The Experts below are selected from a list of 3162 Experts worldwide ranked by ideXlab platform
N F Gray - One of the best experts on this subject based on the ideXlab platform.
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acid mine drainage composition and the implications for its impact on Lotic Systems
Water Research, 1998Co-Authors: N F GrayAbstract:Abstract Intensive sampling of acid mine drainage from adits draining the abandoned copper and sulphur mines at Avoca, south-east Ireland, has confirmed a seasonal variation in the Zn:Cu ratio observed previously. The variation in the Zn:Cu ratio leads to extreme variations in the toxicity of the drainage, and linked with increased adit flows and surface runoff during wetter months, often results in higher river toxicity, even during high river discharge rates. This seasonal variation in toxicity has important ramifications for the control of AMD to surface waters. Sampling over a three-year period shows that the rate of discharge from the adits follows a seasonal cycle being high in the spring, declining through summer to reach lowest flows in autumn and rising again in the winter. During the intensive sampling study over a 13-month period, the discharge rate in the Deep Adit varied from 8.5 to 37.3 l/s compared to 6.3 to 35.2 l/s in the Ballymurtagh Adit. This represents a total discharge rate for the two adits of between 1265 and 6270 m3/d. Significant weights of cations were discharged from the two adits, ranging from 169–1279 kg/d for Fe, 69–459 kg/d for Zn, 1.5–34.7 kg/d for Cu, and 0.167–0.875 kg/d for Cd, with the Deep Adit contributing on average 40.4, 70.4, 66.7 and 80.9% of each metal respectively over the sampling period of 13 months. The impact of AMD on the river biota is severe with a major decrease in the number of taxa and faunal abundance. The species deficit at all sites below the mines is in excess of 87%. Dipterans dominate impacted sites with Chironomidae abundant. Fish are eliminated except for juvenile eels close to the estuary.
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a substrate classification index for the visual assessment of the impact of acid mine drainage in Lotic Systems
Water Research, 1996Co-Authors: N F GrayAbstract:The impact of acid mine drainage (AMD) on Lotic receiving waters is complex and difficult to assess. While low pH, elevated sulphate and metals all characterize AMD these vary both spatially and temporally, with high river dilutions resulting in low absolute concentrations which are difficult to measure. From field observations the best indications of AMD contamination of Lotic Systems appear to be the brownish-yellow precipitates of iron (III) hydroxide, high densities of chironomids, and the absence of macrophytes. Using these observations a simple index based on the degree of deposition of ochre on the river substrate, and the level of floc formation, has been devised. The index is purely a descriptive one and is calculated rapidly using a visual inspection of individual sites. The derived index values are related to the biological impact that can be expected.
Eduardo A Lobo - One of the best experts on this subject based on the ideXlab platform.
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Assessment of potential reference sites for evaluating the ecological status of subtropical and temperate Brazilian Lotic Systems using the epilithic diatom community
Environmental Science and Pollution Research, 2020Co-Authors: Núbia Cristina Weber Freitas, Carla Giselda Heinrich, Tanise Etges, Gleison Souza Celente, Eduardo A LoboAbstract:This research aimed at determining reference sites in southern Brazilian Lotic Systems, using the Water Quality Trophic Index (WQTI), based on epilithic diatom communities. Within the period of 2012 and 2016, 140 epilithic diatom samples from seven sampling sites within the spring area of the Andreas Stream Hydrographic Basin, Vera Cruz County, RS, Brazil, were analyzed quarterly. Similarly, from 2012 and 2014, water samples in these sampling sites were collected for determination of physicochemical and microbiological parameters, such as water temperature, pH, turbidity, dissolved oxygen, biochemical oxygen demand, nitrate, phosphate, total dissolved solids, and fecal coliforms. The results indicated the occurrence of two diatom samples groups with significant differences ( p < 0.05). Group 1 (sampling sites P1, P4, and P5) was classified in the oligotrophic category with an average WQTI of 1.3 ± 0.2, while group 2 (sampling sites P2, P3, P6, and P7) was classified in the β-mesotrophic category with an average value of 2.0 ± 0.4). Achnanthidium minutissimum and Platessa hustedtii the dominant species were classified as oligotrophic taxa. Thus, we proposed the upper limit of the first interval of the WQTI score scale, equal to 1.5, as a reference value to differentiate the limits between the “high” and “good” ecological status to determine “reference sites” for subtropical and temperate Brazilian aquatic Systems. The physical, chemical, and microbiological water quality evaluation gives support to this proposal, as far as the results indicated a significant improvement in the water quality, classifying sampling sites P1, P4, and P5 as having good quality appropriate for multiple uses.
