Lake Velencei Research Articles

Determination of glyphosate residues in Hungarian water samples by immunoassay

An enzyme-linked immunosorbent assay (ELISA) for the detection of glyphosate was investigated for assay performance characteristics and was applied for determination of glyphosate contamination levels in selected surface and ground water resources in Hungary in 2010 and 2011. Advantages of the method include its simplicity (no laborious extraction) and specificity (cross-reactivity is below 0.1% for related compounds, e.g. aminomethyl-phosphonic acid, glufosinate). On the basis of our experiments, the practical limit of detection (LOD) ranged between 0.05 and 0.12ng/ml. The standard curve was of sigmoid (logistic) characteristics, and it co-occurred with curves obtained for spiked surface water samples. Matrix effects were observed in tap water, possibly due to chlorination and/or heavy metal ions, e.g. copper and zinc. The method was applied for the analysis of 42 surface and ground water samples collected from Békés county in Hungary at 14 sampling sites in 2010 and 18 surface water samples collected from the Danube River and Lake Velencei in Hungary at 12 sampling sites in 2011. Exceedingly high glyphosate levels (nearly 1ng/ml) were measured in 5 samples, and significant concentrations were determined in 16 cases (0.54–0.76ng/ml) in 2010, while practically no contamination was found in 2011. The great contrast between the two sampling regimes is explained by differing agricultural locations, natural precipitation and, to a greater extent, catchment area characteristics, resulting in varying leaching or run-off of glyphosate to surface waters.

Diversity of Sulfate-Reducing Bacteria Inhabiting the Rhizosphere of Phragmites australis in Lake Velencei (Hungary) Revealed by a Combined Cultivation-based and Molecular approach

The community structure of sulfate-reducing bacteria (SRB) associated with reed (Phragmites australis) rhizosphere in Lake Velencei (Hungary) was investigated by using cultivation-based and molecular methods. The cultivation methods were restricted to recover lactate-utilizing species with the exclusion of Desulfobacter and some Desulfobacterium species presumably not being dominant members of the examined community. The most-probable-number (MPN) estimations of lactate-utilizing SRB showed that the cell counts in reed rhizosphere were at least one order of magnitude higher than that in the bulk sediment. The number of endospores was low compared to the total SRB counts. From the highest positive dilution of MPN series, 47 strains were isolated and grouped by restriction fragment length polymorphism (RFLP) analysis of the amplified 16S ribosomal RNA (rRNA) and dsrAB (dissimilatory sulfite reductase) genes. Contrary to the physiological diversity of the isolates, the combined results of RFLP analysis revealed higher diversity at species as well as at subspecies level. Based on the partial 16S rRNA sequences, the representative strains were closely affiliated with the genera Desulfovibrio and Desulfotomaculum. The partial dsrAB sequences of the clones, recovered after isolation and PCR amplification of the community DNA, were related to hitherto uncultured species of the genera Desulfovibrio and Desulfobulbus. Nevertheless, the representative of the second largest clone group was shown to be closely affiliated with the sequenced dsrAB gene of a strain isolated from the same environment and identified as Desulfovibrio alcoholivorans. Another clone sequence was closely related to a possible novel species also isolated within the scope of this work.

Cultivable bacterial composition and BIOLOG catabolic diversity of biofilm communities developed on Phragmites australis

