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Introduction: Inland navigation has seen explosive growth over the past few decades, leading to increasing concerns about its environmental and health impacts. Coastal waters are usually monitored for wastewater contamination by maritime traffic, but little is known about faecal pollution caused by the inland waterways transport in large rivers. The Danube River in Europe is a very popular destination for cruise ship trips. The extent to which the faecal pollution in the Danube is caused by shipping traffic in general and the growing number of cruise ships specifically is still largely unknown. The Danube River Information Service (DoRIS) has been established to track ship traffic and provide data for monitoring in Austria. This database allows the estimation of the faecal pollution potential of ships with a high level of spatial and temporal resolution for the first time.Methodology: An approach was developed to investigate the potential contribution of various ship categories to faecal pollution in the Danube River (Lower Austria) by combining water quality monitoring data with ship traffic data. The ship traffic data was extracted from DoRIS using a Python-based programming language code and sorted into three categories (cruise, passenger, and freight ships). Water quality monitoring was conducted at 11 transects along a 223-kilometre Danube River reach in Lower Austria. In collaboration with local authorities, each river transect was sampled at 5 points across the profile for one year at monthly intervals. The faecal indicator bacterium E. coli along with physio-chemical water quality parameters was analyzed for all samples. Theoretical faecal impact scenarios were developed using data on average daily ship traffic and factors such as ship type, onboard wastewater treatment facilities, onboard passenger capacity, and seasonal fluctuations of cruise tourism. To evaluate the influence of local and regional shipping traffic on the faecal pollution dynamics, a statistical correlation analysis was performed using data from the entire river reach and ship berthing stations.Results: The faecal impact scenario analysis, revealed that the shipping industry had the same degree of maximum pollution potential as treated municipal wastewater. In case of improper onboard wastewater treatment, faecal pollution can be substantial. According to water quality monitoring, 94% of the samples had low to moderate faecal pollution, while none were classified as high. As a result, no significant increase in E. coli concentrations was detected throughout the 223 km long river stretch. However, at one of the 11 river transects, significant variations in the E. coli concentration were detected. After conducting a correlation analysis using statistical parameters for the whole river reach, we found no significant correlation between E. coli concentrations and any of the investigated ship counting metrics or ship types. Nonetheless, E. coli concentration was found to be significantly higher at one of the cruise ship berthing stations.Acknowledgement: The research was funded by Amt der Niederösterreichischen Landesregierung, Abteilung Wasserwirtschaft (WA2) and the GFF Niederösterreich mbH (LS19-016 Future Danube). We would like to thank collaboration partners from the government of Lower Austria and the Austrian shipping inspectorate.

We developed an innovative approach to estimate the extent of fecal pollution sources for urban river catchments. The methodology consists of 1) catchment surveys complemented by literature data where needed for probabilistic estimates of daily produced fecal indicator (FIBs, E. coli, enterococci) and zoonotic reference pathogen numbers (Campylobacter, Cryptosporidium and Giardia) excreted by human and animal sources in a river catchment, 2) generating a hypothesis about the dominant sources of fecal pollution and selecting a source targeted monitoring design, and 3) verifying the results by comparing measured concentrations of chemical tracers, C. perfringens, and host-associated genetic microbial source tracking (MST) markers in the river, and by multi-parametric correlation analysis. We tested the approach at a study area in Vienna, Austria. The daily produced microbial particle numbers according to the probabilistic estimates indicated that, for the dry weather scenario, the discharge of treated wastewater (WWTP) was the primary contributor to fecal pollution. For the wet weather scenario, 80-99 % of the daily produced FIBs and pathogens resulted from combined sewer overflows (CSOs) according to the probabilistic estimates. When testing our hypothesis in the river, the measured concentrations of the human genetic fecal marker were log10 4 higher than for selected animal genetic fecal markers. Our analyses showed for the first-time statistical relationships between C. perfringens and a human genetic fecal marker (i.e. HF183/BacR287) with the reference pathogen Giardia in river water (Spearman rank correlation: 0.78-0.83, p

