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Example of a microautoradiogram of auto fl uorescent picocyanobacteria from OS after the addition of 180 nM 3 H-
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Dilute soda lakes are among the world's most productive environments and are usually dominated by dense blooms of cyanobacteria. Up to now, there has been little information available on heterotrophic bacterial abundance, production, and their controlling factors in these ecosystems. In the present study the main environmental factors responsible f...
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... The conductivity was highly correlated with salinity ( r s = 0.89, p < 0.001) and alkalinity ( r s = 0.63, p < 0.001) and was a good indicator for the evaporative concentration. Salinity varied from 2.4 g L ) 1 to 31.3 g L ) 1 (Table 1) and was dominated by chloride, sulfate, carbonate, and bicarbonate anions and sodium cations. The proportion of the carbonate and bicarbonate anions comprised up to 60% of total salinity (data not shown) and was responsible for the observed high pH values up to 10.89 in the pools. The high alkalinity (Fig. 2B) was in turn responsible for the relatively low calcium and magnesium concentrations with mean values of 47 mg L ) 1 and 148 mg L ) 1 , respectively. The peak of conductivity and alkalinity in spring 2000 at US was observed when the part of the US which was used as sampling site for the fi rst four sampling dates desiccated and thereafter an adjacent sampling site was chosen. DOC values and conductivity were highly signi fi cantly correlated ( r s = 0.80, p < 0.001). The highest DOC value coincided with the highest conductivity value in ZL before complete evaporation (Fig. 2C). Chlorophyll a values ranged from 0 to 430 ng L ) 1 with the lowest concentration in the ZL (annual average: 8.2 l g L ) 1 ) and the highest concentration in LL (annual average: 197 l g L ) 1 ; Table 1). Cyanobacterial numbers ranged from 0 to 307 · 10 cells L ) 1 with highest values observed at OS and LL in early August 2000 and early May 2001, respectively. US exhib- ited two peaks with values of more than 170 · 10 9 cells L ) 1 in July and September (Fig. 3A). ZL and WL featured the lowest median cyanobacterial numbers (Table 2). During the winter months cyanobacterial numbers were low (<10 · 10 9 cells L ) 1 ) in all pools except for LL in February, where numbers of 54 · 10 9 cells L ) 1 were observed. Cyanobacteria were dominated by unicellular Synechococcus species and fi lamentous forms belonging to the genus Cyanospira . Colony-forming species were frequently observed after long periods of stable weather conditions (personal observation). However, the phytoplankton consisted not only of cyanobacteria, whose numbers explained 36% of the chlorophyll a variation, but also of diatoms and euglenoids. In all pools two peaks of bacterial numbers occurred in early and late summer with values up to 270 · 10 9 cells L ) 1 (Fig. 3B). Low numbers (<40 · 10 9 cells L ) 1 ) were observed after a strong decrease in July and during the whole winter season. A subjection of the dataset to a Kruskal – Wallis test revealed that the fi ve soda pools were statisti- cally different in bacterial ( v = 27, p < 0.001) and cyanobacterial numbers ( v 2 = 41, p < 0.001). Bacterial and cyanobacterial numbers were consistently greater in the soda pools with higher concentrations of total suspended solids (Tables 1 and 2) as indicated by Tukey tests and by highly signi fi cant positive correlations of TSS with bacterial numbers ( r s = 0.76, p < 0.001) and cyanobacterial numbers ( r s = 0.78, p < 0.001), which were also signi fi cantly intercorrelated ( r = 0.85, p < 0.001). From all performed saturation experiments ( n = 10) a mean half-saturation constant ( K m ) of 31.8 nM leucine (SE: 2.5 nM) was calculated and further used to calculate the maximal leucine uptake ( V max ) from the leucine incorporation rates ( V ) at 60 nM ( S ) for all other sampling dates. In all experiments production rates reached saturation at a concentration of 180 nM (data not shown). Rates of bacterial production ranged over three orders of magnitude during the investigation period, from 1 to 738 l g L ) 1 h ) 1 (Table 2). The annual maximal BSP rates were