Biofilm samples formed on submerged young and old stems of reed, Phragmites australis (Cav.) Trin ex Steudel were taken during summer at different sites of Lake Velencei, Hungary. BIOLOG GN microplates were used to analyze the patterns of sole carbon source utilizations by microbial communities. From the carbon sources, carbohydrates and amino acids were preferred by all microbial communities. In the case of the old reed stem samples, higher number of carbohydrates, carboxylic acids and polymers were used than in young samples. Biofilm bacterial communities from the old reed samples of the nature conservation area of the lake used the highest number of (≥50% of the available) substrates. In principal component analysis (PCA), the metabolic potential of the microbial communities from the middle open water region of the lake showed the smallest variability. The variability within metabolic potential of the reed stem microbial communities from a given sampling site was the largest in the case of samples originating from the western, reed-covered nature conservation area. A total of 251 bacterial isolates obtained after serial dilutions and plating onto different media were characterized by traditional phenotypic tests. The strains showed high activities mainly in the hydrolysis of certain biopolymers (gelatine and casein). PCA was used to evaluate the phenotypic variability of strain groups of different sampling sites. The two open water regions were similar to each other, and separated from the western reed covered part of the lake. Similarly to the BIOLOG community-level physiological profiles, strain groups of the young and old reed stem samples originating from the nature conservation area had the largest metabolic potential. On the basis of 16S rDNA sequence analysis, 23 representative strains with different ARDRA patterns were identified. The cultivation-based investigations of bacterial diversity showed characteristic differences in the number of identified taxa in connection with the sampling sites. No characteristic differences could be observed according to medium or sample type (young, first year and more than 1-year old stems) among the identified species. 16S rDNA sequence comparisons resulted in the identification of the genera Aureobacterium, Arthrobacter, Kocuria, Microbacterium, Micrococcus, Rhodococcus, Bacillus, Marinibacillus, Rhodobacter, Defluvibacter, Pseudomonas, Klebsiella, Serratia and Aeromonas. The results of the cultivation-based and BIOLOG investigations revealed characteristic differences in the bacterial community composition and activities of the open water region and the reed covered nature conservation part of the lake.

Comparative algological and bacteriological examinations on biofilms developed on different substrata in a shallow soda lake

According to the European Water Framework Directives, benthic diatoms of lakes are a tool for ecological status assessment. In this study, we followed an integrative sample analysis approach, in order to find an appropriate substratum for the water qualification-oriented biomonitoring of a shallow soda lake, Lake Velencei. Six types of substrata (five artificial and one natural), i.e., andesite, granite, polycarbonate, old reed stems, Plexiglass discs and green reed, were sampled in May and in November. We analysed total alga and diatom composition, chlorophyll a content of the periphyton, surface tension and roughness of the substrata and carbon source utilisation of microbial communities. Water quality index was calculated based on diatom composition. Moreover, using a novel statistical tool, a self-organising map, we related algal composition to substratum types. Biofilms on plastic substrates deviated to a great extent from the stone and reed substrata, with regard to the parameters measured, whereas the biofilms developing on reed and stone substrata were quite similar. We conclude that for water quality monitoring purposes, sampling from green reed during springtime is not recommended, since this is the colonization time of periphyton on the newly growing reed, but it may be appropriate from the second half of the vegetation period. Stone and artificially placed old reed substrata may be appropriate for biomonitoring of shallow soda lakes in both spring and autumn since they showed in both seasons similar results regarding all measured features.

Metabolic Activity and Phylogenetic Diversity of Reed (Phragmites australis) Periphyton Bacterial Communities in a Hungarian Shallow Soda Lake

In the present study, the species composition and potential metabolic activities of bacterial communities of reed Phragmites australis (Cav.) (Trin. ex Steudel) periphyton from Lake Velencei were studied by cultivation-based and metabolic fingerprinting methods. Serially diluted spring biofilm samples were used to test the community-level physiological profiling (CLPP) using BIOLOG microplates, and for plating onto different media. On the basis of their morphological, biochemical, and physiological test results, 173 strains were clustered by numerical analysis. Representatives of amplified ribosomal DNA restriction analysis (ARDRA) groups were identified by their 16S rDNA sequence comparison. Based on the results of the CLPP investigations, regional differences were detected among the utilized substrate numbers and types, parallel with the increase in incubation time. The phenotypic test results of the strains showed considerable variability with respect to the sampling sites and the media used for cultivation. The most frequently isolated strains were identified as members of genera Agrobacterium, Pseudomonas (P. anguilliseptica, P. marginalis, P. alcaligenes, P. fragi) with aerobic or facultative anaerobic respiratory metabolism, and the species Aeromonas sobria and A. veronii with strong facultative fermentative metabolism. Other strains were identified as Gram-positive Arthrobacter, Bacillus, and Kocuria species. The rarely isolated strains were members of beta-Proteobacteria (Acidovorax, Delftia, Hydrogenophaga, and Rhodoferax), gamma-Proteobacteria (Psychrobacter and Shewanella), low G + C Gram-positives (Brevibacillus, Paenibacillus, and Exiguobacterium) and high G + C Gram-positives (Aureobacterium and Microbacterium).