Groundwater contamination and transport of viruses and bacteria in aquifers are a major concern worldwide. To ascertain the ability of these aquifers to remove pathogens, tracer tests with microbial surrogates are carried out. These tests are laborious and may require special permits, and therefore, column tests are often done instead. Unfortunately, results from column tests tend to grossly overestimate removal rates when compared to the field scale, which can lead to an underestimation of groundwater contamination risks. Scale is an important consideration when examining pathogen transport through porous media, as pathogen removal is rarely a linear process. In this study, field tests were carried out with endospores of Bacillus subtilis and coliphage phiX174 over a distance of 25 m in an alluvial gravel aquifer near Vienna, Austria. The sandy gravel material from the field site was also used in column tests with the same tracers. Both attachment-detachment and colloid filtration theory were used to model these tests, as well as log-removal rates per meter. The results show that the spatial removal rate (log/m) is approximately 2 orders of magnitude higher on the column scale, when compared to the field. A comparison with the literature showed a correlation between the heterogeneity of the porous media and the difference in removal rates between the column and field scale., Tracer tests at different scales showed that preferential flow is an important factor affecting upscaling of microbial transport.

The current fecal indicator concept is based on the assumption that the standard fecal indicator bacteria (SFIB) Escherichia coli, intestinal enterococci, and Clostridium perfringens multiply significantly only in the guts of humans and other homeothermic animals and can therefore indicate fecal pollution and the potential presence of pathogens from those groups. The findings of the present study showed that SFIB can also occur in high concentrations in poikilothermic animals (i.e., animals with body temperatures that vary with the ambient environmental temperature, such as fish, frogs, and snails) in an alluvial backwater area in a temperate region, indicating that a reconsideration of this long-standing indicator paradigm is needed. This study suggests that poikilotherms must be considered to be potential primary sources of SFIB in future studies.

The transport of human adenovirus, nanoparticles, and PRD1 and MS2 bacteriophages was tested in fine granular limestone aquifer material taken from a borehole at a managed aquifer recharge site in Adelaide, South Australia. Comparison of transport and removal of virus surrogates with the pathogenic virus is necessary to understand the differences between the virus and surrogate. Because experiments using pathogenic viruses cannot be done in the field, laboratory tests using flow-through soil columns were used. Results show that PRD1 is the most appropriate surrogate for adenovirus in an aquifer dominated by calcite material but not under high ionic strength or high pH conditions. It was also found that straining due to size and the charge of the colloid were not dominant removal mechanisms in this system. Implications of this study indicate that a certain surrogate may not represent a specific pathogen solely based on similar size, morphology, and/or surface charge. Moreover, if a particular surrogate is representative of a pathogen in one aquifer system, it may not be the most appropriate surrogate in another porous media system. This was apparent in the inferior performance of MS2 as a surrogate, which is commonly used in virus transport studies.

The bacterioplankton diversity in large rivers has thus far been undersampled, despite the importance of streams and rivers as components of continental landscapes. Here, we present a comprehensive dataset detailing the bacterioplankton diversity along a midstream transect of the Danube River and its tributaries. Using 16S rRNA-gene amplicon sequencing, our analysis revealed that bacterial richness and evenness gradually declined downriver in both the free-living and particle-associated bacterial communities. These shifts were also supported by the beta diversity analysis, where the effects of tributaries were negligible in regards to the overall variation. In addition, the river was largely dominated by bacteria that are commonly observed in freshwater and typical of lakes, whereas only few taxa attributed to lotic systems were detected. These freshwater taxa, which were composed of members of the acI lineage and the freshwater SAR11 group (LD12) and the Polynucleobacter, increased in proportion downriver and were accompanied by a decrease in soil and groundwater bacteria. When examining our results in a broader ecological context, we elaborate that patterns of bacterioplankton diversity in large rivers can be explained by the River Continuum Concept published in 1980, with a modification for planktonic microorganisms. (version 2.0 submitted to Environmental Microbiology 2014-Sept-09)