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Context: Alterations of landscapes and riverscapes by humans have fundamentally altered patterns in freshwater biodiversity throughout the world's aquatic systems. Past research has demonstrated precipitous declines in small- and medium-sized streams, with much less attention given to patterns and drivers of fish biodiversity in larger riverine systems. Objectives: By examining alpha and beta diversity of fishes in the middle and lower reaches of the Yangtze River, China, we aimed to address the following question: What is the role of river–lake connectivity, wetland extent, and human stress factors (e.g., urbanization, fishing pressure, navigation, and shoreline modifications) in shaping fish alpha (species richness) and beta (species nestedness and turnover) diversity? Methods: We examined associations among three classifications of fish assemblage data (i.e., all species, nonmigratory species, and migratory species) sampled along gradients of river–lake connectivity (i.e., Dongting and Poyang lakes), wetland extent, and a suite of human stress factors (urbanization, fishing pressure, navigation, shoreline modification). We conducted redundancy analyses and distance-based redundancy analyses to facilitate mechanistic interpretations of the associations between the explanatory variables and fish alpha and beta diversity. Results: Longitudinally from the middle to the lower reaches of the Yangtze River, fish alpha diversity showed marked decreases while fish beta diversity increased. River segments with greater levels of human impact were generally associated with reduced fish species richness, while segments with higher wetland extent and greater river–lake connectivity tended to support greater species richness. River–lake connectivity, wetland extent, and fishing pressure largely influenced total fish beta diversity. Species nestedness was primarily associated with amount of wetlands, and exhibited the strongest associations with nonmigratory fish species. Turnover was primarily associated with river–lake connectivity (mainly Poyang Lake), especially for migratory species. Conclusions: Our analyses demonstrate the roles of river–lake connectivity, wetland extent, and human stress factors in shaping patterns of alpha and beta diversity for migratory and nonmigratory fishes in the middle and lower reaches of the Yangtze River. Fish diversity conservation in this large river ecosystem calls for protecting hydrological connectivity and wetland habitats, along with reducing fishing pressure. Results from this study will help better inform fish conservation efforts in the Yangtze River and have implications towards other large river systems of the world. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to establish a near infrared fluorescent (NIRF) probe based on an EGFR&c-Met bispecific antibody for visualization of esophageal cancer (EC) and metastatic lymph nodes (mLNs). Methods: EGFR and c-Met expression were assessed by immunohistochemistry. EGFR&c-Met bispecific antibody EMB01 was labeled with IRDye800cw. The binding of EMB01-IR800 was assessed by enzyme linked immunosorbent assay, flow cytometry, and immunofluorescence. Subcutaneous tumors, orthotopic tumors, and patient-derived xenograft (PDX) were established for in vivo fluorescent imaging. PDX models using lymph nodes with or without metastasis were constructed to assess the performance of EMB01-IR800 in differential diagnosis of lymph nodes. Results: The prevalence of overexpressing EGFR or c-Met was significantly higher than single marker either in EC or corresponding mLNs. The bispecific probe EMB01-IR800 was successfully synthesized, with strong binding affinity. EMB01-IR800 showed strong cellular binding to both Kyse30 (EGFR overexpressing) and OE33 (c-Met overexpressing) cells. In vivo fluorescent imaging showed prominent EMB01-IR800 uptake in either Kyse30 or OE33 subcutaneous tumors. Likewise, EMB01-IR800 exhibited superior tumor enrichment in both thoracic orthotopic esophageal squamous cell carcinoma and abdominal orthotopic esophageal adenocarcinoma models. Moreover, EMB01-IR800 produced significantly higher fluorescence in patient-derived mLNs than in benign lymph nodes. Conclusion: This study demonstrated the complementary overexpression of EGFR and c-Met in EC. Compared to single-target probes, the EGFR&c-Met bispecific NIRF probe can efficiently depict heterogeneous esophageal tumors and mLNs, which greatly increased the sensitivity of tumor and mLN identification. [ABSTRACT FROM AUTHOR]

