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  • 1
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The phylogenetic composition of bacterioplankton communities in the water column of four shallow eutrophic lakes was analyzed by partially sequencing cloned 16S rRNA genes and by PCR-DGGE analysis. The four lakes differed in nutrient load and food web structure: two were in a clearwater state and had dense stands of submerged macrophytes, while two others were in a turbid state characterized by the occurrence of phytoplankton blooms. One turbid and one clearwater lake had very high nutrient levels (total phosphorus 〉 100 μg/l), while the other lakes were less nutrient rich (total phosphorus 〈 100μg/l). Cluster analysis, multidimensional scaling and ANOSIM (analysis of similarity) were used to investigate differences among the bacterial community composition in the four lakes.Our results show that each lake has its own distinct bacterioplankton community. The samples of lake Blankaart differed substantially from those of the other lakes; this pattern was consistent throughout the year of study. The bacterioplankton community composition in lake Blankaart seems to be less diverse and less stable than in the other three lakes. Clone library results reveal that Actinobacteria strongly dominated the bacterial community in lake Blankaart. The relative abundance of Betaproteobacteria was low, whereas this group was dominant in the other three lakes. Turbid lakes had a higher representation of Cyanobacteria, while clearwater lakes were characterized by more representatives of the Bacteroidetes. Correlating our DGGE data with environmental parameters, using the BIOENV procedure, suggests that differences are partly related to the equilibrium state of the lake.
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  • 2
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Lakes and ponds in the Larsemann Hills and Bølingen Islands (East-Antarctica) were characterised by cyanobacteria-dominated, benthic microbial mats. A 56-lake dataset representing the limnological diversity among the more than 150 lakes and ponds in the region was developed to identify and quantify the abiotic conditions associated with cyanobacterial and diatom communities.2. Limnological diversity in the lakes of the Larsemann Hills and Bølingen Islands was associated primarily with conductivity and conductivity-related variables (concentrations of major ions and alkalinity), and variation in lake morphometry (depth, catchment and lake area). Low concentrations of pigments, phosphate, nitrogen, DOC and TOC in the water column of most lakes suggest extremely low water column productivity and hence high water clarity, and may thus contribute to the ecological success of benthic microbial mats in this region.3. Benthic communities consisted of prostrate and sometimes finely laminated mats, flake mats, epilithic and interstitial microbial mats. Mat physiognomy and carotenoid/chlorophyll ratios were strongly related to lake depth, but not to conductivity.4. Morphological-taxonomic analyses revealed the presence of 26 diatom morphospecies and 33 cyanobacterial morphotypes. Mats of shallow lakes (interstitial and flake mats) and those of deeper lakes (prostrate mats) were characterised by different dominant cyanobacterial morphotypes. No relationship was found between the distribution of these morphotypes and conductivity. In contrast, variation in diatom species composition was strongly related to both lake depth and conductivity. Shallow ponds were mainly characterised by aerial diatoms (e.g. Diadesmis cf. perpusilla and Hantzschia spp.). In deep lakes, communities were dominated by Psammothidium abundans and Stauroforma inermis. Lakes with conductivities higher than ±1.5 mS cm−1 became susceptible to freezing out of salts and hence pronounced conductivity fluctuations. In these lakes P. abundans and S. inermis were replaced by Amphora veneta. Stomatocysts were important only in shallow freshwater lakes.5. Ice cover influenced microbial mat structure and composition both directly by physical disturbance in shallow lakes and by influencing light availability in deeper lakes, as well as indirectly by generating conductivity increases and promoting the development of seasonal anoxia.6. The relationships between diatom species composition and conductivity, and diatom species composition and depth, were statistically significant. Transfer functions based on these data can therefore be used in paleolimnological reconstruction to infer changes in the precipitation–evaporation balance in continental Antarctic lakes.
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  • 3
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The Schelde estuary, its side basins and their tributaries were sampled in August 1995 and April 1996 for phytoplankton abundance, biomass, diversity and species composition. In order to clarify the underlying causes of differences in phytoplankton communities, the results were related to some important abiotic variables.2. Although species richness and diversity did not differ significantly between the riverine and the freshwater tidal stations, multivariate ordination techniques based on species abundances differentiate between these two ecosystems. While in the rivers phytoplankton standing stocks were as high in summer as in spring, standing stocks in the freshwater tidal estuary were significantly higher in the August samples.3. It is postulated that due to the resuspension of suspended solids by estuarine currents, light is limiting phytoplankton development in the freshwater tidal reaches in spring. At that stage, phytoplankton populations have already developed in the rivers. In summer, zooplankton prevent any further increase of riverine phytoplankton populations. In the freshwater tidal estuary, however, increased light levels, a higher residence time compared to rivers and the absence of zooplankton due to low oxygen concentrations permit phytoplankton populations to bloom.
