Diatom Algae Research Articles

Late Cretaceous seasonal ocean variability from the Arctic

The modern Arctic Ocean is regarded as a barometer of global change and amplifier of global warming and therefore records of past Arctic change are critical for palaeoclimate reconstruction. Little is known of the state of the Arctic Ocean in the greenhouse period of the Late Cretaceous epoch (65-99 million years ago), yet records from such times may yield important clues to Arctic Ocean behaviour in near-future warmer climates. Here we present a seasonally resolved Cretaceous sedimentary record from the Alpha ridge of the Arctic Ocean. This palaeo-sediment trap provides new insight into the workings of the Cretaceous marine biological carbon pump. Seasonal primary production was dominated by diatom algae but was not related to upwelling as was previously hypothesized. Rather, production occurred within a stratified water column, involving specially adapted species in blooms resembling those of the modern North Pacific subtropical gyre, or those indicated for the Mediterranean sapropels. With increased CO(2) levels and warming currently driving increased stratification in the global ocean, this style of production that is adapted to stratification may become more widespread. Our evidence for seasonal diatom production and flux testify to an ice-free summer, but thin accumulations of terrigenous sediment within the diatom ooze are consistent with the presence of intermittent sea ice in the winter, supporting a wide body of evidence for low temperatures in the Late Cretaceous Arctic Ocean, rather than recent suggestions of a 15 degrees C mean annual temperature at this time.

The seasonal and interannual dynamics of centric diatoms in the Kuibyshev Reservoir

Samples of centric diatom algae from the plankton of the Kuibyshev Reservoir collected in years with different hydro-meteorological conditions (1989 and 1990) have been studied using light and scanning electron microscopy technique. Twenty-nine species, varieties, and forms of Centrophyceae, including two species new for the algoflora of the Volga River plankton, have been discovered. The main body of the dominant species is formed by algae with a high frequency of occurrence. The seasonal dynamics of abundance is characterized by spring peaks formed mainly by small-celled algae and less regular late fall maximums formed by large-celled forms. During these periods the abundance of Centrophyceae determines the level of phytoplankton development in general. Under stable species richness of algae and seasonal dynamics of their abundance, the average number of Centrophyceae during the hot and low-water year of 1989 reached 3.6 million cells/l; during the cold and high-water year of 1990, there were twice as few: 1.9 million cells/l.

Characterization of Two Putative Protein Translocation Components in the Apicoplast ofPlasmodium falciparum

Protein trafficking to the stroma of the apicoplast of Plasmodium falciparum requires translocation across several membranes. To further elucidate the mechanisms responsible, we investigated two proteins: P. falciparum Tic22 (PfTic22), a putative component of the translocon of the inner chloroplast membrane; and PfsDer1-1, one of two homologues of the P. falciparum symbiont-derived Der1 (sDer1) protein, a putative component of an endoplasmic reticulum-associated degradation (ERAD) complex in the periplastid membrane. We constructed parasites expressing hemagglutinin (HA)-tagged PfTic22 and PfsDer1-1 under the control of their endogenous promoters using the 3' replacement strategy. We show that both PfTic22-HA and PfsDer1-1-HA are expressed predominantly during the trophozoite stage of the asexual replication cycle, which corresponds to the most dynamic stages of apicoplast activity. Although both proteins localize to the periphery of the apicoplast, PfTic22-HA is a membrane-associated protein while PfsDer1-1-HA is an integral membrane protein. Phylogenetic analysis indicates that PfsDer1-1 is one of two Der1 paralogues predicted to localize to the apicoplast in P. falciparum and that it has orthologues in diatom algae, supporting the chromalveolate hypothesis. These observations are consistent with putative roles for PfTic22 and PfsDer1-1 in protein translocation into the apicoplast of P. falciparum.

Ultrafast fluorescence study on the location and mechanism of non-photochemical quenching in diatoms

The diatom algae, responsible for at least a quarter of the global photosynthetic carbon assimilation in the oceans, are capable of switching on rapid and efficient photoprotection, which helps them cope with the large fluctuations of light intensity in the moving waters. The enhanced dissipation of excess excitation energy becomes visible as non-photochemical quenching (NPQ) of chlorophyll a fluorescence. Intact cells of the diatoms Cyclotella meneghiniana and Phaeodactylum tricornutum, which show different NPQ induction kinetics under high light illumination, were investigated by picosecond time-resolved fluorescence under dark and NPQ-inducing high light conditions. The fluorescence kinetics revealed that there are two independent sites responsible for NPQ. The first quenching site is located in an FCP antenna system that is functionally detached from both photosystems, while the second quenching site is located in the PSII-attached antenna. Notwithstanding their different npq induction and reversal kinetics, both diatoms showed identical NPQ via both mechanisms in the steady-state. Their fluorescence decays in the dark-adapted states were different, however. A detailed quenching model is proposed for NPQ in diatoms.