Objective: To improve the current imaging understanding of MRI or CT for hepatic epithelioid haemangioendothelioma (HEHE) to aid in its successful preoperative diagnosis. Methods: The imaging features of 15 patients (median age 38.6, range 20–71; 7 M/8 F) from eight institutions with pathologically confirmed HEHE were retrospectively analysed. Additionally, the CT/MR imaging features of 180 patients in 15 literature publications were collected, analysed and compared with our case series. Results: Fifteen patients underwent CT and MRI (n = 2), CT (n = 9) or MR (n = 8) scans. A total of 92.9% (13/14) of the patients were initially diagnosed with other lesions on imaging. A total of 86.7% (13/15) were multifocal. Nodules (11/15, 73.3%) were predominantly peripheral in distribution (12/15, 80.0%). Some cases were associated with hepatic capsular retraction (13/15, 86.7%), "target signs" (8/15, 53.3%) and "lollipop signs" (5/15, 33.3%). Peripheral enhancement of various shapes in the early phase with a progressive centripetal filling was the most common pattern of enhancement (12/15, 80.0%). Abnormal vascularity was seen in 50.7% (6/15) of the patients. Suspicious tumour thromboses in the inferior vena cava were seen in 3 (20.0%) of the patients. Two of the 15 patients (13.3%) had a history of smoking. Conclusions: HEHEs have common distinctive features, including multifocal lesions that are predominantly peripheral, "target signs", "lollipop signs", hepatic capsular retraction and peripheral enhancement of various shapes in the early phase with progressive centripetal filling. Additional aggressive imaging features that may be valuable clues to the diagnosis can be identified by CT or MRI. Key points: "Target signs" and "lollipop signs" should be recognised in imaging evaluation, raising the possibility of HEHE in the differential diagnosis. Abnormal blood vessels in tumours may have implications for imaging diagnosis. When HEHE is suspected, radiologists should be aware of tumour thrombi in the vena cava. HEHEs always present with a peripheral enhancement of various shapes with centripetal progressive filling. [ABSTRACT FROM AUTHOR]

Concrete is a typical porous heterogeneous material. Avalanches during concrete failure release acoustic emission (AE) signals. The statistical characteristics of avalanches of concrete compression failure under sulfate attack were investigated by AE. The distribution of absolute energy, amplitude, duration, and correlations between amplitudes and energies satisfied the power law. For the initial enhancement stage of sulfate attack, the values of the avalanche exponents closer to the mean field model prediction. For the subsequent deterioration stage, the values of the avalanche exponents closer to the force integrated mean field model prediction. The variations in the avalanche exponents corresponded to the variations in the mechanical properties and mesostructure of concrete under sulfate attack. Waiting time distribution and aftershock (AS) decay showed robustness during the sulfate attack. Avalanche characteristics can help to understand the failure mechanism of concrete under sulfate attack, and the exponents of avalanche distributions provide a new way to characterize the degree of corrosion. [ABSTRACT FROM AUTHOR]

Tourism remains one of the top threats in nature reserves worldwide. In this study, we first used both a field survey and in situ nutrient enrichment experiments to assess the effects of tourisms on aquatic ecosystems in a World Natural Heritage site that includes lakes, streams, shoals, and waterfalls. The results showed that phosphorus (P) enrichment altered benthic algal assemblage composition and the color of bryophyte-dominated benthic substrates in a shoal. Epilithic diatoms and their responses to the nutrient addition were significantly different between the control and test sites on a lake, which had contrasting tourist impacts in a lake. Second, we assessed the resilience of a lake heavily visited in the reserve by comparing phytoplankton density before and after a 2-year reserve closure due to an earthquake. Our study confirmed the hypotheses: (1) the perceived color change in Jiuzhaigou Natural Reserve waters was caused by nutrient enrichment in relation to tourist activities and was closely associated with a shift in algal composition; and (2) the changes to the fluvial and lake systems are still at their early stages and could be recovered by reducing tourism pressure. Our findings provide managers of protected karstic nature reserves with critical information for identifying causes of reserve degradation, estimating the carrying capacity for tourism and establishing limits of acceptable ecosystem changes. Guiping Deng (deceased) [query] [ABSTRACT FROM AUTHOR]

It is common to obtain the topography of tidal flats by the Unmanned Aerial Vehicle (UAV) photogrammetry, but this method is not applicable in tidal creeks. The residual water will lead to inaccurate depth inversion results, and the topography of tidal creeks mainly depends on manual survey. The present study took the tidal creek of Chuandong port in Jiangsu Province, China, as the research area and used UAV oblique photogrammetry to reconstruct the topography of the exposed part above the water after the ebb tide. It also proposed a Trend Prediction Fitting (TPF) method for the topography of the unexposed part below the water to obtain a complete 3D topography. The topography above the water measured by UAV has the vertical precision of 12 cm. When the TPF method is used, the cross-section should be perpendicular the central axis of the tidal creek. A polynomial function can be adapted to most shape of sections, while a Fourier function obtains better results in asymmetrical sections. Compared with the two-order function, the three-order function lends itself to more complex sections. Generally, the TPF method is more suitable for small, straight tidal creeks with clear texture and no vegetation cover. [ABSTRACT FROM AUTHOR]