measured at OS, US, and LL in the middle of July, coinciding with a strong decrease in bacterial numbers and temperature. However, highly signi fi cant positive correlations of BSP with bacterial numbers ( r s = 0.59, p < 0.001) and temperature ( r s = 0.58, p < 0.001) were found, as well as with total suspended solids ( r s = 0.47, p < 0.001) and DOC ( r s = 0.45, p < 0.001). At all sites high rates >30 l g C L ) 1 h ) 1 of bacterial secondary production were measured from April to October, when water temperature was mostly above 20 ° C. With one exception (January, LL) low rates <30 l g C L ) 1 h ) 1 were recorded from November to March. Over the year, the rates of bacterial production were not statistically different between the fi ve study sites, as indicated by Kruskal – Wallis test ( v 2 = 4.5, p > 0.1). The speci fi c growth rates of the bacterioplankton in the fi ve pools varied strongly over the seasons from 0.004 to 1.65 h ) 1 (Table 2) corresponding to doubling times of 8 days and 25 min, respectively. The microautoradiography experiments showed that the majority of silver grains in the leucine autoradiograms were associated with bacteria (data not shown). In all incubations with [ 3 H]leucine only a small fraction (<0.5%) of silver grains was associated with cyanobacteria (Fig. 4), suggesting that even a high cyanobacterial biomass hardly biased the measurements of bacterial secondary production in the fi ve saltwater pools. ‘‘ Labeled ’’ bacteria were determined once for each habitat, ranging from 40% (OS) to 90% (WL) of all DAPI-stained bacteria (data not shown). These results represent mini- mum estimates of the percentage of active cells in the fi ve studied pools, because leucine was probably not utilized by all bacteria. In order to elucidate the main environmental factors describing the systems of the fi ve soda pools, a PCA of the whole data set was performed. Four principal components (PC) with an eigenvalue >1 were extracted (Table 3, Fig. 5). PC 1 explained 45.2% of the observed variance and consisted of inorganic and organic suspended solids, total phosphorus, chlorophyll a , and bacterial and cyanobacterial numbers. PC 2 explained 17.3% of the observed variance and contained salinity, conductivity, and DOC. PC 2 contained also the variable wind with a negative sign, which can be interpreted that in periods with high evaporative concentration the weather situation is mostly calm and viceversa. PC 3 (temperature and BSP) and PC 4 (alkalinity and pH) were of less importance, explaining only 10.0 and 7.6% of the variance, respectively. PC 1 can be described as a turbidity factor as it includes all par- ticulate variables. However, it should be mentioned that the variables chlorophyll a and cyanobacterial numbers represent the manifested result of primary productivity, which is tightly coupled to the annual light cycle and which can be seen as an integrated component of PC 1. PC 2, on the other hand, can be described as a concentration factor as it contains all dissolved variables. The PCAs of the single pools showed slightly diverging pictures than the PCA performed with the whole data set (Table 4). PC 1 and PC 2 could be described as the turbidity factor and concentration factor, together explaining more than 56% and 73% in OS and US, respectively. At ZL, PC 1 included both the turbidity and the concentration factor, explaining 55% of the total variance alone, and PC 2 consisted of total phosphorus and alkalinity. A strong biotic component (PC 2) explaining 20% of the total var- iance was found at LL, whereas PC 1 (33% explained variance) is interpreted as a combination of suspended solids and phytoplankton. The turbidity and the concentration factor were of inverted importance in WL. PC 1, explaining 52% of the observed variance, additionally included BSP, chlorophyll a , and total phosphorus. The soda pools of the national park Neusiedler See — Seewinkel appear to be sites of extremely high microbial activity and biomass. In past studies on hypertrophic aquatic environments highest bacterial numbers up to 356 · 10 9 L ) 1 were reported by Kilham [16] for African alkaline lakes. Grant et al. [12] reported that aer- obic heterotrophic bacteria can reach numbers of 100 · 10 9 L ) 1 in dilute soda lakes, and Zinabu and Taylor [42] found maximal bacterial numbers of 117 · 10 9 L ) 1 in a variety of different Ethiopian soda lakes. These values are thus of the same magnitude as our measurements (Table 5). Ecosystems similar to the Austrian soda pools exist in Eastern Europe, Russia, and East Africa, but to the best of our knowledge no information is available on heterotrophic bacterial production and growth rates. The highest BSP rates found in the literature, up to 129 l g C L ) 1 h ) 1 , were reported by Boon [5] for the Australian billabongs — values which were far exceeded by our measurements. White et al. [42] reported maximal l values of 0.36 h ) 1 for freshwater ecosystems and 1.28 h ) 1 for saltwater habitats, which also included data from an arti fi cial aquaculture pond. In Table 5 ecosystems are listed which exhibit similarities to the Austrian soda pools in salinity, trophy, depth, turbidity, and/or alkalinity. With the exception of Big Soda Lake, all of the mentioned environments are shallow and highly productive. The study of Big Soda Lake was chosen because it provides the only data on bacterial production in aquatic alkaline environments. The presented environments in Table 5 exhibit signi fi cantly lower bacterial production and growth rates than in this study, except for the Indus River Delta: Bano et al. [3] reported an unprecedented bacterial growth rate of 1.0 h ) 1 for a natural assemblage, coinciding with a dense cyanobacterial bloom. For the East African soda lakes it is conceivable that growth rates of magnitude similar to those observed for the Austrian soda pools may be en- countered, but no data are available. We suppose that the combination of shallowness, the existence of growing algal blooms, and high temperature is probably the driving factor enabling growth rates of l ‡ 1. The extremely high speci fi c growth rates of up to 1.65 h ) 1 , corresponding to doubling times of 25 min, suggest that bacterioplankton in the pools has the ...
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... Physical and chemical parameters, total suspended solids, water level and discharge data At the samplings, the water temperature, pH, electrical conductivity and oxygen concentration values were measured on site with the handheld multi-parameter meter Multi 3430 (WTW, Xylem Analytics, Germany). Total suspended solids (TSS) and inorganic particulate matter were determined during the annual cycle according to Eiler et al. (2003). Water discharge and level data were obtained from national monitoring systems for the sampling site (https:// www. ...
Epilithic biofilms are ubiquitous in large river environments and are crucial for biogeochemical processes, but their community structures and functions remain poorly understood. In this paper, the seasonal succession in the morphological structure and the taxonomic composition of an epilithic bacterial biofilm community at a polluted site of the Danube River were followed using electron microscopy, high-throughput 16S rRNA gene amplicon sequencing and multiplex/taxon-specific PCRs. The biofilm samples were collected from the same submerged stone and carried out bimonthly in the littoral zone of the Danube River, downstream of a large urban area. Scanning electron microscopy showed that the biofilm was composed of diatoms and a variety of bacteria with different morphologies. Based on amplicon sequencing, the bacterial communities were dominated by the phyla Pseudomonadota and Bacteroidota, while the most abundant archaea belonged to the phyla Nitrososphaerota and Nanoarchaeota. The changing environmental factors had an effect on the composition of the epilithic microbial community. Critical levels of faecal pollution in the water were associated with increased relative abundance of Sphaerotilus , a typical indicator of “sewage fungus”, but the composition and diversity of the epilithic biofilms were also influenced by several other environmental factors such as temperature, water discharge and total suspended solids (TSS). The specific PCRs showed opportunistic pathogenic bacteria (e.g. Pseudomonas spp., Legionella spp., P. aeruginosa , L. pneumophila , Stenotrophomonas maltophilia ) in some biofilm samples, but extended spectrum β -lactamase (ESBL) genes and macrolide resistance genes could not be detected.
