological and biological properties related to their small size, picophytoplankton (<3.0 µm) are a good model to address ecophysiological questions regarding phytoplankton biodiversity. Two picoplanktonic diatoms, one isolated from an upwelling ecosystem in the Pacific Ocean (Minutocellus sp., strain RCC967), and another from oceanic waters in the Indian Ocean (Minutocellus sp., strain RCC703) were used to test hypotheses on the functional relation between ecological niche adaptation and photosynthetic regulation capacity and efficiency. Cultures were subjected to five sine light climates, each one set to peak at a different photon flux density, respectively 10, 50, 100, 250 and 500 µmol photons m−2 s−1. Growth rate, photosynthesis, non-photochemical fluorescence quenching, pigment composition, and particulate organic carbon and nitrogen content were followed daily for 5 days. Growth rate and physiological response cur...
TL;DR: The technique described here provides a simple and rapid means of estimating primary productivity in marine systems and is similar to published values of productivity of Antarctic species derived from oxygen- and carbon-based techniques.
Abstract: Photosynthetic activity of marine macroalgae in the Windmill Islands, East Antarctica, was measured in situ using submersible modulated fluorometers. An empirical relation incorporating terms for respiration and non-linear electron transport was derived from simultaneous in vivo measurements of effective quantum yield ( ) and oxygen evolution. This relation was used with in situ measurements of and photosynthetic photon flux density acquired over 24-h periods to estimate oxygen evolution rates of algae over the course of the measurement period. Productivity ranged from −8 to 19 µmol O2 g−1 FW h−1 (FW = fresh weight), with daily carbon gain ranging from −1.5 to 3.6 mg C g−1 FW d−1 for midnight ice-covered algae and midday ice-free algae, respectively. These values were similar to published values of productivity of Antarctic species derived from oxygen- and carbon-based techniques. The technique described here provides a simple and rapid means of estimating primary productivity in marine systems.
TL;DR: Salinity-induced developmental plasticity and difference in the ‘reaction norm’ of clonal cultures of Cyclotella meneghiniana, isolated from different locations, and their F1 offspring and genetic distances between strains and the phylogenetic position of each strain were investigated.
Abstract: We investigated salinity-induced developmental plasticity and difference in the ‘reaction norm’ of clonal cultures (genotype–environment [G × E] interaction) of Cyclotella meneghiniana, isolated from different locations, and their F1 offspring. Genetic distances between strains and the phylogenetic position of each strain were investigated by partial 28S rDNA sequencing. In addition, we investigated morphological differences between cells obtained from different sites along a tidal river, from the lower reaches to the river mouth. In laboratory culture, all strains exhibited a greater number of central fultoportulae (CFP = central strutted processes) in saline medium (salinity, 17 psu) than in freshwater medium; the number of striae on the valve and the diameter of the central area increased in all but three strains. A significant G × E interaction was detected in the number of CFP, the number of striae, the diameter of the central area and the valve diameter. Pair-wise comparison showed significant G × E...
TL;DR: In this article, molecular and morphological data for specimens from the coral triangle and peripheral Indo-Pacific localities (East African coast, Hawaii) were used to understand species delimitation for selected branched Halymenia spp.
Abstract: Several species in the red algal genus Halymenia from the Indo-Pacific have been described with branched thalli, toothed margins, spinose proliferations on the blade, and a firm gelatinous texture. Previous works have synonymized many of these morphologically similar species with H. durvillei. Our increased taxon sampling and molecular data indicate that the taxonomy of the Indo-Pacific Halymenia species is in need of revision, and that several aspects of taxonomies proposed by previous authors now seem unlikely. Thus, the aim of the present work was to analyse species delimitation in branched Halymenia species. Molecular and morphological data for specimens from the coral triangle and peripheral Indo-Pacific localities (East African coast, Hawaii) were used to understand species delimitation for selected branched Halymenia spp. Phylogenetic analyses based on 29 rbcL gene sequences grouped the specimens in four well-supported clusters at the species level with high p-distances (2.7–5.3%). After the morpho...
TL;DR: The experiments showed that the scattering signatures of unaggregated diatom species are conservative and that LISST instruments are useful tools to investigate the factors affecting diatom aggregation and disaggregation, with potential applications both in the laboratory and field.
Abstract: Laser in situ scattering and transmissometry (LISST) instruments are used to measure particle size distributions (PSDs) and volume concentrations in water. For populations of regularly shaped non-spherical particles, such as phytoplankton, the PSD produces a ‘scattering signature’ that corresponds to the shape of the particles. The objectives of this research were to describe the scattering signatures of six diatom species and to determine whether LISST instruments can be used as a tool to measure the aggregation of diatoms into larger particles. The scattering signatures of Chaetoceros muelleri var. subsalsum, Coscinodiscus wailesii, Thalassiosira weissflogii, Phaeodactylum tricornutum, Skeletonema costatum and S. marinoi were measured. The scattering signatures of individual species were consistent over time in batch culture and there were clear differences between species in terms of peak location, peak width, and relative peak height in the PSD. LISST was used to non-destructively follow the formation...
TL;DR: During autumn 2007, an unusual increase in an algal species belonging to the order Prymnesiales was observed throughout the Baltic Sea Proper during routine national monitoring, and electron microscopical examination of the blooming species showed two types of flat scales that resembled those of the alternate stage of Prymnesium polylepis.
Abstract: During autumn 2007, an unusual increase in an algal species belonging to the order Prymnesiales was observed throughout the Baltic Sea Proper during routine national monitoring. Electron microscopical examination of the blooming species showed two types of flat scales – small and large – that resembled those of the alternate stage of Prymnesium polylepis. No spine-bearing scales were found. The 18S rDNA sequence data (n = 20, c. 1500 bp) verified the species identification as P. polylepis. There was up to 0.5% (7 bp) variability in the P. polylepis partial 18 S rDNA sequences from the Baltic Sea. These environmental sequences differed by 0–0.35% (0–4 bp) from cultured P. polylepis (isolate UIO036), and by 1.0–3.7% from other available Prymnesium sequences. The number of cells assumed to be P. polylepis began to increase in October 2007 coincidently with significantly calm and dry weather, and at their maximum the cells accounted for over 80% of the total phytoplankton biovolume in December–January. During...
TL;DR: From the higher DIC affinity, more efficient photosynthetic capacity and increased percentages in competition experiments under low DIC concentration, it can be concluded that the bloom-forming M. aeruginosa possesses a competitive advantage in DIC-limited conditions.
Abstract: The availability of dissolved inorganic carbon (DIC) may have a considerable impact on species competition in phytoplankton communities. The growth, photosynthetic characteristics and competition of three strains, the toxic Microcystis aeruginosa FACHB 912, nontoxic M. aeruginosa FACHB 469 and Chlamydomonas microsphaera FACHB 52, were investigated under two different DIC concentrations (0.365 and 7.658 mmol l−1 KHCO3). In monoculture, DIC concentration did not affect the specific growth rates of any of the three strains. However, when grown in mixed culture with C. microsphaera, both toxic and nontoxic Microcystis strains showed increased percentages under low DIC concentration but decreased percentages under high DIC concentration. After 12 days’ mixed culture, the percentage of M. aeruginosa FACHB 912 or FACHB 469 decreased by 9−22% in high DIC medium, but increased by 6–11% in low DIC medium. Low DIC concentration decreased the cell size, cellular chlorophyll fluorescence and photosynthetic capacity of...