Context: Untangling relationships between landscape patterns shaped by human stressors and related response of fish communities is important for identifying biodiversity patterns and conservation targets, yet in large rivers this knowledge is extremely limited. Objectives: Our study focuses on how human stressors within a riparian landscape zone, including both riparian land use and in-channel stressors, explained the fish community structure in a large river. Methods: We studied fish community patterns along the upstream-downstream gradient of the Yangtze River, China. The curve estimation was used to test correlations between fish metrics and the distance from the estuary. We linked human stressors to fish metrics by multivariate generalized linear models. Results: We collected a total of 63 freshwater fish species from 6,147 specimens. Limnophilic species had the highest richness, represented by 30 specie. The predominant riparian land uses in the studied reaches were cropland (65.3% ± 13.1%) and urban land (19.7% ± 13.6%). There were strong negative correlations between riparian land use (e.g., urban land) and in-channel stressors (e.g., shoreline modification, navigation, and fishing pressure) and fish assemblages, especially limnophilic fish abundance, biomass, and richness. Conclusions: These results demonstrate influences of both riparian land use and in-channel stressors on fish communities, and highlight the use of landscape descriptors as a valuable approach to assess linkages between human pressures and fish diversity in large river systems. Management recommendations include: establishing or rehabilitating riparian buffers, improving commercial navigation management, implementing shoreline protection measures, and reinforcing fishing laws and regulations. [ABSTRACT FROM AUTHOR]

Understanding how long-term environmental variation and biotic interaction determine biological assemblages is critical for evaluating the response of biological communities to anthropogenic and climate changes. We sampled plankton and water quality from a man-made lake monthly from 2006 to 2015 for the period from after creation to 13-year old of the lake. We used correlation, variation partitioning, multivariate autoregressive state-space models, and dynamic factor analyses to disentangle interactions of biotic and abiotic factors in regulating the dynamics of plankton size groups. We found that annual average total abundances decreased 86% for phytoplankton and 78% for zooplankton, while concentrations increased 1.8 times for total nitrogen and 2.7 times for total phosphorus during the study period. We concluded that the decline of plankton abundance was largely attributed to the predation of zooplankton on phytoplankton, fish predation on both phytoplankton and zooplankton, and linkages with the decline of water salinity, pH, and the increase of clarity. The decline of plankton abundance was apparently not resulted from long-term change in nutrient concentrations. These conclusions were further supported by that abundances of nano-phytoplankton and micro-phytoplankton oscillated in opposite direction with extremely low density of Cladocera (< 1 individual/L) during the study period. Our conclusions were also supported by the strong interactions between Rotifera and macro-phytoplankton and between nano-phytoplankton and Copepoda, as well as by the describability of the six plankton size groups in a shared trend that was opposite to the trends of water clarity and planktivorous fish stock density. [ABSTRACT FROM AUTHOR]

China has over 1320 freshwater fish species, 877 of which are endemic. In recent decades, over-exploitation and landscape pressures have threatened them and led to a severe aquatic biodiversity crisis. In response, large-scale fishing bans have been promulgated to protect freshwater biodiversity in major Chinese rivers since the early 1980s. Here, we present the historical background and current challenges to the fishing bans. Implementing large-scale fishing bans may help improve China's current freshwater biological resources and biodiversity to some extent. But implementing fishing bans alone is not sufficient to solve the crisis because of shortcomings of the current bans and expanding human pressures in most river basins. Thus, we recommend regulating other anthropogenic pressures, expanding duration and extent of current fishing regulations, establishing a comprehensive monitoring program, and initiating basin-scale ecological rehabilitation. These programs are also needed in other developing countries facing similar biodiversity crises and human pressures. [ABSTRACT FROM AUTHOR]

