Environmental history of one of the largest freshwater neotropical fish (Zungaro jahu) from otolith isotopic analysis

The Manguruyú Zungaro jahu, endemic to the La Plata Basin, is one of the largest neotropical fish species whose life history is virtually unknown. The objectives of this study were to determine if Z. jahu is a large-scale migratory species and to describe habitat use throughout ontogeny using the otolith Sr isotope (⁸⁷Sr/⁸⁶Sr) ratio. Surface water samples were collected in 2020 at four sites representing the main water courses of the Great Pantanal in Brazil (upper Paraguay, Cuiabá, São Lourenço and Vermelho rivers). Eighteen fish individuals were collected from the Paraná River (Argentina). New water ⁸⁷Sr/⁸⁶Sr data were incorporated into previously established statistical models to infer the fish habitat use through the otolith ⁸⁷Sr/⁸⁶Sr ratios. The water ⁸⁷Sr/⁸⁶Sr ratio of the upper Paraguay tributaries varied (0.7209 and 0.7229) and were the highest in the La Plata Basin. The dispersal area of Z. jahu was restricted to the surroundings of the confluence of the Paraná and Paraguay rivers. Fish showed chemical signatures compatible with those of the middle Paraná (88%), Paraguay-Pilcomayo-Bermejo (50%) and the lower/upper Paraná (66%). The discriminant analysis based on otolith core indicated natal origins from the middle Paraná (37%), upper Paraná (32%), and Paraguay sub-basin (32%). The dispersal area of Z. jahu migrations could be restricted to the surroundings of the confluence of Paraná and Paraguay, which highlights the need to review regional fishing regulations, especially between latitudes 30°–34° S.     

Estimating contributions from nursery areas to fish stocks in freshwater systems using otolith fingerprints: The case of the streaked prochilod in the La Plata Basin (South America)

Stock composition studies using otolith fingerprints have scarcely been developed in freshwater systems. In this context, the La Plata Basin is the second largest fluvial‐marine system of South America, where Prochilodus lineatus is the most important fishery resource. Despite the basin importance, estimation of mixed stock composition has not been explored yet. In this paper, the contribution of the two main nursery areas to two fishing stocks (Uruguay and Paraná rivers) of P. lineatus was evaluated using otolith's core microchemistry, considering two groups: subadult (2 years) and adult (4 years). Estimates were made using two maximum likelihood methods. Chemical composition of young‐of‐year fish caught in nursery areas in 2010 was used as baseline of the models, whereas chemical composition of the core of subadult and adult otoliths was used as sample of unknown origin. Results suggest that the subadult stock from Paraná was not mixed (contribution ~ 100%), whereas the stock from Uruguay had a contribution from the Paraná nursery (1.5 ± 1.2–17.9 ± 3.96%). For the adults, the degree of mixing increased and the contribution from both nursery areas to the Paraná and Uruguay stocks varied between 14.8 ± 4.18% and 85.2 ± 4.18%, respectively. The potential application of otolith fingerprints and maximum likelihood mixture models is here highlighted for determining the relative importance of recruitment sources of fish in the La Plata Basin. Because the contributions of the different nursery areas shared among several nations in turn affect the composition of internationally shared stocks, comprehensive management agreements at the basin level are necessary.     

Occurrence of Alternative Fecal Indicators and Enteric Viruses in Michigan Rivers

Fecal contamination has been a leading problem associated with the impairment of surface waters in the State of Michigan. However, the source of the contamination and the possible presence of pathogens has not been adequately addressed. In this preliminary study, nine major rivers located in the Lower Peninsula of Michigan were investigated for the presence of fecal coliforms, Escherichia coli, enterococci, coliphage, and enteric viruses. Five sites (56%) exceeded the allowable limits set for recreational waters based on E. coli concentrations for the State of Michigan. Three (33%) of these sites (Grand, Kalamazoo, and Rouge rivers) tested positive for the presence of viable enteric viruses. The presence of enteric viruses and elevated levels of microbial indicators suggest that these waters may pose a threat to the health of individuals using them for recreational activities.Several new genotypic and phenotypic characterization methods have emerged that have the ability to define human and animal sources of fecal indicators. Previously, we developed a host-associated molecular marker for Enterococcus faecium, which is human specific and targets the sequence for the enterococcal surface protein (esp). When the nine rivers were screened for the marker, two (Grand and Rouge rivers) were found to be positive, implying the presence of human fecal contamination. This study suggests a preliminary approach for validating the use of molecular markers for identifying sources of fecal pollution in the Great Lakes Region and the human health risks associated with pathogenic viruses.     