... Total suspended solids and inorganic particulate matter were determined during the annual cycle according to Eiler et al. (2003). ...
... The hypertrophic shallow soda lake (Oberer Stinker, OS) is characterized by high total salt concentrations and turbidity (Eiler et al., 2003;Kirschner et al., 2004). It was formed by mineral solutes ascending with the groundwater flux (Krachler et al., 2000) and is characterized by pH values ranging from 9.4 to 10 (Eiler et al., 2003). ...
... The hypertrophic shallow soda lake (Oberer Stinker, OS) is characterized by high total salt concentrations and turbidity (Eiler et al., 2003;Kirschner et al., 2004). It was formed by mineral solutes ascending with the groundwater flux (Krachler et al., 2000) and is characterized by pH values ranging from 9.4 to 10 (Eiler et al., 2003). Na + is the dominating cation, and HCO 3 − , CO 3 2− , Cl − , and SO 4 2− represent the major anions. ...
... Na + is the dominating cation, and HCO 3 − , CO 3 2− , Cl − , and SO 4 2− represent the major anions. Salinity of the soda lake varies strongly with seasons (Eiler et al., 2003). ...
Molecular diagnostic methods are increasingly applied for food and environmental analysis. Since several steps are involved in sample processing which can affect the outcome (e.g., adhesion of DNA to the sample matrix, inefficient precipitation of DNA, pipetting errors and (partial) loss of the DNA pellet during DNA isolation), quality control is essential at all processing levels. In soil microbiology, particular attention has been paid to the inorganic component of the sample matrix affecting DNA extractability. In water quality testing, however, this aspect has mostly been neglected so far, although it is conceivable that these mechanisms have a similar impact. The present study was therefore dedicated to investigate possible matrix effects on results of water quality analysis. Field testing in an aquatic environment with pronounced chemo-physical gradients [total suspended solids (TSS), inorganic turbidity, total organic carbon (TOC), and conductivity] indicated a negative association between DNA extractability (using a standard phenol/chloroform extraction procedure) and turbidity (spearman ρ = −0.72, p < 0.001, n = 21). Further detailed laboratory experiments on sediment suspensions confirmed the hypothesis of inorganic turbidity being the main driver for reduced DNA extractability. The observed effects, as known from soil samples, were also indicated to result from competitive effects for free charges on clay minerals, leading to adsorption of DNA to these inorganic particles. A protocol modification by supplementing the extraction buffer with salmon sperm DNA, to coat charged surfaces prior to cell lysis, was then applied on environmental water samples and compared to the standard protocol. At sites characterized by high inorganic turbidity, DNA extractability was significantly improved or made possible in the first place by applying the adapted protocol. This became apparent from intestinal enterococci and microbial source tracking (MST)-marker levels measured by quantitative polymerase chain reaction (qPCR) (100 to 10,000-fold median increase in target concentrations). The present study emphasizes the need to consider inorganic turbidity as a potential loss factor in DNA extraction from water-matrices. Negligence of these effects can lead to a massive bias, by up to several orders of magnitude, in the results of molecular MST and fecal pollution diagnostics.
... To determine the influence of the elements' composition on the distribution of SRB strains, cluster analysis by the PCA method was performed. This method is widely used for the analysis of multidimensional systems in biology, physics, medicine, etc. [44,45,48,49]. ...
... In the work by Eiler (2003) [48], five diluted soda lakes in eastern Austria and factors of abundance of heterotrophic bacteria, their production, and their controlling factors were investigated. In these ecosystems, the environmental factors, which are responsible for the control of the microbial community in the shallow soda pools, were investigated during an annual cycle. ...
... In the work by Eiler (2003) [48], five diluted soda lakes in eastern Austria and factors of abundance of heterotrophic bacteria, their production, and their controlling factors were investigated. In these ecosystems, the environmental factors, which are responsible for the control of the microbial community in the shallow soda pools, were investigated during an annual cycle. ...
