Distribution Of Diatoms Research Articles

Observations on diatoms inhabiting natural and artificial substrates in Kongsfjorden, Svalbard, the Arctic

The most dramatic effects of global climate change are predicted for the Arctic, and there is a raising concern about the lack of baseline information on microalgal biodiversity. The present study was motivated by the general lack of information on species distribution of Arctic benthic diatoms and particularly studies providing photographs to facilitate morphological species identification. Diatoms were studied in samples collected from Ny Alesund, Spitsbergen, Svalbard, during summer 2006 and spring 2008. Two types of samples were examined: diatoms scraped from ceramic tiles, immersed at 0.5 m depth (2006), and diatoms extracted from surface sediment, collected at 0.5 to 3 m depth (2008). A total number of 75 taxa belonging to 45 genera were encountered. Sixty-eight species were found in the sediment samples and 48 on the ceramic tiles, of which 41 species were found on both substrata. Common species of the tile assemblages were Fragilariopsis spp., Licmophora spp., Odontella aurita, Synedropsis hyperborea and Trachyneis aspera, while Thalassiosira spp., Diploneis spp. and Navicula spp. were common in the sediment samples. Twenty-five percent of the observed diatom species belonged to freshwater taxa brought to the fjord from surrounding meltwater and river discharges.

The species composition, morphology, and seasonal distribution of diatoms of the genus Attheya West, 1860 from the Sea of Japan

Six species that belong to the diatom genus Attheya were found in the Russian waters of the Sea of Japan. A. cf. flexuosa is a new record for the seas of Russia. A. decora is recorded for the first time for the Sea of Japan. The peculiarities of the morphology of A. decora and A. cf. flexuosa are described and illustrated. The study of the seasonal distribution, abundance, and ecology of Attheya species in the northwestern Sea of Japan showed that A. longicornis and A. ussurensis were the most numerous and widespread species, reaching maximum densities (up to 1.5 × 106 and 1.8 × 104 cells/liter, respectively) in the spring, summer, and fall. A. cf. flexuosa and A. septentrionalis were rare and were found in low numbers in the winter and early spring. Based on the ultrastructure of the girdle bands, the form and number of chloroplasts, the presence/absence of rimoportula on the valve, and habitat features, we distinguished two groups of species of the genus Attheya from the Sea of Japan. The first group includes psammophytes A. decora, A. arenicola, and A. ussurensis; the second one comprises A. longicornis and A. cf. flexuosa epiphytic on other diatoms, as well as A. septentrionalis, which is found in the under-ice plankton and is able to attach to the underside of ice.

Distribution and diversity of diatom assemblages in surficial sediments of shallow lakes in Wapusk National Park (Manitoba, Canada) region of the Hudson Bay Lowlands.

The hydrology of shallow lakes (and ponds) located in the western Hudson Bay Lowlands (HBL) is sensitive to climate warming and associated permafrost thaw. However, their biological characteristics are poorly known, which hampers effective aquatic ecosystem monitoring. Located in northern Manitoba along the southwestern coast of Hudson Bay, Wapusk National Park (WNP) encompasses numerous shallow lakes representative of the subarctic zone. We analyzed the distribution and diversity of diatom (microscopic algae; class Bacillariophyceae) assemblages in surficial sediments of 33 lakes located in three different ecozones spanning a vegetation gradient, from NE to SW: the Coastal Fen (CF), the Interior Peat Plateau (IPP), and the Boreal Spruce Forest (BSF). We found significant differences (P < 0.05) in diatom community composition between CF and IPP lakes, and CF and BSF lakes, but not between IPP and BSF lakes. These results are consistent with water chemistry measurements, which indicated distinct limnological conditions for CF lakes. Diatom communities in CF lakes were generally dominated by alkaliphilous taxa typical of waters with medium to high conductivity, such as Nitzschia denticula. In contrast, several IPP and BSF lakes were dominated by acidophilous and circumneutral diatom taxa with preference for low conductivity (e.g., Tabellaria flocculosa, Eunotia mucophila, E. necompacta var. vixcompacta). This exploratory survey provides a first detailed inventory of the diatom assemblages in the WNP region needed for monitoring programs to detect changes in shallow lake ecosystems and ecozonal shifts in response to climate variations.