The species composition and distribution of diatom algae in sphagnum bogs in European Russia: The Polistovo-Lovatskii land tract

The species composition of diatom algae in the Polistovo-Lovatskii sphagnum tract (Rdeiskoye bog, Novgorod oblast) \are studied. The systematic and ecological-geographical analyses of the flora are performed. A total of 256 species and intraspecific taxa differing in ecological specificities and frequencies of occurrence in samples are revealed. A considerable number of centric diatoms is found. It is shown that primary and secondary diatom communities are formed in large sphagnum tracts. The horizontal heterogeneity of diatom communities in sphagnum bog is revealed. The species diversities of diatom algae in different bogs are compared.

Sorption of silicic acid from non-saturated aqueous solution by a complex of zinc ions with poly(vinylamine)

Silicifying organisms (diatom algae, sponges, etc.) build multifarious silica and composite nano-structures which attracts rapt attention of specialists in nanotechnology. These organisms can capture monomeric silicic acid from diluted solutions (<1 mM) and molecular mechanism of this process is still unknown. Some hypotheses include mediatorial role of zinc ions coordinated with a special protein transporter. We have studied several basic hydrogels and their complexes with double charged metal ions in sorption of silicic acid from non-saturated solutions. Cross-linked poly(vinylamine) coordinated with Zn 2+ was able to capture silicic acid from 0.1 to 1.7 mM solutions. The other ions (Cu 2+, Fe 2+, Ni 2+, Co 2+, Cd 2+ and Mn 2+) and less basic poly(1-vinylimiazole) were not active in the sorption. A mechanism included oligomerization of silicic acid and formation of triple complex poly(vinylamine)-Zn 2+-oligosiloxane was proposed. FTIR, NMR and EDS data confirm this conclusion. The found capture of silicic acid from diluted solutions with polyamine–zinc complex shows possibility in principle of the zinc-mediated transmembrane transport of Si(OH) 4 in silicifying organisms. On the other hand, the ability of zinc ions immobilized on the polyamine support to capture oligosilicates could be used in directed assembly of nanocomposite structures by the “bottom-up” approaches.

Trophic relationships in the community of a bivalve mollusk and a boring polychaete

The community of the Japanese scallop Mizuhopecten yessoensis with its dominant endobiont polychaete Polydora brevipalpa, which bores into the scallop’s shell, was studied. It was established that the bulk of the scallop’s food ration consists of diatom algae and, to a lesser extent, flagellates and small invertebrates. The polychaete species considered mainly assimilates diatom algae and, to a significant degree, bacteria. Thus, the elements of the community enter competitive food relations. In the process of feeding, the scallop excretes detritus with its pseudofeces and this way increases the concentration of food available for polychaetes. In the course of its motion and filtration, the scallop enhances the water flow around the polychaete, which also favors the feeding of the latter. Meanwhile, negative relations between the degree of the population of the scallop’s shell by polychaetes and the volume of its internal cavity were recognized; this indicates a decrease in the potential for water filtering and, correspondingly, for food procuring by the host mollusk. With the increase in the polychaete-related bioerosion of the shell, the linear sizes and weight parameters of the scallop fall together with the rate of its growth.