Trends in health risks from water-related diseases and cyanotoxins in Ugandan portion of Lake Victoria basin

Studies to examine the prevalence of water‐related diseases, cyanobacteria toxins and other health risks at landing beaches in the Ugandan portion of the Lake Victoria basin were carried out. Based on surveillance studies and other data sources in the region, water samples were analysed for indications of faecal contamination. The coliform numbers were generally high for most sampling sites, indicating significant water contamination. The wet seasons exhibited significantly higher coliform counts than the dry seasons for all lakeshore sample sites. This seasonal variation in coliform counts correlated positively with the incidence of waterborne diseases, which are typically higher in the wet season. The water supply for domestic consumption for the Lake Victoria riparian communities is mainly the lake itself. The most prevalent diseases associated with the landing sites include malaria, dysentery, diarrhoea and bilharzia. Malaria was most prevalent, followed by dysentery, in all the studied districts. Many people in the catchment dispose of faecal wastes in lakeshore area bushes, or in polythene bags, contaminating water sources with faecal material, and resulting in waterborne diseases. The vulnerability of lakeside communities to water‐related diseases is further aggravated by low accessibility to health facilities and personnel. Further, cyanobacteria (potentially toxic to humans and animals) dominate other algal species in Lake Victoria, contributing >50% of the algal biomass. Algal blooms occurred frequently in Murchison Bay, a source of drinking water for the city of Kampala and surrounding urban centres. Algal blooms can cause unpleasant odours and tastes in domestic water supplies, clog pump and machinery filters, increase chlorine demands for water disinfection, and necessitate more complex and expensive treatment processes. The findings of this study suggest improved water quality, changes in sanitation and hygiene behaviour could significantly reduce the prevalence of water‐related diseases and cyanotoxins in the Ugandan portion of the Lake Victoria basin.     

Microbial quality of water in Barekese reservoir and feeder streams in Ghana

Concern is growing in Ghana about the high incidence of water‐related diseases and deaths resulting from use of water contaminated with microorganisms. This water often remains unsafe for human consumption because of inadequate decontamination of microbially infected water. Data are presented in this study on the microbial quality of Barekese reservoir, which is the main drinking water reservoir for the city of Kumasi and its environs (population = 2, 5 million), and nine feeder streams in its catchment. Water samples were collected from 13 sampling sites and analysed for Escherichia coli, total and faecal coliforms. Furthermore, 18 faecal coliform isolates were randomly selected from all sampling sites and confirmed as E. coli using Analytical Profile Index 20E system. Escherichia coli, total and faecal coliforms were enumerated using the most probable number method. Mean bacterial indicator numbers from all sampling sites ranged from 1.45 × 10⁴ to 9.50 × 10⁷ 100 mL^?1 for total coliforms, 1.60 × 10³ to 9.00 × 10⁵ 100 mL^?1 for faecal coliforms and 1.50 × 10¹ to 9.50 × 10³ 100 mL^?1 for E. coli. Indicator numbers exceeded the World Health Organization (0.100 mL^?1) for E. coli and Ghana Water Resources Commission‐Target Water Quality Range of 5–100 100 mL^?1 for total coliforms and 0.100 mL^?1 for faecal coliforms in water used for domestic purposes. The identified isolates in Barekese Reservoir and its feeder streams belonged to Serratia, Enterobacter, Citrobacter, Salmonella and Klebsiella genera. Bacterial numbers were significantly (P < 0.05) higher in the feeder streams, compared with Barekese Reservoir water. This finding indicates the feeder streams pose health risks to local communities that withdraw water from them. The results of this study highlight the urgent need to raise public awareness on the adverse effects of water‐quality degradation through improper waste disposal methods in order to decrease the cost of treating the reservoir water.     