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  • 4
    ISSN: 1573-0417
    Keywords: diatom assemblages ; altitudinal gradient ; Papua New Guinea ; calibration ; palaeotemperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Indirect and direct gradient ordination techniques were used to study the relationship between present-day benthic and periphytic diatom assemblages and environmental factors along an altitudinal gradient in Papua New Guinea. Both within the screened initial data-set and a narrowly-defined subset of soft-water lakes, shifts in diatom assemblages are clearly related to altitudinal differences. This relation is used to construct transfer functions for inferring altitude (and hence average water temperature) from the diatom records. Calibration by canonical correspondence analysis (CCA) and simple weighted averaging calibration proved to be superior to models using WA with tolerance downweighting and to a simple WA model based on a selection of 52 indicator taxa. From the calibration models and the linear relationship between altitude and epilimnetic water temperature, the average lake water temperature can be predicted with an accuracy of 3.2°C. After further refinement, a transfer function for palaeotemperature based on diatoms would be of potential value for climatic reconstructions in tropical regions.
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  • 5
    ISSN: 1573-0417
    Keywords: palaeolimnology ; diatoms ; meromixis ; lakeontogeny ; human disturbance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Three meromictic lakes in the World Heritage Area of south-west Tasmania possess unusual microbiological communities. Their meromixis is maintained by periodic incursions of brackish water from the nearby Gordon River which, in its lower reaches, is a salt-wedge estuary. In 1977 the construction of a dam in the middle reaches of the river restricted penetration of the salt-wedge and meromixis rapidly declined in all three lakes. A palaeolimnological study was carried out on one of the lakes, Lake Fidler, firstly to determine the history of meromixis and its associated microbiological communities, and secondly to assess whether the recent and rapid decline of meromixis is inconsistent with natural rates of development of the Gordon River meromictic lakes. One part of this study included the analysis of the stratigraphy of fossil diatoms from a 17-metre sediment core dating back 8000 yrs. Detrended Correspondence Analysis and Analog Matching were used to compare diatom species assemblages in core samples with diatom samples from a reference dataset consisting of a selection of lake and river sites in the lower Gordon River valley. Five distinct stratigraphic zones were identified in the core. These zones indicated specific stages in the development of the Gordon River lakes from river backwaters to ectogenically-maintained meromictic lakes which will, finally, become terrestrialised by encroaching rainforest. The onset of a stratified water column was identified by the emergence of a dominant freshwater algal flora which suggested that the lake had developed a mixolimnion and become meromictic ca. 2070 ± 50 14C yrs ago. In the context of this long history of meromixis, the rapid demise in meromictic stability following construction of the dam is judged to be inconsistent with natural rates of development. The palaeolimnological studies, of which this paper is one part, prompt recommendations for a management strategy to prevent the further decay of these meromictic lakes in the World Heritage Area.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5117
    Keywords: heterotrophic nanoflagellates ; ciliates ; rotifers ; bacteria ; microbial food web ; tidal river ; estuary ; Schelde
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Freshwater tidal estuaries comprise the most upstream reaches of estuaries and are often characterised by the presence of dense bacterial and algal populations which provide a large food source for bacterivorous and algivorous protists. In 1996, the protistan community in the freshwater tidal reaches of the Schelde estuary was monitored to evaluate whether these high food levels are reflected in a similarly high heterotrophic protistan biomass. Protistan distribution patterns were compared to those of metazoan zooplankton to evaluate the possible role of top-down regulation of protists by metazoans. Apart from the algivorous sarcodine Asterocaelum, which reached high densities in summer, heterotrophic protistan biomass was dominated by ciliates and, second in importance, heterotrophic nanoflagellates (HNAN). HNAN abundance was low (annual average 2490 cells ml−1) and did not display large seasonal variation. It is hypothesised that HNAN were top-down controlled by oligotrich ciliates throughout the year and by rotifers in summer. Ciliate abundance was generally relatively high (annual average 65 cells ml−1) and peaked in winter (maximum 450 cells ml−1). The decline of ciliate populations in summer was ascribed to grazing by rotifers, which developed dense populations in that season. In winter, ciliate populations were probably regulated `internally' by carnivorous ciliates (haptorids and Suctoria). Our observations suggest that, in this type of productive ecosystems, the microbial food web is mainly top-down controlled rather than regulated by food availability.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 336 (1996), S. 107-120 
    ISSN: 1573-5117
    Keywords: tropics ; freshwater algae ; Indo-Malaysia North Australia ; geographic distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The present knowledge of the freshwater algal flora in the Indo-Malaysian North Australian region is reviewed. More than 4700 taxa have been recorded from this region. Desmids, diatoms and cyanobacteria are among the better studied groups of organisms, while phytoflagellates have received very little attention. Phytoplankton communities in tropical lakes are generally similar to summer communities of temperate lakes. In addition, there is a large number of typical tropical taxa, including pantropical and regional endemic elements. Local endemism occurs in the old Tertiary lakes of the region. The composition of algal communities changes markedly along an altitudinal gradient, and tropical taxa are gradually replaced by taxa characteristic for cool climatic conditions. Biogeographical distribution patterns are exemplified for the desmids and diatoms. Among the more than 2680 desmids recorded from the Indo-Malaysian North Australian region, about 800 have never been found elsewhere. Dispersal by migratory birds and past climatic changes might explain distribution patterns. Because of incomplete taxonomy and a general lack of understanding of the autoecology, distribution and speciation of freshwater algae, however, there remain serious obstacles for detailed biogeographical analyses.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 234 (1992), S. 175-193 
    ISSN: 1573-5117
    Keywords: Papua New Guinea ; tropical waters ; diatoms ; TWINSPAN classification ; DCA ordination ; environmental factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The benthic and periphytic diatom flora is studied in 136 fresh waters in Papua New Guinea. DCA ordination and TWINSPAN are used to describe 20 diatom assemblages. Conductivity, water temperature and altitude are the main sources for the variation in the data.