The monitoring of trace metals in microbial cells is relevant for diagnosis of inflammatory bowel disease (IBD). Sulfate-reducing bacteria (SRB) represent an important factor in the IBD development. The content of trace metals in bacterial cells may reflect the functioning of the enzyme systems and the environmental impact on the occurrence of SRB. The aim of our research was to compare the content of trace elements in the cells of SRB cultures isolated from fecal samples of patients with IBD and healthy people. The contents of 11 chemical elements in the bacterial cells of SRB were analyzed by the inductively coupled plasma-mass-spectrometry (ICP-MS) method. Significant changes in the content of calcium, zinc, magnesium, potassium, and iron were observed in patients with IBD compared to healthy individuals. Through a principal component analysis (PCA), a total variability of 67.3% in the difference between the samples was explained. The main factors influencing the total variability in the bacterial cells of SRB isolated from patients suffering from IBD were the content of the micro- and trace elements, such as manganese (with power 0.87), magnesium and cobalt (0.86), calcium (0.84), molybdenum (0.81), and iron (0.78). Such changes in the elemental composition of SRB under different conditions of existence in the host may indicate adaptive responses of the microorganisms, including the inclusion of oxidative stress systems, which can lead to changes in SRB metabolism and the manifestation of parameters of IBD in humans. The use of PCA might make it possible in the future to predict the development and ratio of SRB in patients with various diseases.
... The environmental variables measured reflected multiple extreme conditions and were similar to those that had previously been reported in soda pans of the Carpathian Basin 2,3 ; i.e. the turbid Zab-szék pan had a higher average concentration of ISS (1436 mg l −1 ) than the colored Sós-ér pan (86 mg l −1 ), while DOC values where higher in the latter (75 mg l −1 vs. 490 mg l −1 , respectively), pH was alkaline (~ 9-10) and the salinity ranged between 1.5 to 18.9 g l −1 (subsaline to hyposaline, according to Hammer 17 ). Prokaryotic cell numbers were in the same magnitude as had been measured previously in the soda pans of the region studied (10 6 -10 8 cells ml −1 ) 22 , but higher than in five soda pans from the Seewinkel region (Austria) (10 6 cells ml −1 ) 23 . Interestingly, the number of cells did not increase linearly with the depth of the pans, indicating the dynamic nature of the prokaryotic community and the ecosystem. ...
... Members of the acI clade, another small cellsized planktonic Actinobacteria, are capable of utilizing N-acetylglucosamine (monomeric unit of chitin and component of the bacterial murein cell-wall) 10,46,47 , which can also contribute to the increase of their relative abundance with zooplankton numbers. In previous works on soda pans of the Seewinkel region 23,48 , the authors stated that the observed high abundance of cladocerans (2 × 10 3 specimen l −1 ) and protists must be an important regulatory factor on the bacterial population. In conclusion, intensive grazing by zooplankton could favor planktonic Actinobacteria by the elimination of their larger, fast-growing bacterial competitors and also by their ability to degrade chitin, which could present in high amounts in the water by the end of the zooplankton 'bloom' . ...
Astatic soda pans of the Pannonian Steppe are unique environments with respect to their multiple extreme physical and chemical characteristics (high daily water temperature fluctuation, high turbidity, alkaline pH, salinity, polyhumic organic carbon concentration, hypertrophic state and special ionic composition). However, little is known about the seasonal dynamics of the bacterial communities inhabiting these lakes and the role of environmental factors that have the main impact on their structure. Therefore, two soda pans were sampled monthly between April 2013 and July 2014 to reveal changes in the planktonic community. By late spring in both years, a sudden shift in the community structure was observed, the previous algae-associated bacterial communities had collapsed, resulting the highest ratio of Actinobacteria within the bacterioplankton (89%, with the dominance of acIII-A1 lineage) ever reported in the literature. Before these peaks, an extremely high abundance (> 10,000 individuum l⁻¹) of microcrustaceans (Moina brachiata and Arctodiaptomus spinosus) was observed. OTU-based statistical approaches showed that in addition to algal blooms and water-level fluctuations, zooplankton densities had the strongest effect on the composition of bacterial communities. In these extreme environments, this implies a surprisingly strong, community-shaping top-down role of microcrustacean grazers.