Microbial pollution characterization at a TMDL site in Michigan: Source identification

Communities throughout the Great Lakes basin are developing and implementing watershed management plans to address non-point sources of pollution and meet Total Maximum Daily Load (TMDL) requirements. Investigating sources of microbial contamination in key streams and creeks is critical for the development of effective watershed management plans. This work aims to present an approach that will facilitate source identification. In addition to conventional indicator analysis, the approach includes molecular analysis of species-specific markers and microbial community diversity analysis. We characterized microbial pollution in the Sloan Creek subwatershed in Ingham County MI, an impaired area, located in the Great Lakes Basin. To identify pollution sources (human or animal) and major sites of origin (tributaries with highest pollution loads) water samples were collected from three locations in the subwatershed representing the main creek upstream, main creek downstream, and tributary. A fecal indicator (E. coli) and host-specific human and bovine-associated Bacteroides genetic markers were quantified in all water samples. Results indicated that 54% of the samples from the three locations exceeded the recreational E.coli water quality guidelines. High concentrations of both human and bovine associated-Bacteroides indicated influence of multiple sources of fecal contamination. Statistical tests showed significantly different water characteristics between two of the sampling locations. Whole genome shotgun sequencing indicated fecal and sewer signatures, wastewater metagenome, human gut metagenome, and rumen gut metagenome in the water samples. Results suggested that probable sources of contamination were leakage from septic systems and runoff from agriculture activities nearby to Sloan Creek.     

Enrichment and geoaccumulation of metals in the superficial sediments of Lake Chivero,Zimbabwe

Sediments act as a sink, being an integrator and an amplifier for metals in rivers, lakes and reservoirs. Thus, sediment quality has been recognized as an important indicator of aquatic pollution. The concentrations of aluminium (Al), calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn) and sodium (Na) were studied in the surface sediments of Lake Chivero, Zimbabwe, to determine metal accumulation, distribution, pollution status and to distinguish natural background metal levels from human pollution sources. Sediment samples were collected from 17 locations during a two‐year (2014–2015) monitoring period during the hot–dry, hot–wet and cool–dry seasons. The overall mean metal concentrations exhibited the following decreasing order: Fe > Al>Mn > Ca>K > Mg>Na. The Mn levels for all sites and seasons were above the severe effect level (SEL). The highest metal and enrichment factor (EF) values were observed for the hot–wet season, indicating the period when the reservoir received the highest metal pollution from its catchment. The Geochemical index (I_geo) values for Mn for all seasons indicated moderately to strong contamination in sediments. The pollution load index (PLI) for all seasons indicated low pollution levels. Sediment contamination was attributed to natural sources for Al, Na and K and anthropogenic sources for Fe, Ca, Mg and Mn. The levels of studied metals in the Lake Chivero sediments are comparable to other eutrophic lentic systems. The results of the present study provide baseline information necessary for developing future metal pollution control strategies for Lake Chivero and its catchment.     

Using a weight-of-evidence approach for management of watersheds.

This research used a weight-of-evidence approach to evaluate sources of contaminants in a drinking water watershed that serves as part of the City of Boston's water supply. The approach incorporated land use analysis using GIS, sanitary surveys, traditional water quality monitoring and microbial source tracking (MST) tools. Case-study tributaries were selected based on elevated faecal coliform counts. Land use analysis and sanitary surveys were used to identify suspected microbial sources, including residential septic systems, agricultural animal operations, commercial/industrial operations and wildlife activity. Sampling sites were selected to hydrologically isolate potential contamination sources. Samples were collected seasonally over 1 year and analysed for traditional and MST parameters. Results demonstrated that both septic systems and a horse stable were contributing microbial loads in the first tributary. In the second tributary, septic systems from the townhouses were contributing microbial loads while a plant nursery was contributing organic matter. This evidence was used to evaluate best management practices to mitigate the contamination.     

Bacteroides spp. as reliable marker of sewage contamination in Hawaii's environmental waters using molecular techniques.

Standard PCR (SPCR) and quantitative PCR (QPCR) assays using primers for general and for human-specific Bacteroides 16S rRNA markers were selected as the molecular tests to assess sewage contamination in recreational waters of Hawaii and these same water samples were assayed for culturable concentrations of selected faecal microbial indicators. The results of this study showed that the general primer for Bacteroides was not useful because ambient and polluted water samples were positive for this marker. However, use of human-specific primers reliably detected sewage contamination. The human-specific Bacteroides detection data supported previously reported conclusions that concentrations of alternative faecal indicators (C. perfringens, FRNA coliphages) but not traditional faecal indicators (faecal coliform, E. coli, enterococci) are reliable indicators of faecal contamination in Hawaii's environmental waters. The QPCR assay for the human-specific Bacteroides 16S rRNA marker was faster, more sensitive and more reliable than comparable SPCR assay because OPCR assay provided additional information such as melting temperatures, which confirmed that the right amplicons were being measured and Ct values, which indicated the relative level of faecal contamination.     