Spatial patterns of modern diatom distribution in the Eilandvlei Catchment, Wilderness, South Africa

Spatial patterns of modern diatom distribution in the Eilandvlei Catchment, Wilderness, South Africa

Diatom distribution as an environmental indicator in surface sediments of the West Philippine Basin

The distribution of diatoms from surface sediments of the West Philippine Basin was analyzed, with 68 species and varieties of diatoms from 26 genera identified. Diatom abundance varied spatially, with the absolute abundance of diatoms ranging from 0 to 3.4×104 frustules/g. The seven tropical pelagic diatoms were Alveus marinus, Azpeitia africana, Azpeitia nodulifera, Hemidiscus cuneiformis, Hemidiscus cuneiformis var. ventricosus, Roperia tesselata and Rhizosolenia bergonii. The relative abundance of these species was greater than 20%, and their distribution pattern in the sediments was overlaid by the flow of the Kuroshio Current. Ethmodiscus rex was present at 159 stations, formed the most abundant and dominant species in the diatomaceous ooze, and thus referred to as Ethmodiscus ooze. Ethmodiscus rex was also a major contributor to primary production in the region. A principal component analysis was employed to explain the relationship between samples and variations in diatom species from the WPB. Four diatom assemblages were distinguished, representing different oceanographic conditions; their spatial distributions were closely related with the North Equatorial Current and Kuroshio Current patterns in the region. These diatom assemblages can therefore be useful in deciphering late Quaternary palaeoceanographic reconstructions of the West Philippine Basin.

Vertical distribution of diatoms in the sediment of Al-Huwaiza Marsh, Southern Iraq and their use as indicators of environmental changes

The Mesopotamian marshlands are one of the most internationally important wetlands in the Middle East as it constitutes a nursing ground for many species of birds migrating from North Europe as well as for its rich biodiversity. These marshlands have undergone significant environmental changes during the last three decades owing to decreasing freshwater discharge which has led to water quality deterioration and a changing hydrological regime. This has had a considerable effect on the fauna and flora of the marshes, diminishing their ecological value and significance. The work presented here is the first attempt to investigate the marshes environmental condition during the past two centuries using paleolimnology, specifically diatoms as bioindicators in a sediment core. 80 species of diatom belonging to 35 genera were identified. The taxa encountered in the core are a mixture of fresh and brackish water forms. These are epiphytic and benthic taxa, no planktonic species were found. The fossil diatom community shows that the marshes have been exposed to different periods of salinization as well as eutrophication. The dominance of pollution tolerant species in the core indicates poor water quality for the past 160 years. Paleolimnology is important to understand past environmental conditions and forms a milestone for successful future restoration process. Further work is required to extend the time scale to identify natural ecological states and thresholds to guide international aid restoration projects.

Effect of hydrological variability on diatom distribution in Poyang Lake, China

Poyang Lake is the largest freshwater lake in China, and it has a seasonal flooding cycle that significantly changes the water level every year. The aim of this paper was to explain how these hydrological changes influence diatom populations in Poyang Lake. The yearly hydrological cycle can be divided into 4 phases: low water-level phase, increasing water-level phase, high water-level phase and decreasing water-level phase. Variations in the abundance of planktonic diatoms were studied using quarterly monitoring data collected from January 2009 to October 2013. Generally, diatoms were dominant in Poyang Lake and accounted for more than 50% of the total phytoplankton biomass except in July 2009 (26%) and January 2012 (35%). Aulacoseira granulata and Surirella robusta were the predominant species in all four phases, and they accounted for 25.02% to 56.89% and 5.07% to 14.78% of the total phytoplankton biomass, respectively. A redundancy analysis (RDA) showed that changes in physico-chemical parameter were related to the water level, and changes in diatom biomass were related to nitrite levels and pH. These results indicate that changes in environmental parameters related to both seasonal variations and water-level fluctuations caused variations in diatom biomass and community composition in Poyang Lake. Furthermore, extreme hydrological events can have different influences on the diatom community composition in the main channel and lentic regions. This research provides data on the diatom variations in Poyang Lake and will be useful for establishing biological indicators of environmental change and protecting Poyang Lake in the future.