... The abundance of planktonic bacteria is around 10 6 -10 7 cells/mL and 10 7 -10 8 cells/mL in the soda lakes and pans, respectively (Eiler et al. 2003;Kirschner et al. 2002;Szabó et al. 2020;Szabó-Tugyi et al. 2019;Vörös et al. 2008), and they belong mainly to the phyla Actinobacteria, Bacteroidetes and Proteobacteria (Bell et al. 2018;Bullerjahn et al. 2020;Szabó et al. 2017Szabó et al. , 2020Fig. 3). ...
... Remarkable diel changes in the planktonic microbial activity and abundance were also observed in the shallow soda pans, and external abiotic factors (diluting the effect of rainfall which decreases salinity, but also the grazing pressure and viral lysis, the wind-induced sediment resuspension, and daily fluctuations of temperature and irradiation) seem to have a regulating effect on them (Kirschner et al. 2002;Krammer et al. 2008). The generation time of bacteria in these environments can be as little as a few hours (Eiler et al. 2003;Krammer et al. 2008). Growth studies on planktonic bacterial isolates have shown that the type of dominant anion determines the adaptation of prokaryotes, since strains isolated from soda pans grew better in media containing (hydrogen) carbonate than in media containing the same amount of chloride (Bedics et al. 2019). ...
In this review, I would like to summarize the current knowledge on the microbiology of soda lakes and pans of the Carpathian Basin. First, the characteristic physical and chemical features of these sites are described. Most of the microbiological information presented deals with prokaryotes and algae, but protists and viruses are also mentioned. Planktonic bacterial communities are dominated by members of the phyla Actinobacteria, Bacteroidetes and Proteobacteria; small-sized trebouxiophycean green algae and Synechococcus/Cyanobium picocyanobacteria are the most important components of phytoplankton. Based on the current knowledge, it seems that mainly temperature, salinity, turbidity and grazing pressure regulate community composition and the abundance of individual microbial groups, but the external nutrient load from birds also has a significant impact on the ecological processes.
... As suspended inorganic particles (e.g. clay, silt; Eiler et al., 2003) interfere with the filter-feeding process (Kirk & Gilbert, 1990), their high concentration in the water is expected to have a negative effect on zooplankters (Dejen, Vijverberg, Nagelkerke, & Sibbing, 2004;Teffera et al., 2018;Zhou, Qin, & Han, 2018). There is, however, a difference among suspension feeders in their ability of coping with (often extreme) turbid conditions. ...
1. Omnivory is widespread in food webs, with an important stabilising effect. The strength of omnivorous trophic interactions may change considerably with changes in the local environment.
2. Shallow temporary waters are often characterized by high levels of inorganic turbidity that may directly limit the food uptake of filter-feeding organisms, but there is little evidence on how it might affect omnivorous species. Anostracans are key species of temporary waters and recent evidence suggests that these organisms are omnivorous consumers of both phyto-and zooplankton.
3. Using Branchinecta orientalis as a model species, our aim was to test how turbidity affects the feeding of an omnivorous anostracan. To do this, we used short-term feeding experiments and stable isotope analyses, with animals collected from soda pans in eastern Austria. In the feeding experiments, algae and zooplankton were offered as food either separately or in combination. The prey type treatments were crossed with turbidity levels in a factorial design.
4. There was a pronounced decrease in the ingested algal biomass with increasing turbidity. Conversely, ingestion rates on zooplankton were less affected by turbidity. Stable isotope analyses from field material supported our experimental results by showing a positive relationship of the trophic position of anostracans and the trophic niche of the communities with turbidity.