Experience with the antibiotic resistance analysis and DNA fingerprinting in tracking faecal pollution at two lake beaches.

Posting or closing of swimming beaches because of faecal contamination is a widespread problem reported in many locations. In a risk-based approach to this problem, the risk to swimmers' health is assessed by field monitoring of indicator bacteria and the associated risks are managed by source controls and other remedial measures. In risk assessment, great advances have been made in recent years with the introduction of microbial source tracking (MST) techniques. Two such techniques, antibiotic resistance analysis and DNA fingerprinting, were applied in a study of causes of faecal contamination at two lake beaches in Toronto, Ontario. Both methods identified bird faeces as the dominant sources of E. coli. Coping with this type of pollution presents a major environmental challenge.     

Spatial effects of reservoirs on fish assemblages in Great Plains streams in Kansas,USA

Reservoirs are important components of modern aquatic ecosystems that have negative impacts on native aquatic biota both up‐ and downstream. We used a landscape‐scale geographic information system (GIS) approach to quantify the spatial effects of 19 large reservoirs on upstream prairie fish assemblages at 219 sites in Kansas, USA. We hypothesized that fish assemblage structure would vary with increasing distance from a reservoir and that the abundance of reservoir fishes in upstream reaches would decline with distance from a reservoir. Ordination of sample sites showed variation in fish assemblage structure occurred primarily across river basins and with stream size. Variance partitioning of a canonical ordination revealed that the pure effect of reservoir distance explained a small but significant (6%; F = 4.90, P = 0.002) amount of variability in fish assemblage structure in upstream reaches. Moreover, reservoir species catch per unit of effort (CPUE) significantly declined with distance from a reservoir, but only in fourth‐ and fifth‐ order streams (r² = 0.32, P < 0.001 and r² = 0.49, P < 0.001, respectively). Finally, a multivariate regression model including measures of stream size, catchment area, river basin, and reservoir distance successfully predicted CPUE of reservoir species at sites upstream of Kansas reservoirs (R² = 0.45, P < 0.001). Overall, we found significant upstream effects of reservoirs on Kansas stream fish assemblages, which over time has led to a general homogenization of fish assemblages because of species introductions and extirpations. However, characteristic reservoir species are present throughout these systems and the importance of spatial proximity to reservoirs is probably dependent on the availability of suitable habitat (e.g. deep pools) in these tributary streams. Copyright © 2005 John Wiley & Sons, Ltd.     

Characterization of water quality in a small hydropower plant reservoir in southern Brazil

The construction of large reservoirs can cause profound environmental changes. Reduced water flow, increased water residence time, thermal stratification, increased sedimentation rates and decreased dissolved oxygen concentrations are examples of such changes. These changes can affect water quality and the biota in the environments adapted to the natural conditions of a river. Small reservoirs developed in conjunction with hydropower plants, however, could reduce the degraded water quality. This study focuses on characterizing water quality in a small hydroelectric reservoir. The study reservoir has an area of 1.4 km² and a short water retention time. The Monte Claro Hydroelectric Power Plant is part of a complex consisting of three plants on the Antas River in the north‐west of Rio Grande do Sul state, Brazil. The reservoirs associated with these plants are operated as run‐of‐the‐river facilities. Monitoring results obtained by CERAN, the Energetic Company of Antas River (Companhia Energética Rio das Antas), were used to evaluate the reservoir water quality. Three samples were collected seasonally (spring, summer, autumn and winter) in the area of influence of this plant following the filling of the reservoir (2005–2008). The examined water quality parameters were electrical conductivity, colour, turbidity, alkalinity, pH, biological oxygen demand (BOD), chemical oxygen demand (COD), total phosphorus, dissolved oxygen, sulphate, nitrate, nitrite, ammonia, suspended and dissolved solids, chlorophyll‐a, total and faecal coliforms, water temperature and Secchi depth transparency. The results were interpreted using an index of water quality, Trophic State Index, reservoir water quality and CONAMA Regulation 357/05 (Brazilian legislation). Based on these analyses, no significant changes were exhibited in the water quality of the reservoir from the hydroelectric plant operation.     