TREBACOSA EUROPAEA, A NEW WOLF SPIDER FROM HUNGARY (ARANEAE, LYCOSIDAE)

Abstract A new species of Lycosidae, Trebacosa europaea, is described from male specimens collected within reed beds of Lake Velencei from Hungary. The species represents the Palearctic sister species of the Nearctic Trebacosa marxi (Stone 1890), and occurs in a very specialized habitat of Phragmitetum communis.

Phenotypic characterization and molecular taxonomic studies on Bacillus and related isolates from Phragmites australis periphyton

Reeds may play important role in the self-purification of aquatic habitats due to the filtration capacity and their periphyton communities developing on the underwater plant surfaces. The efficiency of this process and the transformation of organic substances can be influenced by the species composition and activity of microbial communities, including Bacillus and related species. For cultivation based bacteriological examinations reed periphyton samples were collected from 30 cm beneath the water surface of Lake Velencei and the Soroksár Danube branch (Hungary). After a primary selection 40 Bacillus and related strains were investigated by traditional morphological, biochemical tests, API 20E, API 50CHB and BIOLOG GP2 systems, and identified by 16S rDNA sequence comparison. The isolated strains were characterized by wide biochemical activity spectrum (i.e., the metabolism of carbohydrates and biopolymers) as well as widespread ecological tolerance based on their NaCl and pH range investigations. Species with facultative alkaliphilic features ( Marinibacillus marinus, Bacillus firmus) were detected only from the reed biofilm of Lake Velencei, while alkalitolerant Bacillus and related species from both sampling sites. 22 endospore-forming strains were identified as members of species B. cereus, B. firmus, B. flexus, B. licheniformis, B. megaterium, B. muralis, B. pumilus, B. subtilis and Marinibacillus marinus. Only one species, with 95–96% sequence similarities to B. pumilus was found to be common among the strains from Lake Velencei and the Soroksár Danube branch. Altogether, 18 strains could not be identified as known species of Bacillus, Brevibacillus and Paenibacillus, hence they may represent new bacterial taxa.

Spatial analysis of mortality caused by malignant tumors, especially by digestive system tumors, using empirical Bayes estimates in Fejér County, Hungary

General practitioners in the vicinity of Lake Velencei in Fejér County, Hungary, have reported an unusual pattern of recent cancer mortality. Our aim was to clarify whether the presumed mortality cluster is epidemiologically justified; whether it is restricted to the locations in question or also appears elsewhere in the county; and if it is associated with some particular disease group. County mortality from malignancies of the digestive system, other malignancies, and all other causes for the period 1994 to 1999 was analyzed in 15- to 64-year-old men and women, using conventional standardized mortality ratios and empirical Bayes estimates. A continuous surface was interpolated from settlement level data for mortality maps. A mortality cluster from men's digestive cancers is apparent north and east of Lake Velencei and also elsewhere in the county. Differences from the country average in the frequency of males' deaths from other malignancies are fairly limited. A number of problematic areas in men's mortality from other causes are identifiable, including some of the settlements under the primary focus. Women's digestive tract cancer mortality in the area of the men's cluster near Lake Velencei is below the national average. There are almost no differences from the country level in women's deaths from other malignancies. Female mortality from all other causes shows remarkable elevations in the south of the county. Our results suggest the possible role of geographically localized exposures. Men's high mortality from digestive tract cancers is a problem affecting a considerable area of the county, necessitating further investigation. Continued search for causes is also warranted by some estimates of exceptionally high death rates in women from causes other than malignancies.

Rhizome-associated bacterial communities of healthy and declining reed stands in Lake Velencei, Hungary