5. Our results show that turbidity modulates the intraguild trophic relationship between anostracans and their prey by shifting the diet of anostracans from more herbivorous in transparent to more carnivorous in turbid waters. Thus, inorganic turbidity might also have a community shaping role in plankton communities of temporary waters through altering trophic relationships.
... Two main types of these shallow lakes (which are usually referred as pans) could be distinguished, the 'turbid type' (high amount of suspended solids and usually high concentration of humic substances) and the 'colored type' (relatively low amount of suspended solids and very high concentration of humic substances) (Boros et al. 2017). The 'fluid sediment' concept has been proposed for the turbid water type, as wind induces continuous sediment resuspension due to their extreme shallowness (< 50 cm) (Eiler et al. 2003;Boros et al. 2017). ...
... As these habitats are turbid due to wind-induced mixing and groundwater upwelling (Boros et al. 2017) which provide competitive advantage to picoalgae , we assume that besides calm weather, other factors (e.g. other meteorological and hydromorphological conditions, geographical position, selective zooplankton grazing; Eiler et al. 2003;Horváth et al. 2014) had contributed to the development of the Oocystis bloom. Contrary to many saline lakes (e.g. ...
In April 2014, dual bloom of green algae and purple bacteria occurred in a shallow, alkaline soda pan (Kiskunság National Park, Hungary). The water was only 5 cm deep, in which an upper green layer was clearly separated from a near-sediment purple one. Based on microscopy and DNA-based identification, the upper was inhabited by a dense population of the planktonic green alga, Oocystis submarina Lagerheim, while the deeper layer was formed by purple, bacteriochlorophyll-containing bacteria, predominated by Thiorhodospira and Rhodobaca. Additional bacterial taxa with a presumed capability of anoxygenic phototrophic growth belonged to the genera Loktanella and Porphyrobacter. Comparing the bacterial community of the purple layer with a former blooming event in a nearby soda pan, similar functional but different taxonomic composition was revealed. Members from many dominant bacterial groups were successfully cultivated including potentially new species, which could be the result of the application of newly designed media.
... Two of them, Zicklacke (ZL) and Unterstinker (US), were selected as additional sampling sites. These soda pools are characterized by very high pH values, up to 9.9, very high inorganic and organic nutrient concentrations and chlorophyll a values (Table 1), an extremely active microbial community (30,31), high turbidity, and thus an extremely challenging water matrix. ...
... The annual course of the 250 nm/365 nm absorbance ratios in the pools was opposite to that of the ratios in the lake. While refractory material in the lake from the reed stand mainly fuels the DOC pool in summer (32), benthic and pelagic algae releasing low-molecular-weight substances mainly fuel the DOC pool in the soda pools (30). Thus, we propose that in the soda pools, the negative effect of the high-molecular-weight substances on the GR rates (36) (positive correlation with 250 nm/365 nm absorbance ratios) is masked by the specific ecological conditions in the soda pools (high percentage of low-molecularweight substances present in summer, when GR rates are low due to temperatureinduced effects on the presence of DNA binding particles). ...
... Conductivity (LF330; WTW, Germany), water temperature, pH (GHM, Seibold Vienna, Austria), oxygen concentration (OXI 330i; WTW), and Secchi depth were measured in situ. Additionally, 1 liter of water was collected in a clean plastic bottle to analyze inorganic nutrients, chlorophyll a, total suspended solids (TSS), and DOC, and the spectrophotometric absorption ratio was measured at 250 nm and 365 nm according to the methods described by Eiler et al. (30) and Kirschner et al. (27). ...