Biodiversity characteristics of small high-altitude tropical man-made reservoirs in the Eastern Rift Valley, Kenya

The biodiversity characteristics in eight small (0.065–0.249 km²) public man‐made reservoirs in the central part of the Eastern Rift Valley, Kenya, were studied between 1995 and 1998. A total of 71 phytoplankton species belonging to approximately 50 taxa were identified. Chlorophytes and cyanobacteria dominated the crop. The dominant taxa included Botryococcus, Syunura, Microsystis, Anabaena, and Cosmarium. A total of over 40 zooplankton species were identified. The community was composed mainly of crustacea, rotifers and protozoa. The most dominant group was Keratella but Brachionus and Nauplius were equally abundant. The diversity and abundance of benthic invertebrates was not high, and only 18 species were identified throughout the study period with the range of species number being 1–7 per reservoir. The benthic fauna was mainly composed of Lumbriculidae and Chironomid worms. A total of six monthly bird counts found an average of 60 birds per reservoir, and a total of 49 species was identified. Ducks, geese and coots dominated the waterfowl, especially during the dry season. Large‐scale breeding by Black‐headed Heron (Ardea melanocephala ) and Little Egret (Egretta garzetta ) was observed in one of the sites, and other species were also breeding in the reservoirs. The population of waterbirds in reservoirs was closely related to the biomass of benthic invertebrates, and the findings of the study indicate that the structure and dynamics of life forms within small man‐made reservoirs can serve as excellent sensors and indicators of the state of watershed health.     

Multi‐dimensional effects on Cladoceran (Crustacea,Anomopoda) assemblages in two cascade reservoirs in Southeast Brazil

The Cladocera assemblages in two cascade reservoirs located in the Paranapanema River in Brazil were studied during two consecutive years. Upstream Chavantes Reservoir is an accumulation system, with a long water retention time, high depth and oligo‐mesotrophic status. The downstream Salto Grande Reservoir is a small, run‐of‐river reservoir, with a short water retention time, shallow depth and meso‐eutrophic status. The goal of this study was to determine the inter‐ and intra‐reservoir limnological differences with emphasis on the Cladocerans assemblages. The following questions were posed: (i) what are the seasonal dynamics of the reservoir spatial structures; (ii) how dynamics, seasonally, is the reservoirs spatial structure; and (iii) are the reservoir independent systems? A total of 43 Cladoceran species were identified in this study. Ceriodaphnia silvestrii was the most abundant and frequent species found in Chavantes Reservoir, while C. cornuta was most abundant and frequent in Salto Grande Reservoir. The Cladoceran species richness differed significantly among sampling sites for both reservoirs. In terms of abundance, there was a significant variation among sampling sites and periods for both reservoirs. A cluster analysis indicated a higher similarity among the deeper compartments, and the intermediate river‐reservoir zones was grouped with the riverine sampling sites. For the smaller Salto Grande Reservoir, the entrance of a middle size tributary causes major changes in the system. A distinct environment was observed in the river mouth zone of another small tributary, representing a shallow environment with aquatic macrophyte stands. A canonical correlation analysis between environmental variables and Cladoceran abundance explained 75% of the data variability, and a complementary factorial analysis explained 65% of the variability. The spatial compartmentalization of the reservoirs, as well as the particular characteristics of the two study reservoirs, directly influenced the structure of the Cladoceran assemblages. The conditions of the lacustrine (dam) zone of the larger Chavantes Reservoir were reflected in the upstream zone of the smaller downstream Salto Grande Reservoir, highlighting the importance of plankton exportation in reservoir cascade systems. The comparative spatial–temporal analysis indicated conspicuous differences between the two reservoirs, reinforcing the necessity of considering tropical/subtropical reservoirs as complex, multi‐compartmental water systems.     