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  • 9
    ISSN: 1573-5117
    Keywords: Surirella sparsipunctata ; Lake Tanganyika
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three populations of S. sparsipunctata from the eastern coast of Lake Tanganyika were studied by light and electron microscopy. We found no distinct differences between the type variety and var. laevis; therefore we propose to include the var. laevis with the typical variety. An amended description of S. sparsipunctata based on LM and SEM observations is given.
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  • 10
    Publication Date: 2024-04-20
    Description: This dataset contains paired optical and biogeochemical properties sampled in the Belgian Coastal Zone and inland waters of Flanders, Belgium, for the growth season period (March to October) of 2017, 2018, and 2019. This dataset was collected to support: (1) development and validation of hyperspectral algorithms for aquatic retrievals with in situ instrumentation; (2) development and validation of hyperspectral algorithms for aquatic retrievals with Earth Observation; (3) development and validation of multispectral algorithms and aquatic applications to high spatial resolution sensors. The data were collected over a series of short campaigns, with variable frequency depending on the water system and sampling year. The systems sampled were lakes, a lagoon, an estuary and coastal waters. The data consist of three types of data: I - Inherent Optical Properties: - Spectral CDOM absorption coefficient (〈 0.45 μm; cuvette): (A) Measured, (B) Fitted to hyperbolic model, (C) Hyperbolic slope; - Spectral particle absorption coefficient (〉 0.7 μm; filterpad inside integrating sphere): (A) Measured; - Spectral de-pigmented particle absorption (ad) coefficient (〉 0.7 μm; chemical oxidation): (A) Measured, (B) Fitted to exponential model, (C) Exponential slope; - Spectral in vivo pigment absorption coefficient (〉 0.7 μm; calculated by difference): (A) From measured ad, (B) From fitted ad; - Spectral particle scattering coefficient (acceptance angle of 0.074 degrees): (A) Measured, (B) Compensated to equivalent 0.018 degree acceptance angle; - Spectral particle beam attenuation coefficient (acceptance angle of 0.074 degrees): (A) Measured, (B) Compensated to equivalent 0.018 degree acceptance angle; - Near-forward particle volume scattering function (laser diffraction at 670 nm): (A) Measured with a LISST-100X, (B) Measured with a LISST-200X; - Turbidity (side-scattering, NIR): (A) Measured; II - Apparent Optical Properties: - Lambert-equivalent substrate bi-hemispherical reflectance (spectrometer and imaging spectrometer): (A) Measured; - Lambert-equivalent water-leaving bi-hemispherical reflectance (Above water and on-water methods): (A) Estimated or measured, compensated for instrument self-shadowing; - Secchi disk depth: (A) Measured, (B) Compensated for the Sun elevation; III - Biogeochemical properties: - Suspended particulate matter (SPM) concentration (〉 0.7 μm; gravimetric method): (A) Measured; - Mineral fraction of the SPM (〉 0.7 μm; thermal oxidation, gravimetric method): (A) Measured; - Particle size distribution (laser diffraction): (A) Volume concentration from LISST-100X, (B) Volume concentration from LISST-200X; - Apolar pigment concentration (〉 0.7 μm; HPLC): (A) Mass concentration; - Bottom cover classification (visual description): (A) Observed in situ; - Phytoplankton counts (55 µm to 300 µm; flow imaging microscopy): (A) Measured; - Amplicon sequencing of phytoplankton (〉 0.7 μm; Illumina): (A) Spuikom lagoon, (B) Belgian Coastal Zone;
    Keywords: Apparent optical properties; biogeochemical data; Exploiting very high resolution satellite imagery for coastal and inland water monitoring; HYPERMAQ; Hyperspectral and multi-mission high resolution optical remote sensing of aquatic environments; inherent optical properties; LifeWatch_BE; LifeWatch BE; Phytoplankton composition; PONDER
    Type: Dataset
    Format: application/zip, 1.7 MBytes
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