Monitoring the North Atlantic using ocean colour data

The Remote Sensing Unit (RSU) at the Bedford Institute of Oceanography (BIO) has been monitoring the North Atlantic using ocean colour products for decades. Optical sensors used include CZCS, POLDER, SeaWiFS, MODIS/Aqua and MERIS. The monitoring area is defined by the Atlantic Zone Monitoring Program (AZMP) but certain products extend into Arctic waters, and all-Canadian waters which include the Pacific coast. RSU provides Level 3 images for various products in several formats and a range of temporal and spatial resolutions. Basic statistics for pre-defined areas of interest are compiled for each product. Climatologies and anomaly maps are also routinely produced, and custom products are delivered by request. RSU is involved in the generation of Level 4 products, such as characterizing the phenology of spring and fall phytoplankton blooms, computing primary production, using ocean colour to aid in EBSA (Ecologically and Biologically Significant Area) definition and developing habitat suitability maps. Upcoming operational products include maps of diatom distribution, biogeochemical province boundaries, and products from sensors such as VIIRS (Visible Infrared Imaging Radiometer Suite), OLCI (Ocean Land Colour Instrument), and PACE (Pre-Aerosol, Clouds and ocean Ecosystem) hyperspectral microsatellite mission.

Insights into global diatom distribution and diversity in the world’s ocean

Diatoms (Bacillariophyta) constitute one of the most diverse and ecologically important groups of phytoplankton. They are considered to be particularly important in nutrient-rich coastal ecosystems and at high latitudes, but considerably less so in the oligotrophic open ocean. The Tara Oceans circumnavigation collected samples from a wide range of oceanic regions using a standardized sampling procedure. Here, a total of ∼12 million diatom V9-18S ribosomal DNA (rDNA) ribotypes, derived from 293 size-fractionated plankton communities collected at 46 sampling sites across the global ocean euphotic zone, have been analyzed to explore diatom global diversity and community composition. We provide a new estimate of diversity of marine planktonic diatoms at 4,748 operational taxonomic units (OTUs). Based on the total assigned ribotypes, Chaetoceros was the most abundant and diverse genus, followed by Fragilariopsis, Thalassiosira, and Corethron We found only a few cosmopolitan ribotypes displaying an even distribution across stations and high abundance, many of which could not be assigned with confidence to any known genus. Three distinct communities from South Pacific, Mediterranean, and Southern Ocean waters were identified that share a substantial percentage of ribotypes within them. Sudden drops in diversity were observed at Cape Agulhas, which separates the Indian and Atlantic Oceans, and across the Drake Passage between the Atlantic and Southern Oceans, indicating the importance of these ocean circulation choke points in constraining diatom distribution and diversity. We also observed high diatom diversity in the open ocean, suggesting that diatoms may be more relevant in these oceanic systems than generally considered.

Spatial Distribution of Diatoms and Nutrients in a Mangrove Swamp of Eastern Obolo, Niger Delta

Spatial Distribution of Diatoms and Nutrients in a Mangrove Swamp of Eastern Obolo, Niger Delta

Diatoms from a peat bog on the Pester plateau (southwestern Serbia): New records for diatom flora of Serbia

The distribution of diatoms was studied in three types of diatom communities (epiphytes, benthos and plankton) of a peat bog on the Pester plateau. The observed diatom flora inhabited all investigated communities, comprising in total 250 taxa in 53 genera. Among them, 45 taxa were new records for the Serbian diatom flora. Identified taxa belonged to different groups of algae, however alkaliphile diatoms were dominant. New ecological data for Encyonopsis minuta, Pinnularia isostauron and P. marchica are presented here. All the diatoms were documented by light micrographs, and brief notes on their morphology, distribution and ecology are provided.