Dispersal of Contaminants from Municipal Discharges as Evidenced from Sedimentary Records in a Great Lakes Coastal Wetland,Cootes Paradise,Ontario

Cootes Paradise is a coastal wetland, at the western end of Lake Ontario. The marsh, which is an important spawning ground for fish and a crucial habitat for other species, has been considerably degraded by excessive contaminant inputs from wastewater treatment plants (WTPs), marsh tributaries, and Combined Sewer Overflows (CSOs). These discharges are not only major sources of nutrients (e.g., phosphorus) to the marsh, but are also the main contributors of pharmaceuticals, hormones, and other wastewater contaminants. Studies have shown that many of these compounds are toxic and have estrogenic effects on organisms living in the vicinity of these sources. This study investigates dispersal of contaminants from nearby point sources, as determined from sediment contamination, both spatially and stratigraphically. This was accomplished by establishing the trends and utilizing the relationships between limiting nutrient phosphorus, estrogenic alkylphenols, and faecal sterols, specifically, coprostanol. High levels of phosphorus (1,655–1,987 mg TP kg⁻¹) and alkylphenolics (2.51–4.89 mg kg⁻¹) were measured in sediments near the discharge outlets. Statistical analysis revealed a close relationship between investigated pollutants and the molecular marker coprostanol, and provides evidence of significant sediment contamination near the discharge points, suggesting deposition of most contaminants within a short distance from the points of entry and limited dispersal of pollutants within the wetland. The stratigraphic distribution of pollutants, which reflects the historical trends, reveals major spikes in pollutant concentrations near point sources that could be attributed to episodic events of major significance and shows a long persistence of the investigated contaminants in sedimentary environments.     

Observed and predicted occurrence of blackflies (diptera: Simuliidae) at fifty reservoir outlets in Britain

The blackflies present at 50 reservoir outlets throughout mainland Britain were recorded. The observed occurrence of simuliid taxa at sites below upland and lowland reservoirs was compared with the predicted occurrence using predictive equations based on environmental variables. Below the upland reservoirs five simuliid taxa which were predicted to occur were not recorded. Of these S. reptans gp showed the widest discrepancy between predicted and observed occurrences. Four taxa were recorded at significantly fewer sites than predicted and a further four were present at a small number of sites, not differing greatly from the predicted frequency. A similar pattern was observed at the lowland reservoir outlets but S. noelleri, a species frequently associated with lake outlets, was present at more sites than predicted. The influence of a reservoir's presence on the simuliid community is discussed in relation to the known requirements of the species occurring and those predicted to occur.     

Cladocera assemblages from reservoirs in Sri Lanka and their relationship to measured limnological variables

The potential of using surface‐sediment assemblages of Cladocera as bioindicators for reservoirs in Sri Lanka was assessed for their subfossil remains, along with contemporary physical and chemical measurements from each reservoir. The reservoirs span five climatic regions, from extremely arid environments to tropical montane forests, as well as three orders of magnitude changes in many physical and chemical variables. In total, although the remains of 39 Cladocera taxa from 21 genera were identified, only 31 taxa from 37 sites were present at sufficiently high abundances to assess their relation to measured environmental variables. Canonical correspondence analysis (CCA) identified surface area, maximum depth and chloride as the three most important measured environmental variables that could account for the variation in the cladoceran assemblages. Taxa such as Chydorus sphaericus, Alona aff. verrucosa and Leydigia acanthocercoides were more abundant in generally deeper, larger reservoirs, whereas Alonella excisa, Euryalona orientalis, Notoalona globulosa and Chydorus eurynotus were more abundant in shallow smaller reservoirs. Although there was a strong separation between climatic zones in terms of factors related to specific conductance, this factor only appears marginally important in separating cladoceran assemblages. Quantitative inference models developed to assess the strength of inferring environmental variables using partial least squares regression and calibration were all relatively weak, with jackknifed coefficient of determination values of 0.40, 0.28 and 0.27 for surface area, maximum depth and chloride, respectively. These results, in conjunction with large differences in eigenvalues between constrained and unconstrained ordinations, suggest that unmeasured environmental variables are also important in structuring cladoceran assemblages.     