In our previous work, linear polyelectrolyte cross-linker-bridged hydrogel showed fast gelation within hours, which constrained in-depth deployment of such gels. In the present report, precipitation polymerization of bifunctional VBCTHt monomers in ethanol and acetonitrile generated the nano-gel cross-linkers bearing cyclic sulfonium moieties. The addition of nano-gels cross-linkers to partially hydrolyzed poly(acrylamide) formed covalently cross-linked in situ gels at the temperatures greater than 25 °C. As the morphology of the cross-linker changed from linear form to nano-gel in the state of sphere, the gelation time was controlled from 3 to 40 h. Nano-gel-HPAM system showed three orders of magnitude of delayed gelation while maintaining comparable mechanical integrity in comparison with conventional metallic cross-linked in situ gel, where sulfonium-functionalized nano-gel cross-linkers acting as covalent gelator were utilized for in situ gel formation. The change in cross-linker morphology and bonding nature of the gels dramatically extended gelation time. The mechanics of nano-gel cross-linker-derived covalently cross-linked HPAM in situ gels could be tuned by nano-gel cross-linkers concentration. The viscosity of HPAM and ionic cross-linker gelant had lower viscosity compared to conventional Cr3+-HPAM gel system as confirmed by rheological measurements. The gelant showed excellent salt and pH resistance, rendering it applicable to reservoir conditions. We believe this pioneer work in examination of cross-linker morphology to dictate hydrogel gelation offered the possibility to deploy mechanically tunable gels with delayed gelation for in-depth treatment of reservoir formation to improve fossil energy recovery. [ABSTRACT FROM AUTHOR]

There have been a slew of ready-made methods for the segmentation of univariate time series, but in contrast, there are fewer segmentation methods to satisfy the demand for multivariate time series analysis. It has become a common practice to develop more segmentation methods for multivariate time series by extending segmentation methods of univariate time series. But on the contrary, this paper tries to reduce multivariate time series to a univariate common factor sequence to adapt to the methods for segmentation of univariate time series. First, a common factor sequence is extracted from the multivariate time series as a composite index by a dynamic factor model. Then, three typical search methods including binary segmentation, segment neighborhoods and the pruned exact linear time are applied to the common factor sequence to detect the change points and the segmentation result is considered as the final segmentation result of multivariate time series. The case studies show the applicability and robustness of the proposed approach in hydrometeorological time series segmentation. [ABSTRACT FROM AUTHOR]

Detecting early warning signs of ecosystem degradation in nature reserves requires ultrasensitive biological indicators. We assessed the potential of using multihabitat assessment of benthic algae (growing on submerged vegetation, rocks, and dead trees) to detect early warning signs of nutrient enrichment in nine karstic lakes in Jiuzhaigou Nature Reserve, a World Natural Heritage site in China. Nonmetric multidimensional scaling analysis showed that variability in benthic diatom assemblages among the major habitats within lakes were generally higher than among lakes. Permutational multivariate analysis of variance indicated that epiphytic diatom assemblages dominated by Achnanthidium minutissimum (Kützing) Czarnecki differed significantly from both epilithic and epidendric assemblages. Epilithon and epidendron, both dominated by Delicata delicatula (Kützing) Krammer and Denticula tenuis Kützing, were not significantly different within lakes. Mean Bray-Curtis dissimilarity index values among the three assemblages in each lake were negatively correlated with the tourism-stress index but the correlation was not statistically significant. Increasing homogeneity in benthic diatom assemblages among habitats within a lake may be due to cumulative nutrient enrichment associated with tourism development. Links among tourisms, nutrient enrichment, and dissimilarity in benthic algae among habitats should be viewed with caution until the cause-effect relationships can be confirmed by in situ manipulative experiments. [ABSTRACT FROM AUTHOR]

Identifying and explaining the pattern of how stream fish assemblages vary spatially are basic for the conservation and management of fish species diversity. Although low-head dams may facilitate the native invasions of generalist fishes to headwater streams, few studies have evaluated the impacts of the native invaders on indigenous fish assemblages. In this study, we collected 12 indigenous and 13 native-invasive fish species and measured physical habitats and dam dimensions from 62 impoundments of low-head dams located on headwater streams of the Qingyi River, China. We used linear regression and canonical correspondence analyses to evaluate how habitat and dam variables influenced native-invasive fish assemblages. Our results indicated that invasive fish species richness and abundance were related to elevation and upstream and downstream dam abundances, and their assemblage structures were influenced by substrate heterogeneity, dam height, and upstream and downstream dam abundances. We also used similar analyses to examine how habitat, dam, and invasive fish variables affected indigenous fish assemblages. Our results showed that indigenous fish species richness was correlated with substrate heterogeneity and dam height. However, indigenous fish assemblage structures were not only influenced by dam height, substrate, and downstream dam abundance, but also by invasive fishes. The abundance of one invasive species, Pseudorasbora parva, showed a strong negative influence on indigenous fish assemblages. Our study suggests that the combination of changes in abiotic factors and biotic structure and process following dam-building may determine the indigenous fish assemblages in the impoundments of low-head dams within headwater streams. [ABSTRACT FROM AUTHOR]