Distribution of benthic centric diatom Pleurosira laevis (Compère, 1982) in different substrate type and physical and chemical variables

Abstract: Aim This contribution reports the first regional occurrence of Pleurosira laevis in the Masuleh River, Iran and additionally describes the pattern of occurrence along the Masuleh River and among four substrate types. The aim of this study was to assess the effects of substrate type and physical and chemical variables on distribution of centric diatom P. laevis. Methods At each station, triplicate samples were collected from 4 substrata. Epilithic (assemblages on rock), epidendric (assemblages on wood), epipsammic (assemblages on sand), and epipelic (assemblages on mud) diatom and water quality sampling was done four times at 5 stations. Physical and chemical variables including total nitrate, total phosphate, silicate, Fe2+, EC, and pH were also determined. Samples preserved in 2% for formalin solution and transferred to the laboratory, boiled with acid (HNO3: H2SO4; 2:1), centrifuged, identified, and counted. Cluster analysis was performed to indicate the main differences and similarities in diatom abundance amongst substrates sampled and amongst sampling stations. Results The highest (12.54 ± 1.54) and lowest (0.74 ± 0.10) abundance was obtained from wooden and muddy substrates at stations S5 and S4, respectively. The highest abundance was observed in the wooden substrate among all of sampling stations where showed significant differences (P &lt; 0.05) with the other substrates. The hierarchical clustering based on relative abundance of P. laevis distinguished two clusters amongst the four substrate types. Rougher and more stable substrates (wood, sand, and stone) clearly separated from smooth and unstable substrates (mud). Based on relative abundance of P. laevis on rougher substrates, epidendric and epipsammic species had the highest similarity. Results of Pearson correlation showed that relative abundance of P. laevis had a significant correlation with EC, TN, TP, and Fe2+ concentrations (P &lt; 0.05) whilst no significant correlation was observed with pH, temperature, and SiO2 concentration (P &gt; 0.05). Conclusion We conclude that wood substrata can be substituted for one another during field surveys. Results from this study demonstrate that the type and roughness of the substrate both influence the attachment of P. laevis and its subsequent growth conditions.

DISTRIBUCIÓN Y ABUNDANCIA DE DIATOMEAS DEL GÉNERO PSEUDO-NITZSCHIA EN CONDICIÓN DE EL NIÑO 2007 SOBRE LA CUENCA PACÍFICA COLOMBIANA

The spatial distribution and abundance of diatoms belonging to the genus Pseudo-nitzschia in the Colombian Pacific Basin (CPB) during PACÍFICO XLIV- ERFEN XLII oceanographic survey is described, whereas its relation to temperature and salinity was tested. Samplings of phytoplankton (Niskin bottles 5 L) at two depths (surface and 50 m deep) were carried out in 25 stations. The highest abundances of Pseudo-nitzschia were observed at surface, especially clustered in the intermediate CPB zone. This spatial pattern agreed with low temperature and high salinity values. Consistent with previous data, there were significant differences in the abundance of Pseudo-nitzschia between the two depths sampled (Mann-Whitney test, p = 0.001). A direct relationship between salinity and the genus abundance was set (r = 0.50; p = 0.01), indicating the affinity of these algae to environments with high salinities, whereas an inverse trend was showed with the temperature (r = -0.42; p = 0.043). Although the correlation values are not high, the spatial distribution of biotic and abiotic variables, suggest the influence of salinity and temperature on the abundance and distribution of Pseudo-nitzschia.