In recent years, global warming has led to a growing number of Vibrio cholerae infections in bathing water users in regions formerly unaffected by this pathogen. It is therefore of high importance to monitor V. cholerae in aquatic environments and to elucidate the main factors governing its prevalence and abundance. For this purpose, rapid and standardizable methods that can be performed by routine water laboratories are prerequisite. In this study, we applied a recently developed multiplex quantitative PCR (qPCR) strategy (i) to monitor the spatiotemporal variability of V. cholerae abundance in two small soda pools and a large lake that is intensively used for recreation and (ii) to elucidate the main factors driving V. cholerae dynamics in these environments. V. cholerae was detected with qPCR at high concentrations of up to 970,000 genomic units 100 ml⁻¹ during the warm season, up to 2 orders of magnitude higher than values obtained by cultivation. An independent cytometric approach led to results comparable to qPCR data but with significantly more positive samples due to problems with DNA recovery for qPCR. Not a single sample was positive for toxigenic V. cholerae, indicating that only nontoxigenic V. cholerae (NTVC) was present. Temperature was the main predictor of NTVC abundance, but the quality and quantity of dissolved organic matter were also important environmental correlates. Based on this study, we recommend using the developed qPCR strategy for quantification of toxigenic and nontoxigenic V. cholerae in bathing waters with the need for improvements in DNA recovery.
... Other important questions relate to the potential impact of the microbiota on the "self-purification" of spring water quality and on carbonate geochemistry (Gray & Engel, 2013). In this respect, prokaryotic activity measurements performed in NCA spring water from DKAS1 and LKAS2 based on sensitive analytical isotope approaches revealed extremely low heterotrophic production rates (i.e., 0.72 to 82 pg carbon L −1 hr −1 for DKAS1, and 6 to 900 pg carbon L −1 hr −1 for LKAS2) during two annual cycles of investigation ); these measured production rates were among the lowest values ever measured for aquatic habitats (Eiler et al., 2003;Laybourn-Parry, Quayle, Henshaw, Ruddell, & Marchant, 2001). The combination of activity measurements, microscopy, and specific cell-labeling techniques (i.e., catalyzed reporter deposition-FISH-microautoradiography) further demonstrated that, on average, only 7% (range 3-14%) of the observed TCC in the spring water were active, with very long generation times of up to 684 days ). ...
Over the past 15 years, pioneering interdisciplinary research has been performed on the microbiology of hydrogeologically well‐defined alpine karst springs located in the Northern Calcareous Alps (NCA) of Austria. This article gives an overview on these activities and links them to other relevant research. Results from the NCA springs and comparable sites revealed that spring water harbors abundant natural microbial communities even in aquifers with high water residence times and the absence of immediate surface influence. Apparently, hydrogeology has a strong impact on the concentration and size of the observed microbes, and total cell counts (TCC) were suggested as a useful means for spring type classification. Measurement of microbial activities at the NCA springs revealed extremely low microbial growth rates in the base flow component of the studied spring waters and indicated the importance of biofilm‐associated microbial activities in sediments and on rock surfaces. Based on genetic analysis, the autochthonous microbial endokarst community (AMEC) versus transient microbial endokarst community (TMEC) concept was proposed for the NCA springs, and further details within this overview article are given to prompt its future evaluation. In this regard, it is well known that during high‐discharge situations, surface‐associated microbes and nutrients such as from soil habitats or human settlements—potentially containing fecal‐associated pathogens as the most critical water‐quality hazard—may be rapidly flushed into vulnerable karst aquifers. In this context, a framework for the comprehensive analysis of microbial pollution has been proposed for the NCA springs to support the sustainable management of drinking water safety in accordance with recent World Health Organization guidelines. Near‐real‐time online water quality monitoring, microbial source tracking (MST) and MST‐guided quantitative microbial‐risk assessment (QMRA) are examples of the proposed analytical tools. In this context, this overview article also provides a short introduction to recently emerging methodologies in microbiological diagnostics to support reading for the practitioner. Finally, the article highlights future research and development needs.
This article is categorized under: 1Engineering Water > Water, Health, and Sanitation
2Science of Water > Water Extremes
3Water and Life > Nature of Freshwater Ecosystems