Photosynthesis and respiration of a deep-water periphyton community (Macclesfield Bank, South China Sea)

The production parameters of the deep-water periphyton were investigated on the Macclesfield Bank (South China Sea) at depths down to 240 m. At 70–90 m depths the substrate is composed of the remains of dead corals and fragments of porous calcareous material overgrown with red coralline and articulated thalline algae Halimeda sp. At 220–240 m depths the substrate consists of rhodolites, which are individual unattached nodules encrusted mainly with red calcareous coralline algae Lithophyllum sp., Porolithon sp. and red lamellar alga Hypoglossum sp. At all depths the substrate is pierced with green filiform algae Ostreobium sp. and covered with benthic diatom algae. The zooperiphyton in the studied area is comprised of bryozoans, sponges, foraminifers and drilling mollusks. Respiration (R) and the gross (Pg) and net (Pn) primary production of the deepwater periphyton community were determined using the oxygen technique (polarographic electrode) at values of photosynthetically active radiation (PAR) close to natural levels. At 70–90 m depths the Pg of the photoperiphyton was 23.3 mg O2/(m2 h), and the Pn of the community had negative values due to respiration of phytoand mainly zooperiphyton and bacteria. At 220–240 m depths, where less than 0.001% of the surface PAR penetrates, the Pg of the phytoperiphyton decreased to 9.6 mg O2/(m2 h), and the R of the community was 25.9 mg O2/(m2 h). A high efficiency of light energy utilization by the phytoperiphyton was found. The apparent quantum yield (Fa) for algae collected at 70–90 m depths was close to the maximum level of 0.097. The values of Fn that we obtained for 220–240 m depths and calculated from identical data [27], were much higher than theoretical values, which cannot be explained based on modern views on the mechanisms of photosynthesis. Possible sources of errors are discussed. It is proposed that we observed additional evolution of oxygen as the result of H2O2 degradation.

Light absorption and scattering by cell suspensions of some cyanobacteria and microalgae

Absorption spectra of cyanobacteria (Anacystis nidulans, Anabaena variabilis, and Chlorogloeopsis fritschii), red (Cyanidium caldarum and Porphyridium cruentum), green (Dunaliella maritima and Dunaliella salina) and diatom (Thalassiosira weisflogii) alga cell suspensions are presented; the spectra were obtained by using an approach developed earlier to compensate for scattering [1, 2]. In all species, the shapes of the absorption spectra were independent of the cell concentration. For Th. weisflogii and D. maritima, the analysis of selective and nonselective scattering was carried out. The effect of mechanical cell disruption on optical properties (absorption, scattering, and “package” effect) on D. maritima was studied. The character and dynamics of optical changes in D. salina under the influence of sodium chloride were followed.

Long-term changes in phytoplankton composition in seven Canadian Shield lakes in response to multiple anthropogenic stressors

We examined long-term changes in phytoplankton composition from 1981 to 2003 in seven intensively studied lakes on the southern Canadian Shield in Ontario, Canada. Significant (P &lt; 0.05), temporally coherent increases in the relative biovolume of colonial chrysophytes were observed in six of the seven lakes, with coincident declines in the relative biovolume of diatom algae. Variance partitioning analyses identified water chemistry variables, and the co-variation of water chemistry with physicoclimatic variables, as most important in structuring phytoplankton assemblages through time in the study lakes (variance explained: chemical variables (14%–47%, mean = 28.7%); chemistry and physicoclimatic variables (21%–30%, mean = 25.5%)). With the exception of Harp Lake, which was invaded by Bythotrephes in the early 1990s, grazing variables did not explain a significant portion of the phytoplankton variance. We hypothesize that the long-term changes in phytoplankton species composition is attributable to multiple anthropogenic stressors acting at a regional scale. Our results, coupled with paleoecological studies, indicate that increases in the relative importance of colonial chrysophytes are coincident with water chemistry changes associated with industrial activity since the mid-1900s and physical changes linked to climate indices such as the North Atlantic Oscillation.

Centric diatom algae of the Selenga River and its delta branches

Different stages of the study of taxonomical composition of centric diatoms in the Selenga River are considered. A revision of the species composition and a general systematic list are made. New for the Selenga River diatom species are discovered. The role of small-sized centric diatoms in different years and vegetation periods is assessed. A comparison of the composition and the level of development of centric diatoms in 1958–1959 and 2002–2005 is made.

NEW TAXONS OF BENTHIC DIATOM ALGAE OF THE TILIGUL ESTUARY (THE NORTH-WESTERN PART OF THE BLACK SEA COAST)

181 species and taxons of the diatom algae were revealed in benthos of the Tiligul Estuary. 74 of them are represented for the reservoir for the first time and 25 for the first time for the estuaries of the north-western part of the Black Sea. Cocconeis scutellum var. tiligulicus Kovtun var. nov. and Fallacia gusliakovi Kovtun sp. nov. are described as new species for science. The original micrographs are presented.