Distribution of Epilithic Diatoms in Estuaries of the Korean Peninsula in Relation to Environmental Variables

This study explores the relationships between environmental factors and the distribution of epilithic diatoms in 161 estuaries of three coastal areas on the Korean peninsula. We investigated epilithic diatoms, water quality, and land use in the vicinities of the estuaries during the months of May 2012, 2013 and 2014, because Korea is relatively free from the influences of rainfall at that time of year. We recorded 327 diatom taxa from the study sites, and the assemblage was dominated by members of the Naviculaceae. Bacillariaceae accounted for the largest proportion of diatoms, and Nitzschia inconspicua (18%) and N. frustulum (9.6%) were the most dominant species. A cluster analysis based on epilithic diatom abundance suggested that the epilithic diatom communities of Korean estuaries can be classified into four large groups (G) according to geography, as follows: Ia—the East Sea watershed, Ib—the eastern watershed of the South Sea, IIa—the West Sea watershed, and IIb—the western watershed of the South Sea. The former two groups, Ia and Ib, showed higher proportions of forest land cover and use, higher species occurrence, lower salinity, lower turbidity, and lower concentrations of nutrients than the latter two groups, while the latter groups, IIa and IIb, had higher proportions of agricultural land cover and use, higher electrical conductivity, higher turbidity, higher concentrations of nutrients, and lower species occurrence. The environmental factors underlying the distribution of epilithic diatoms, representative of each region, are as follows: dissolved oxygen and forest land cover and use for Reimeria sinuate and Rhoicosphenia abbreviate of the East Sea (ES), salinity and turbidity for Tabularia fasciculate of the West Sea (WS), and biochemical oxygen demand (BOD) and nutrients for Cyclotella meneghiniana of the WS. On the other hand, the most influential environmental factors affecting the occurrence of indicator species showing the highest indicator values (&gt;60%) of each group were electrical conductivity for Navicula saprophila and Reimeria sinuate of Ia, and turbidity for Encyonema minutum of IIa. Collectively, the distribution of epilithic diatom communities inhabiting Korean estuaries are determined by geographical factors and water quality, which are in turn influenced by land cover and use, and which differ from east to west.

Historical colonization patterns of Dolichospermum lemmermannii (Cyanobacteria) in a deep lake south of the Alps

Since the beginning of the 1990s, Lake Garda showed the appearance of extended surface water blooms of &lt;em&gt;Dolichospermum lemmermannii&lt;/em&gt; (Nostocales, Cyanobacteria). Between the 1990s and the 2000s, the blooms appeared also in the other large lakes south of the Alps (Iseo, Como and Maggiore). Despite the sudden appearance of the blooms, the correct identification of the establishment time of the populations of &lt;em&gt;Dolichospermum&lt;/em&gt; in the southern subalpine lake district remained unclear. In this work, the establishment of the populations of &lt;em&gt;D. lemmermannii&lt;/em&gt; in Lake Garda has been evaluated by the direct counting of sub-fossil akinetes extracted from sediment cores, and by estimating the abundance of filaments germinated from sub-fossil viable akinetes. The two techniques provided comparable results, allowing locating the beginning of the establishment of &lt;em&gt;Dolichospermum&lt;/em&gt; around the middle of the 1960s. Four strains of &lt;em&gt;Dolichospermum&lt;/em&gt; germinated from akinetes isolated from the core sediments between around the 1989 and 2012 did not show any mutation or recombination signal in the rpob gene sequences, suggesting a strong founder effect. The establishment of &lt;em&gt;Dolichospermum&lt;/em&gt; coincided with the beginning of the rapid increase of total phosphorus as inferred from the distribution of sub-fossil diatoms in the sediment core. These results supported the hypothesis of a strong link between the shift of Lake Garda from ultraoligotrophy/oligotrophy to oligo-mesotrophy and the development of &lt;em&gt;Dolichospermum&lt;/em&gt;. This colonisation pattern was possibly reinforced by the increase in the water temperatures in the subalpine lake district during the last 3 decades. In warmer lakes, gas-vacuolated Nostocales are favoured by high replication rates and, in particular, by their ability to control vertical movements in stratified water columns. This allows these species to exploit the gradients of light and nutrients, giving them a competitive advantage compared to other species. From a management point of view, the control and decrease of &lt;em&gt;Dolichospermum&lt;/em&gt; should be obtained through the reduction and control of nutrient loads to the lake.