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development of the trophic water quality index twqi for subtropical temperate brazilian Lotic Systems
Environmental Monitoring and Assessment, 2015Co-Authors: Eduardo A Lobo, Marilia Schuch, Carla Giselda Heinrich, Adilson Ben Da Costa, Adriana Dupont, Carlos E Wetzel, Luc EctorAbstract:This research aimed at developing the Trophic Water Quality Index (TWQI) for subtropical temperate Brazilian Lotic Systems based on a review of the indicative values of diatom species obtained using multivariate analysis techniques and considering the environmental gradient defined by a series of measured physical, chemical, and microbiological variables. Sampling was conducted from 2005 to 2009 in the Pardo River Hydrographic Basin, Rio Grande do Sul (RS), Brazil, and in the Andreas Stream Hydrographic Basin, RS, from 2012 to 2013. A total of 140 biological samples and 211 abiotic samples were collected. Data were analyzed by cluster analysis based on the Ward method and canonical correspondence analysis (CCA). The results indicated that total phosphate, turbidity, ammonia nitrogen, electrical conductivity, dissolved oxygen, and thermotolerant coliforms showed a significant correlation with the sample ordination made by CCA, in relation to a gradient of eutrophication. Eutrophication was operationally defined in a broad sense, including the problem of organic pollution and eutrophication of the water. The determination of the different tolerance degrees to eutrophication of the diatom taxa was used to assign trophic values of 1, 2.5, and 4 to species, corresponding to levels of low, medium, and high tolerance, respectively. By using the trophic values obtained for each diatom species, the TWQI constituted a new technological tool for environmental monitoring studies and showed a consistent, robust, and objective database for water quality assessment in subtropical temperate Brazilian Lotic Systems.
Vladica Simic - One of the best experts on this subject based on the ideXlab platform.
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the utility of two marine community indices to assess the environmental degradation of Lotic Systems using fish communities
Science of The Total Environment, 2016Co-Authors: Milica Stojkovic Piperac, Djuradj Milosevic, Snežana B Simic, Vladica SimicAbstract:Multimetric approaches are commonly used to evaluate the ecological status of aquatic ecoSystems. However, it has been recommended that the sensitivity of existing methods be improved through the investigation of the potential of new metrics to detect environmental disturbances. In this study we tested the effectiveness of two community indices (Taxonomic distinctness index (TDI) and Abundance biomass comparison (ABC) method), primarily proposed for marine ecoSystems, to identify sites with different levels of environmental degradation in Lotic Systems using fish community data. Fish samples were collected over the period 2003–2011 at 131 sampling stations. To generate water and habitat quality classes, a self-organizing map (SOM) based on environmental data was applied. Gradients over the SOM map were investigated for the values of the TDI and ABC indices. The results of this study reveal that the values of both the TDI and ABC indices are highly correlated with water and habitat quality gradients. However, despite the observed correlation, the utility of TDI as a potential metric in bioassessment programs is rather limited, due to its lack of discriminatory power. In contrast, the ABC method could be proposed as a novel metric, but can only be applied in type-specific multimetric approaches.
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the application of the abundance biomass comparison method on riverine fish assemblages limits of use in Lotic Systems
Biologica Nyssana, 2015Co-Authors: Milica Stojkovic Piperac, Djuradj Milosevic, Vladica SimicAbstract:Fish assemblages have been widely used as ecological indicators for assessing the level of environmental degradation and ecosystem health. Environmental disturbances affect the aquatic community structure in terms of abundance and biomass. Therefore, we tested the utility of abundance/biomass comparison (ABC) method, originally developed for marine ecoSystems, to detect the anthropogenic disturbance in Lotic Systems using fish community data. Electrofishing was conducted in the period between 2003 and 2011 at 35 sites along the Southern Morava River basin. The results indicated that species richness strongly influences the utility of ABC method to detect the anthropogenic disturbance in Lotic Systems. The Warwick (W) statistic showed the positive correlation and the expected direction of response with some factors defining environmental quality, applying it on the samples with greater species richness. This approach has significant power for detecting environmental quality disturbance but may be limited due to effects of habitat variability in riverine environments.