Lake Velencei is a shallow soda lake with extensive reed coverage. In this study, the bacterial communities of reed (Phragmites australis (Cav.) Trin. ex Steudel) rhizomes from healthy and declining stands were compared. Inner and outer rhizome surfaces were sampled. Samples were plated and isolated in September 1998 and June 1999. Phenotypic data of 371 bacterial strains were used for cluster analysis. Identification of phena was based on partial 16S rDNA sequence analysis of representative strains. Healthy reed stand rhizomes in fall 1998 were dominantly colonised by facultatively fermentative organisms, like Erwinia billingiae, Aeromonas sobria, Pantoea agglomerans, and Pseudomonas azotoformans. In the June 1999 sample, mainly Kocuria rosea and various Bacillus spp. dominated. In declining stands of September 1998, a saprotrophic community was found: Acinetobacter spp., Aeromonas hydrophila, Curtobacterium luteum, Agrobacterium vitis, and two further groups representing presumably new taxa. In June 1999, reed rhizomes were colonised by Kocuria rosea, but Dietzia maris and Bacillus cohnii could be isolated as well. Healthy and declining reed stand rhizomes can be distinguished based on the culturable bacterial community. No obligately plant pathogenic bacteria were found, however the possibility of a local, opportunistic bacterial invasion can not be ruled out (e.g. Curtobacterium). The presence of potentially beneficial bacterial species was demonstrated in the healthy reed rhizome rhizosphere (e.g. Pseudomonas azotoformans, Pantoea agglomerans).

Long-term investigations on the changes of the MPN values of bacterial communities participating in the sulphur cycle in Lake Velencei, Hungary

Lake Velencei is a shallow lake with a fairly variable water quality due to the effect of the earlier basin reconstruction and external factors, such as the weather and the organic matter loading from the catchment areas. For studying the changes in sediment of Lake Velencei, MPN technique, based bacteriological investigations, as well as measurements of water chemical parameters were performed. Microbial communities of aerobic thiosulphate-oxidising, anaerobic phototrophic, and sulphate-reducing bacteria taking part in the sulphur cycle were monitored between 1993 and 2001. In the western part of the lake the bacteriological results and the chemical parameters verified the presence of sulphuretum. In the first low water period of the studies the quantity of the bacteria contributing to the sulphur cycle was low in the sediment. After the increase of the water level the distribution of these microbes became somewhat homogeneous in the sediment. However, the different sediment regions might be characterised with dissimilar MPN values of the studied bacterial communities.

Bacterial activities in the sediment of Lake Velencei, Hungary

Lake Velencei (Hungary) is one of the westernmost shallow soda lakes, extending from Eastern Europe to the Carpatian basin. The spatial and temporal distribution of the sediment microbiota, the metabolic potential of bacterial communities and the species composition of the genera Bacillus and Clostridium, as well as sulphate-reducing bacteria (SRB) were investigated regarding the close interactions between the lake sediment and the overlaying water column, the special water chemical parameters, and the extensive reed coverage of the lake. Aerobic microbial activities were tested with community-level physiological profiling (CLPP) using BIOLOG microplates. The quantification of the anaerobic fermentative and sulphate-reducing bacteria was done by the MPN (Most Probable Number) method. The cultivation of bacteria adapted to the special physico-chemical characteristics of the lake was carried out employing selective media. Multivariate analysis of CLPP data indicated that the microbial communities of the sediment separated from that of the water and showed seasonal variations of the utilised carbon sources. The results of the MPN demonstrated that the counts of the fermentative and sulphate-reducing bacteria in the reed rhizosphere were about one order higher than in the sediment. Among the isolated bacterial strains, a large number were characterised as facultative or obligate alkaliphilic and also moderately halophilic. The partial sequencing of 16S rDNA of the selected representatives resulted in species of aerobic bacteria, such as Bacillus pseudofirmus, B. halmapalus, B. cohnii, B. (Marinibacillus) marinus, and anaerobes, such as Clostridium putrificum – sporogenes, C. scatologenes, C. bifermentans, Desulfotomaculum guttoideum, Desulfovibrio alcoholivorans, and Desulfovibrio burkinensis.

Algological and bacteriological investigations on reed periphyton in Lake Velencei, Hungary

In the shallow Lake Velencei (surface area 24.5 km2) reed communities (Scirpo-Phragmitetum) are of great significance due to extensive metabolic activity of algal-bacterial associations developing on their submerged surfaces. Samples for algological and bacteriological studies were taken in April 2000 and July 2001 at five sites of the lake and were analysed with traditional methods as well as with tools of molecular biology (16S rDNA sequencing). These investigations have shown that (i) The original mosaic structure of the lake disappeared; periphytic algae became spatially uniform both in terms of taxonomic composition and abundance. (ii) The biodiversity of the reed periphyton decreased. The dominance of the weed algal species Achnanthes minutissima Kutz. increased significantly. (iii) The most frequent bacteria were members of the genera Pseudomonas, Acinetobacter, Shewanella and Agrobacterium characterised by oxidative chemoorganotrophic heterotrophic- and Aeromonas and Bacillus species with fermentative metabolism. (iv) Among the studied bacterial strains both plant growth promoting bacteria, members of Pseudomonas fluorescens group, and potential plant pathogens (Agrobacterium, Aureobacterium, Curtobacterium) were present.