Land use change and other human disturbances have significant impacts on physicochemical and biological conditions of stream systems. Meanwhile, linking these disturbances with hydrology and water quality conditions is challenged due to the lack of high-resolution datasets and the selection of modeling techniques that can adequately deal with the complex and nonlinear relationships of natural systems. This study addresses the above concerns by employing a watershed model to obtain stream flow and water quality data and fill a critical gap in data collection. The data were then used to estimate fish index of biological integrity (IBI) within the Saginaw Bay basin in Michigan. Three methods were used in connecting hydrology and water quality variables to fish measures including stepwise linear regression, partial least squares regression, and fuzzy logic. The IBI predictive model developed using fuzzy logic showed the best performance with the R = 0.48. The variables that identified as most correlated to IBI were average annual flow, average annual organic phosphorus, average seasonal nitrite, average seasonal nitrate, and stream gradient. Next, the predictions were extended to pre-settlement (mid-1800s) land use and climate conditions. Results showed overall significantly higher IBI scores under the pre-settlement land use scenario for the entire watershed. However, at the fish sampling locations, there was no significant difference in IBI. Results also showed that including historical climate data have strong influences on stream flow and water quality measures that interactively affect stream health; therefore, should be considered in developing baseline ecological conditions. [ABSTRACT FROM AUTHOR]

Identifying appropriate spatial scales is critically important for assessing health, attributing data, and guiding management actions for rivers. We describe a process for identifying a three-level hierarchy of spatial scales for Michigan rivers. Additionally, we conduct a variance decomposition of fish occurrence, abundance, and assemblage metric data to evaluate how much observed variability can be explained by the three spatial scales as a gage of their utility for water resources and fisheries management. The process involved the development of geographic information system programs, statistical models, modification by experienced biologists, and simplification to meet the needs of policy makers. Altogether, 28,889 reaches, 6,198 multiple-reach segments, and 11 segment classes were identified from Michigan river networks. The segment scale explained the greatest amount of variation in fish abundance and occurrence, followed by segment class, and reach. Segment scale also explained the greatest amount of variation in 13 of the 19 analyzed fish assemblage metrics, with segment class explaining the greatest amount of variation in the other six fish metrics. Segments appear to be a useful spatial scale/unit for measuring and synthesizing information for managing rivers and streams. Additionally, segment classes provide a useful typology for summarizing the numerous segments into a few categories. Reaches are the foundation for the identification of segments and segment classes and thus are integral elements of the overall spatial scale hierarchy despite reaches not explaining significant variation in fish assemblage data. [ABSTRACT FROM AUTHOR]

The impacts of watershed urbanization on streams have been studied worldwide, but are rare in China. We examined relationships among watershed land uses and stream physicochemical and biological attributes, impacts of urbanization on overall stream conditions, and the response pattern of macroinvertebrate assemblage metrics to the percent of impervious area (PIA) of watersheds in the middle section of the Qiantang River, Zhejiang Province, China. Environmental variables and benthic macroinvertebrates of 60 stream sites with varied levels of watershed urban land use were sampled in April, 2010. Spearman correlation analysis showed watershed urbanization levels significantly correlated with increased stream depth, width, and values of conductivity, total nitrogen, ammonia, phosphate, calcium, magnesium, and chemical oxygen demand for the study streams. There was significant difference in total taxa richness, Empheroptera, Plecoptera, and Trichoptera (EPT) taxa richness, and Diptera taxa richness, percentages of individual abundances of EPT, Chironomidae, shredders, filterers, and scrapers, and Shannon-Wiener diversity index between reference streams and urban impacted streams. In contrast, percentages of individual abundances for collectors, oligochaeta, and tolerant taxa, and biotic index were significantly higher in urban impacted than reference streams. All the above metrics were significantly correlated with PIA. The response patterns of total taxa richness, EPT taxa richness, and Shannon-Wiener diversity index followed a drastic decrease at thresholds of 3.6, 3.7, and 5.5% of PIA, respectively. Our findings indicate that stream benthic macroinvertebrate metrics are effective indicators of impacts of watershed urban development, and the PIA-imperviousness thresholds we identified could potentially be used for setting benchmarks for watershed development planning and for prioritizing high valued stream systems for protection and rehabilitation. [ABSTRACT FROM AUTHOR]