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using a fish based model to assess the ecological status of Lotic Systems in serbia
Water Resources Management, 2014Co-Authors: Milica Stojkovic, Djuradj Milosevic, Snežana B Simic, Vladica SimicAbstract:Fish biotic indices have become common tools for measuring and monitoring the ecological status of aquatic ecoSystems. In this study, we aimed to develop the first fish-based model for stream quality assessment in Serbia taking into account the regional specificity of the country. Fish samples were collected between 2003 and 2011 at 131 sampling sites. We employed a self-organizing map (SOM) in order to group samples into river types depending on the character of the habitat they came from. Next, the k-means cluster analysis classified samples into four groups, each describing a particular ecological condition. The indicator species were presented for each group based on their constancy and dominance. Gradients over the SOM map were sought for 17 fish community metrics. On the basis of the core metrics and selected indicator species, we proposed a fish-based index for the assessment of the ecological status of running waters in Serbia.
Sean M Richards - One of the best experts on this subject based on the ideXlab platform.
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is ambient chitobiase activity a monitoring tool for impacts on secondary production in Lotic Systems
Canadian Journal of Fisheries and Aquatic Sciences, 2009Co-Authors: Justin M Conley, Mark S Schorr, Mark Hansonm L L Hanson, Steven Symess J J Symes, Sean M RichardsAbstract:Chitobiase is one of two enzymes responsible for cleaving the chitin polymers that form arthropod exoskeletons and has been found to be predictive of secondary production for marine and freshwater ...
E. A. Fano - One of the best experts on this subject based on the ideXlab platform.
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Environmental stressor gradients hierarchically regulate macrozoobenthic community turnover in Lotic Systems of Northern Italy
Hydrobiologia, 2016Co-Authors: V. G. Aschonitis, C. K. Feld, G. Castaldelli, P. Turin, E. Visonà, E. A. FanoAbstract:Environmental stressors present a hierarchical influence on freshwater organisms. This study investigates the hierarchy of environmental stressor gradients, which regulate the composition of instream macroinvertebrate communities of northern Italy (Po Valley and the south-eastern Alps). Species and environmental data were derived from 585 monitoring sites. Environmental parameters were split into three groups, describing (i) ecoregional, (ii) hydromorphological, and (iii) water quality attributes. Partial Redundancy Analysis (partial RDA) was used to hierarchically rank the group effects, which were expressed as unique (group specific) and joint effects (of two groups together). Overall, ecoregion explained more variance (30.2%) than hydromorphology (24.8%) and water quality (22.3%). Unique effects were generally low, but ecoregional unique effects were twice as high as those of the other groups. The analysis of single environmental variables highlighted significant effects of anthropogenic impact related to the substrate size composition, riparian vegetation, flow conditions, and Escherichia coli (surrogate descriptor of organic fecal pollution). Such stressor hierarchies can support biodiversity conservation plans, while the high joint effects of stressor groups suggested the need for combined management activities, addressing the respective stressors and stressor groups in concert. Management measures addressing only one stressor group isolated from others are likely to be less effective, or even ineffective.
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relations between environmental gradients and diversity indices of benthic invertebrates in Lotic Systems of northern italy
Web Ecology, 2016Co-Authors: V. G. Aschonitis, G. Castaldelli, E. A. FanoAbstract:Abstract. The relations between environmental gradients, as measured by 19 independent variables, and traditional diversity indices (taxonomic richness, diversity and evenness) of benthic macroinvertebrate communities in the Lotic Systems of northern Italy were analyzed. Redundancy analysis (RDA) was used to describe the response of taxa to environmental gradients. Diversity indices were analyzed using generalized linear models (GLMs) with explanatory variables the first two major RDA axes. The results from RDA showed that taxa variance is mostly explained by altitude/latitude and combined pollution gradients. Taxonomic richness and diversity was higher in the low polluted upland sites (LPUs) in comparison to high polluted lowland sites (HPLs), suggesting that headwater streams have higher taxonomic richness than downstream reaches. On the other hand, evenness was lower in LPUs, probably due to the dominance of some taxa (e.g., Plecoptera) that are more tolerant of colder conditions.