ToxicMicrocystis aeruginosa in Lake Velencei

Lake Velencei is a shallow lake in Hungary. The first cyanobacterial bloom of Microcystis aeruginosa appeared in the lake in 1991. This cyanobacterial species was also found earlier but blooms were not recorded. The toxins of M. aeruginosa were studied in Lake Velencei in 1992. The present study deals with the toxicity of a M. aeruginosa biomass of different origin detected by intraperitoneal (ip.) mouse assay, Thamnotoxkit F™ microbiotest, and toxin analysis by high-performance liquid chromatography (HPLC). The biomass was collected by plankton net and the isolated strains were cultured from sediments and from bloom material. Minimal lethal doses (MLD) by ip. mouse assay ranged from 20 to 50 mg/kg−1. Comparing the results from 1992 and 1997–1998, no change in the toxicity of M. aeruginosa was detected. According to the HPLC analysis the combination of microcystins varied in a narrow range with microcystin-LR found in each sample. The cyanobacterial blooms caused by M. aeruginosa in Lake Velencei considerably decreased, though it remained in the sediment with the same toxicity. The Thamnotoxkit F™ microbiotest was an alternative method for detecting the cyanotoxins. © 2000 John Wiley & Sons, Inc. Environ Toxicol 15: 554–557, 2000

Comparison of succession of reed periphyton in a degraded and in an undisturbed part of a shallow lake (Lake Velencei, Hungary, Central Europe)

The decay of the influence of reeds on the succession of algae coating them was stuided. In the same lake, and at very close places, periphyton colonization was found to be significantly different. At a ’degraded’ point, the quantity of algae fluctuated with respect to both biomass and the number of individuals. The number of taxa was low in the first three weeks and began to grow only in the fourth week. The dominant species were also different.

Fejér county—the István Király Museum at Székesfehérvár

Fejer county lies between Budapest and Lake Balaton; the county's chief town, Szekesfehervar, has played a prominent role in Hungarian history and, since the 1960s, has also been gaining in importance as an industrial centre. Dunaujvaros, the county's other principal town, developed in the 1950s in the vicinity of the steel works and was the first example of socialist town-planning in Hungary. In the northern part of the county, where lie the Bakony, Vertes and Velence hills, the villages populated by national minorities retain their special character and mining and vine-growing are practised. In the southern part of the county lies the agricultural plain of Mezőfőld, as well as Lake Velencei, which is visited regularly by more than 100,000 holiday-makers at the height of summer; here the extensive highway system bears witness to the importance of this area from the Roman period until the early Middle Ages. Late in the tenth century Szekesfehervar became the royal residence of the Hungarian kings, who were crowned and buried there, and the Diet even met there for a long period. After the Ottoman domination the town's political importance decreased, but up to the mid-nineteenth century Szekesfehervar remained an important centre of Hungarian cultural life.

Investigation of Hungarian Lakes by means of Landsat data

Lake Balaton is an important recreational area not only in Hungary but in Central-Europe as well. In the last decades due to increased tourism, industrial and agricultural activity the eutrophication of the lake is subject of serious considerations. The usual chlorophyll-a content measurements for the whole lake are rather expensive and time consuming and do not give enough information for an overall picture of water quality. A good correlation (r > 0.9) has been found between the reflectivities measured by Landsat MSS in the visible bands and the chlorophyll-a values derived from water samples (taken not exactly on the day of imaging) when the meteorological conditions between the date of imaging and sampling, and the sampling site selection were favourable. Based on this correlation the chlorophyll-a map of Lake Balaton is presented for a given date. The infrared bands of Landsat are useful to map the distribution and spreading of macrophytes in shallow waters, as Lake Velencei is. The conclusion is that Landsat data can be used to monitor lake water quality changes, but simultaneous calibration measurements on properly selected sampling sites are necessary.