essment of lake impairment status and identification of threats’ type and source is essential for protection of intact, enhancement of modified, and restoration of impaired lakes. For regions in which large numbers of lakes occur, such assessment has usually been done for only small fractions of lakes due to resource and time limitation. This study describes a process for assessing lake impairment status and identifying which human disturbances have the greatest impact on each lake for all lakes that are 2 ha or larger in the state of Michigan using readily available, georeferenced natural and human disturbance databases. In-lake indicators of impairment are available for only a small subset of lakes in Michigan. Using statistical relationships between the in-lake indicators and landscape natural and human-induced measures from the subset lakes, we assessed the likely human impairment condition of lakes for which in-lake indicator data were unavailable using landscape natural and human disturbance measures. Approximately 92% of lakes in Michigan were identified as being least to marginally impacted and about 8% were moderately to heavily impacted by landscape human disturbances. Among lakes that were heavily impacted, more inline lakes (92%) were impacted by human disturbances than disconnected (6%) or headwater lakes (2%). More small lakes were impacted than medium to large lakes. For inline lakes, 90% of the heavily impacted lakes were less than 40 ha, 10% were between 40 and 405 ha, and 1% was greater than 405 ha. For disconnected and headwater lakes, all of the heavily impacted lakes were less than 40 ha. Among the anthropogenic disturbances that contributed the most to lake disturbance index scores, nutrient yields and farm animal density affected the highest number of lakes, agricultural land use affected a moderate number of lakes, and point-source pollution and road measures affected least number of lakes. Our process for assessing lake condition represents a significant advantage over other routinely used methods. It permits the evaluation of lake condition across large regions and yields an overall disturbance index that is a physicochemical and biological indicator weighted sum of multiple disturbance factors. The robustness of our approach can be improved with increased availability of high-resolution disturbance datasets. [ABSTRACT FROM AUTHOR]

The identification of disturbance thresholds is important for many aspects of aquatic resource management, including the establishment of regulatory criteria and the identification of stream reference conditions. A number of quantitative or model-based approaches can be used to identify disturbance thresholds, including nonparametric deviance reduction (NDR), piecewise regression (PR), Bayesian changepoint (BCP), quantile piecewise constant (QPC), and quantile piecewise linear (QPL) approaches. These methods differ in their assumptions regarding the nature of the disturbance-response variable relationship, which can make selecting among the approaches difficult for those unfamiliar with the methods. We first provide an overview of each of the aforementioned approaches for identifying disturbance thresholds, including the types of data for which the approaches are intended. We then compare threshold estimates from each of these approaches to evaluate their robustness using both simulated and empirical datasets. We found that most of the approaches were accurate in estimating thresholds for datasets with drastic changes in responses variable at the disturbance threshold. Conversely, only the PR and QPL approaches performed well for datasets with conditional mean or upper boundary changes in response variables at the disturbance threshold. The most robust threshold identification approach appeared to be the QPL approach; this method provided relatively accurate threshold estimates for most of the evaluated datasets. Because accuracy of disturbance threshold estimates can be affected by a number of factors, we recommend that several steps be followed when attempting to identify disturbance thresholds. These steps include plotting and visually inspecting the disturbance-response data, hypothesizing what mechanisms likely generate the observed pattern in the disturbance-response data, and plotting the estimated threshold in relation to the disturbance-response data to ensure the appropriateness of the threshold estimate. [ABSTRACT FROM AUTHOR]