Climate is an important driver for stream diatom distributions

AbstractAimThe species distributions of macroorganisms are widely studied, yet microbial distributions at species level remain poorly resolved. We explored the relative contributions of climatic and local environmental factors in explaining the distribution patterns of unicellular diatoms.LocationA geographical gradient of c. 1200 km in Finland (60°–70° N).MethodsWe modelled the distributions of 157 diatom taxa sampled in 227 stream sites using climatic and local environmental predictors with four different modelling techniques: generalized linear models, generalized additive models, boosted regression trees and Random Forest. We used models with three separate sets of predictors: environment only, climate only and the full set of predictors. The model performances were evaluated using the area under the curve of a receiver operating characteristic plot and the true skill statistic values by a four‐fold cross‐validation approach.ResultsWe found that the predictive performance of the full models was highest, indicating the importance of both the local environment and large‐scale climatic factors in diatom distribution patterns. However, climate‐only models outcompeted the environment‐only models in predicting diatom distributions. The explanatory variables had varying importance across species and growing degree days and precipitation had the highest relative importance in the full models. We also found that the predictability of the distributions varied greatly among species, but the differences among families were typically small.Main conclusionsOur results suggest that at a broad geographical scale climate‐related factors are important determinants of diatom distributions and may be stronger drivers than local variables. The inclusion of both climatic and local environmental factors in species distribution modelling facilitates the understanding of the joint effects of these drivers on microorganisms in future conditions. From an applied perspective, our study demonstrated that species distribution models serve as an important tool in explaining and predicting microbial distributions.

Distribution and Species Prediction of Epilithic Diatom in the Geum River Basin, South Korea.

Distribution and Species Prediction of Epilithic Diatom in the Geum River Basin, South Korea.

English

English

Census of seafloor sediments in the world’s ocean

Knowing the patterns of distribution of sediments in the global ocean is critical for understanding biogeochemical cycles and how deep-sea deposits respond to environmental change at the sea surface. We present the first digital map of seafloor lithologies based on descriptions of nearly 14,500 samples from original cruise reports, interpolated using a support vector machine algorithm. We show that sediment distribution is more complex, with significant deviations from earlier hand-drawn maps, and that major lithologies occur in drastically different proportions globally. By coupling our digital map to oceanographic data sets, we find that the global occurrence of biogenic oozes is strongly linked to specific ranges in seasurface parameters. In particular, by using recent computations of diatom distributions from pigment-calibrated chlorophyll-a satellite data, we show that, contrary to a widely held view, diatom oozes are not a reliable proxy for surface productivity. Their global accumulation is instead strongly dependent on low surface temperature (0.9–5.7 °C) and salinity (33.8–34.0 PSS, Practical Salinity Scale 1978) and high concentrations of nutrients. Under these conditions, diatom oozes will accumulate on the seafloor regardless of surface productivity as long as there is limited competition from biogenous and detrital components, and diatom frustules are not significantly dissolved prior to preservation. Quantifying the link between the seafloor and the sea surface through the use of large digital data sets will ultimately lead to more robust reconstructions and predictions of climate change and its impact on the ocean environment.

Distribution of diatom, macrophyte and benthic macroinvertebrate communities related to spatial and environmental characteristics: the example of a cut-off meander of the River Allier (France)

Distribution of diatom, macrophyte and benthic macroinvertebrate communities related to spatial and environmental characteristics: the example of a cut-off meander of the River Allier (France)