Changes in the hydrochemical composition and diatomic flora of bottom sediments in the zone of influence of metal mining production (Kola Peninsula)

Paleoecological studies of small water bodies were carried out in a model subarctic lake-river system. The degree of transformations of aquatic ecosystems under a set of anthropogenic factors is shown to vary depending on the load and individual features of water bodies. Data on the state of aquatic ecosystems before the industrial development of the region are collected. The species composition of diatom algae and their ecological characteristics are examined.

Algal communities associated with aquatic macrophytes in some artificial ponds in Nyando District, Kenya

This study describes the algal communities of six ponds colonised by aquatic macrophytes in Nyanza Province, Kenya. Plankton samples were collected from the water column and epiphytic samples from macrophytes such as Azolla, Pistia, Nymphaea, Ipomoea and Ludwigia. Pond pH, temperature, conductivity, concentration and dissolved oxygen saturation were also measured. The algal flora of the ponds comprised 139 species and varieties from 58 genera. Diatoms and green algae, mostly desmids, were the dominant groups. About 50 of the algal taxa were indicators of low mineral content of the water. Four distinct diatom communities were identified, using Canonical Correspondence Analysis. The constant dominant taxa were Achnanthes sp., Gomphonema gracile and Pinnularia gibba. The analysis showed that all samples from the same pond were grouped together, irrespective of the aquatic plants sampled.

Characterization of aerobic bacterial and fungal microbiota on surfaces of historic Scottish monuments

Twenty samples were taken from the inner or outer surfaces of stone monuments of six historic Scottish buildings and ruins. Biofilms developing on mineral substrates were analysed by in situ scanning electron microscopy and cultivation. Various methods were used to characterize the isolates including automated ribotyping, RAPD and sequencing of the 16S rRNA gene for bacteria, and stereomicroscopy and sequencing of the Internal Transcribed Spacers (ITS) for fungi. Most samples contained microbes between 10 5 and 10 7 cfu g −1 substrate. Actinobacteria belonging to the genus Streptomyces (17 samples/5 monuments) or Arthrobacter (12/3) and Pseudomonas (9/3) were frequently detected. Most streptomycetes were in terms of their 16S rRNA gene sequence most closely related to S. microflavus (10/3) or to the undescribed species S. “vulgaris” (8/3). Indoor and outdoor biofilms exhibited significant differences in their microbiota, as shown by both microscopy and isolation studies. Pigmented coccoid Arthrobacter species were typical for the outdoor samples, whereas Pseudomonas species were common in the indoor samples. Based on the low phylogenetic relationship to a known species (type strain), potential novel pigmented bacterial species belonging to the genera Arthrobacter, Brevundimonas, Cryseobacterium, Deinococcus and Dyadobacter were detected from the outdoor samples and to Pseudomonas from the indoor samples. Hyaline fungal species of Acremonium (10/4) mainly occurred in indoor samples, whereas pigmented species of Cladosporium (8/3), Penicillium (6/3) and Phialophora (6/2) were found outdoors. Using in situ microscopy diatom algae were also detected.

Structure of plankton phytocoenoses in the shelf waters of the northeastern Black Sea during the Emiliania huxleyi bloom in 2002–2005

It is shown that, in 2002–2005, the mass development of the coccolithofore Emiliania huxleyi on the Gelendzhik shelf occurred annually and in May–June its abundance reached 1.5 × 106 cells/l. In 2004–2005, the bloom of E. huxleyi was accompanied by a mass development of the diatom alga Chaetoceros subtilis var. abnormis f. simplex (0.6–0.9 × 106 cells/l); for the first time, it was registered as a dominating form of the Black Sea phytoplankton. Small flagellates and picoplankton algae played a noticeable role in the phytoplankton throughout the entire period of the studies. Meanwhile, in the early summer period, the bulk of the biomass consisted of coccolithophores (50–60%), while, in the late summer period, diatomaceous algae dominated (50–70%). Among the ecological factors that favor the coccolithophore development one may note the microstratification of the upper mixed layer at a high illumination level and high temperature in the surface waters (18–21°C). The terrigenous runoff during the rainy period had a negative effect on the E. huxleyi development, while storms dispersed the population over the upper mixed layer. The wind-induced near-shore upwelling stimulated the development of diatoms.