Identification of reference streams and human disturbance gradients are crucial steps in assessing the effects of human disturbances on stream health. We describe a process for identifying reference stream reaches and assessing disturbance gradients using readily available, geo-referenced stream and human disturbance databases. We demonstrate the utility of this process by applying it to wadeable streams in Michigan, USA, and use it to identify which human disturbances have the greatest impact on streams. Approximately 38% of cold-water and 16% of warm-water streams in Michigan were identified as being in least-disturbed condition. Conversely, approximately 3% of cold-water and 4% of warm-water streams were moderately to severely disturbed by landscape human disturbances. Anthropogenic disturbances that had the greatest impact on moderately to severely disturbed streams were nutrient loading and percent urban land use within network watersheds. Our process for assessing stream health represents a significant advantage over other routinely used methods. It uses inter-confluence stream reaches as an assessment unit, permits the evaluation of stream health across large regions, and yields an overall disturbance index that is a weighted sum of multiple disturbance factors. The robustness of our approach is linked to the scale of disturbances that affect a stream; it will be less robust for identifying less degraded or reference streams with localized human disturbances. With improved availability of high-resolution disturbance datasets, this approach will provide a more complete picture of reference stream reaches and factors contributing to degradation of stream health. [ABSTRACT FROM AUTHOR]

We sampled 240 wadeable streams across Wisconsin for different forms of phosphorus and nitrogen, and assemblages of macroinvertebrates and fish to (1) examine how macroinvertebrate and fish measures correlated with the nutrients; (2) quantify relationships between key biological measures and nutrient forms to identify potential threshold levels of nutrients to support nutrient criteria development; and (3) evaluate the importance of nutrients in influencing biological assemblages relative to other physicochemical factors at different spatial scales. Twenty-three of the 35 fish and 18 of the 26 macroinvertebrate measures significantly correlated ( P < 0.05) with at least one nutrient measure. Percentages of carnivorous, intolerant, and omnivorous fishes, index of biotic integrity, and salmonid abundance were fish measures correlated with the most nutrient measures and had the highest correlation coefficients. Percentages of Ephemeroptera–Plecoptera–Trichoptera individuals and taxa, Hilsenhoff biotic index, and mean tolerance value were macroinvertebrate measures that most strongly correlated with the most nutrient measures. Selected biological measures showed clear trends toward degradation as concentrations of phosphorus and nitrogen increased, and some measures showed clear thresholds where biological measures changed drastically with small changes in nutrient concentrations. Our selected environmental factors explained 54% of the variation in the fish assemblages. Of this explained variance, 46% was attributed to catchment and instream habitat, 15% to nutrients, 3% to other water quality measures, and 36% to the interactions among all the environmental variables. Selected environmental factors explained 53% of the variation in macroinvertebrate assemblages. Of this explained variance, 42% was attributed to catchment and instream habitat, 22% to nutrients, 5% to other water quality measures, and 32% to the interactions among all the environmental variables. [ABSTRACT FROM AUTHOR]

A simple and reliable technique to study bacterial chemotaxis in natural aquatic environments is reported. This technique uses the test chemicals in known volumes of semi-solid agar media placed in double layered, highly porous, polyester tubes. Following in situ incubation, bacteria attracted by the test chemicals are enumerated with fluorescence microscopy following acridine orange staining. Studies in an eutrophic reservoir showed that significant numbers of bacteria were attracted to D-glucose and glycine; no significant effects were observed with L-serine, sodium succinate, or sodium chloride. [ABSTRACT FROM AUTHOR]

Key environmental factors and the mechanisms of their influence on the physicochemical habitats and macroinvertebrate communities of streams may vary among ecoregions. We studied the differences in environmental (land use and physicochemical) factors and the mechanisms of their influence on macroinvertebrate assemblages between mountain and lowland ecoregions in central China. We applied generalized linear models to identify key environmental factors that influence macroinvertebrate metrics consisting of taxa richness, Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa, percentages of EPT and intolerant individuals, and the Shannon-Wiener diversity index. Environmental factors and macroinvertebrate metrics significantly differed between the ecoregions. Mountain streams had significantly lower nutrients and %silt, but had twice higher total taxa richness than lowland streams. Watershed land uses were key drivers that influenced the physical habitat in the mountain ecoregion and were the main drivers that influenced both physical and chemical conditions in the lowland ecoregion. Correspondingly, watershed scale land uses, as well as physical and chemical variables, explained more variance in macroinvertebrate metrics than local-scale land uses in both mountain and lowland ecoregions. The overall biological variation was explained better by watershed-scale than by reach-scale land uses, whereas the spatial scale over which land use and physicochemical variables influence streams varied across ecoregions. Our results suggest that better landscape planning should be adopted for watershed management to improve water quality and physical habitat, and thus the conservation and restoration of macroinvertebrate biodiversity. [ABSTRACT FROM AUTHOR]