Microbial source tracking to identify fecal sources contaminating the Toronto Harbour and Don River watershed in wet and dry weather

Identification of sources of fecal pollution in urban areas is critical for protecting public health, the environment, and guiding remediation. We collected 670 water samples at 46 sites in 2018 to study fecal pollution in the Toronto Harbour and Don River watershed. Water samples were analyzed for E. coli, wastewater chemicals, and microbial source tracking DNA markers using a digital PCR technique. Microbial DNA markers were useful for interpreting the sources of elevated E. coli concentrations in the study. The HF183 marker for human sewage was the most frequently detected DNA marker, occurring in 100% of samples taken from the Don River and associated outfalls. It was also frequently detected in the Inner Harbour and outfalls along the Toronto harbour front. It was detected less frequently and at lower levels in the outer harbour. Detection of a human mitochondrial DNA marker and wastewater chemical markers such as caffeine provided additional evidence of widespread sewage contamination. The gull DNA marker was widely detected, but at lower frequencies and levels than human source DNA markers. A wet weather response of increased E. coli and human DNA marker concentrations occurred at most sites. However, human DNA markers were also widely detected on dry weather sampling days, indicating sewage cross-connections in stormwater and dry weather CSO systems. The cumulative impact of cross-connected stormwater outfalls is likely an under-recognized source of sewage contamination. E. coli and HF183 DNA marker levels observed can serve as benchmarks for evaluating future water quality improvements from wastewater infrastructure investments.     

Vegetation development and restoration potential of drained reservoirs following dam removal in Wisconsin

Dam removal is potentially a powerful tool for river and riparian restoration. However, long‐term studies on the fate of former reservoirs do not exist, limiting assessment of the utility of dam removal as a means of riparian restoration. We took advantage of the decades‐long legacy of dam removals in Wisconsin to determine human uses of drained reservoirs and to evaluate vegetation establishment and species replacement at these sites. More than half of the 30 dam removal sites in southern Wisconsin over the past 47 years were used as commercial areas, parks and agricultural land, and active riparian restoration occurred on only two sites. For the 13 sites that were allowed to revegetate on their own, plants established in the first growing season and cover was very high at all sites in 2001. Species diversity and frequency (defined as percentage of sampled quadrats where a species is present) of trees were positively correlated with time since removal. No relationship existed between site age and frequencies of other growth forms, nor were there significant relationships between site age and the number or frequency of introduced species. However, mean frequency of introduced species was 75% per site and several sites were dominated by the introduced grass Phalaris arundinacea. Frequency of P. arundinacea was negatively correlated with number of native forbs, and lowest species diversity occurred on sites dominated by P. arundinacea. Ordination analyses revealed substantial site‐to‐site variation in vegetation that was weakly associated with gradients of site location, age, area, and soil phosphorus. Thus, temporal vegetation dynamics following dam removal were site‐specific. Rapid revegetation demonstrates the potential of these sites for riparian restoration. However, if dam removal is used as a means of restoring native riparian communities, then approaches must be tailored to individual sites and will need to focus on techniques to minimize establishment of aggressive invading species. Copyright © 2006 John Wiley & Sons, Ltd.     

Hybridisation of F+ RNA coliphages detected in shellfish samples with oligonucleotide probes to assess the origin of microbiological pollution of shellfish.

Current measures for controlling the public health risks associated with bivalve molluscan shellfish consumption rely on the use of Escherichia coli to indicate the sanitary quality of shellfish harvesting areas. However, it has been demonstrated that E. coli is an inadequate indicator of the viral risk associated with shellfish. An alternative indicator, male-specific B+ coliphages, have been investigated as viral indicators of faecal contamination that may provide source-specific information for impacted environmental waters. This study compared the distribution of E. coli and F+ RNA bacteriophages in shellfish grown in harvesting areas of Greece and also examined the presence and proportions of the different subgroups of F+ RNA coliphages in shellfish. F+ RNA bacteriophages were present in shellfish at higher concentrations than E. coli. Elevated numbers of F+ RNA bacteriophages observed in the winter concur with the known increased viral risk associated with shellfish harvested at that time of year in Greece. The majority of F+ RNA coliphages detected in shellfish samples belonged to group IV which indicated the possible presence of animal faecal material in sample harvesting areas. Phages of groups II and III (human waste and human faecal material, respectively) were present at low levels. Finally, 8% of the phages hybridised were found to belong to group I. The presence of group IV showed seasonal distribution (more in winter, less in summer) whereas the other groups did not show any difference. Monitoring of F+ coliphage subgroups may indicate the presence and major sources of microbial inputs to surface waters; however, environmental effects on the relative occurrence of different groups need to be considered.