Distribution of Pelagic Invertebrates Near a Thermal bar in Lake Baikal

In Lake Baikal, frontal zones are a factor forming the pelagic structure, including area limits of pelagic communities. The spacial distribution of Baikal micro-organisms and diatom algae is known to be influenced by the vertical circulation of Lake Baikal deep waters during the spring thermal bar. In June 2001, we studied the distribution of plankton invertebrates and ways in which it depends on physico-chemical and biological parameters of water in the vicinity of spring thermal bars. Samples were taken through June 11–13th along three transects, across the middle basin of Lake Baikal and the Selenga shallow waters, namely at the Boldakovo River, Cape Sukhinskiy and the Kukuy branches of the Selenga River. As a consequence of the lake possibly being warmed later than usual, and compare with a previous study in 1993, the upper layers with temperatures close to 4 °C, were located near the shore where water depth was 14–100 m, from north to south. The littoral waters, warmed above 4 °C and reaching 12.7 °C near Cape Sukhinskiy, are known to differ from the open lake in hydrochemical indexes, raised number of bacterioplankton and the structure of algae coenoses (in particular, the presence of algae which indicate the spread of the Selenga River waters). An unusual vertical distribution of autotrophic picoplankton in terms of raised concentrations at the bottom, 60 m deep, occurred at the Cape Sukhinskiy transect within a thermal bar zone. This indicated the descent of upper waters rich in picoplankton. The zooplankton structure in the littoral also differed from that in more open waters where temperatures were below 4 °C, mainly by its richer diversity increased by littoral inhabitants. The pelagic amphipod Macrohectopus branickii preferred cold waters less than 4 °C. Crustaceans and rotifers were separated into different groups according to spacial distribution.

Are the Lake Baikal diatoms endemic?

An electron-microscopy study of Aulacoseira baicalensis, A. islandica (A. skvortzowii), Cyclotella baicalensis, C. minuta, and Stephanodiscus meyerii in phytoplankton samples from some mountain lakes of Zabaikalye (an area north and east of Lake Baikal) shows that these algae possess morphological similarities with the algae inhabiting Lake Baikal, including some elements of their ultra-structure. We hypothesise that they were more widespread in the past and persist today in mountain lakes along the Baikal rift zone owing to certain features of their biology. We conclude that these baikalian diatom algae, previously regarded as endemic, should be re-assigned to relict status.

The role of endemic diatom algae in the phytoplankton of Lake Baikal

An estimate of the role of endemic diatom algae of Lake Baikal, their contribution to numerical abundance and to biomass, was obtained on the basis of long-term monitoring in the pelagic zone, and in shallow water bays and near the mouths of rivers. Endemic diatoms are distributed over a major part of the lake, except for shallow-water bays. During a major part of the year, they dominate in biomass and in numerical abundance, making a major contribution to the rate of accumulation of modern sediments.

A Plant Locus Essential for Phylloquinone (Vitamin K1) Biosynthesis Originated from a Fusion of Four Eubacterial Genes

Phylloquinone is a compound present in all photosynthetic plants serving as cofactor for Photosystem I-mediated electron transport. Newly identified seedling-lethal Arabidopsis thaliana mutants impaired in the biosynthesis of phylloquinone possess reduced Photosystem I activity. The affected gene, called PHYLLO, consists of a fusion of four previously individual eubacterial genes, menF, menD, menC, and menH, required for the biosynthesis of phylloquinone in photosynthetic cyanobacteria and the respiratory menaquinone in eubacteria. The fact that homologous men genes reside as polycistronic units in eubacterial chromosomes and in plastomes of red algae strongly suggests that PHYLLO derived from a plastid operon during endosymbiosis. The principle architecture of the fused PHYLLO locus is conserved in the nuclear genomes of plants, green algae, and the diatom alga Thalassiosira pseudonana. The latter arose from secondary endosymbiosis of a red algae and a eukaryotic host indicating selective driving forces for maintenance and/or independent generation of the composite gene cluster within the nuclear genomes. Besides, individual menF genes, encoding active isochorismate synthases (ICS), have been established followed by splitting of the essential 3' region of the menF module of PHYLLO only in genomes of higher plants. This resulted in inactivation of the ICS activity encoded by PHYLLO and enabled a metabolic branch from the phylloquinone biosynthetic route to independently regulate the synthesis of salicylic acid required for plant defense. Therefore, gene fusion, duplication, and fission events adapted a eubacterial multienzymatic system to the metabolic requirements of plants.