756 research outputs found

    Assessing Stream Channel Restoration: The Phased Recovery Framework

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    Channel reconfiguration projects command a large portion of stream restoration resources, while long-term monitoring and research is severely underfunded and rarely implemented. This has led to a limited knowledge base about ecological response and efficacy. Although channel reconfiguration projects are being implemented to restore biological function to lotic systems, the document responses are highly variable and little evidence has shown these projects are reaching their target goals. I predicted the inconsistent response to these projects is the result of disturbance-induced successional processes and catchment-scale water quality impairment. To address how these endogenous and exogenous factors influence stream response to channel reconfiguration, I developed the phased recovery framework and tested it by assessing nine channel reconfiguration sites in western Montana. Each site was composed of a restored reach ranging in age from 1 to 18 years and reference reach representing a minimally disturbed target condition. Five sites were located in unimpaired forested watersheds, while four sites were located in a human-developed watershed experiencing nutrient enrichment, increased fine sediment loads, and elevated stream temperatures. At each site, I assessed macroinvertebrates and associated habitat metrics (physical habitat, canopy cover, stream temperature, dissolved oxygen, and organic matter) and evaluated their response to endogenous and exogenous controls. While physical habitat appears to reach restoration targets immediately following channel reconfiguration, other metrics do not. Channel reconfiguration projects appear to undergo a reorganization phase where organic matter standings stocks and macroinvertebrate densities are significantly reduced for one to two years. Following the reorganization phase, watershed condition drives the recovery trajectory of restored reaches. In unimpaired watersheds, endogenous control, particularly the successional sere of the riparian zone drives ecosystem recovery. Over time, organic matter standing stocks, based on benthic chlorophyll a, become more similar to reference condition (r2 = 0.46, p = 0.05). This corresponds with shredder abundance increasing as projects get older (r2 = 0.78, p = 0.05). Additionally, macroinvertebrate communities become more similar with project age based on Bray-Curtis Dissimilarity (r2 = 0.59, p = 0.13). At impaired sites, oldest restoration reaches were closest to point-source nutrient enrichment and this exogenous control dictated ecosystem recovery. Specifically, benthic chlorophyll a (r2 = 0.98 , p = 0.01) and collector-gatherer abundance (r2 = 0.84 , p = 0.09) increased as sites got older, the opposite trend of unimpaired sites. These results suggest that free of watershed-scale impairment, restoration reaches likely take upwards of two decades to recover to reference condition. If impairment is present, it can exert a strong endogenous control on recovery that overwhelms the influence of channel reconfiguration restoration

    Scaling-up in estuaries: The Feasibility of using small scale results to draw large scale conclusions

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    Estuarine ecosystems are dynamic, heterogeneous ecosystems that are increasingly impacted by human activities, particularly excess nutrient loading and the resulting eutrophication. Much of the descriptive research investigating large-scale eutrophication is performed using field surveys and small-scale, manipulative microcosm experiments. To investigate confounding effects of scale and heterogeneity, we conducted a large-scale field survey of benthic conditions in West Falmouth Harbor (WFH), Cape Cod, Massachusetts, and compared our results to those observed in microcosm studies that utilized sediments and macrofauna from WFH. We used geographic information systems to estimate field condition heterogeneity and design an appropriate sampling strategy, and geostatistical interpolation methods to construct a dataset for the whole estuary based on our disparate sampling stations. Macroinvertebrate distribution was patchy, with somewhat lower densities than were used in experiments. The range of oxygen consumption rates (field 1.1-5.4; microcosm 1.0-9.3 mmol m-2 h-1) and benthic chlorophyll a (field 16-218; microcosm 30-263 mg m-2) were loosely comparable between field and microcosms. Porewater ammonium was higher in the microcosms (field 0-84; microcosm 28-1690 μM), particularly in experimental treatments without animals. The presence of macroinvertebrates in microcosms, especially the sipunculan Phascolopsis gouldii, resulted in better agreement, implying that the degree to which biological conditions approximate reality dictates how closely physico-chemical conditions follow suit. Measures of water depth and seagrass presence compared well to independent surveys, suggesting that sampling methods were adequate. Root mean square errors of the interpolated surfaces were large for most sampled conditions; increasing sampling resolution and adjusting sample collection strategies to account for macroinvertebrate habitat preferences should result in more accurate predictions. Our results have important implications for studies in soft-bottom estuaries, as they validate the use of microcosms to evaluate the relationship between patterns of species distribution and the ensuing system-level processes

    Macrophyte and macroinvertebrate patterns in unimpacted mountain rivers of two European ecoregions

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    The aim of the study was to compare the patterns of development of macrophytes and macroinvertebrates in different types of reference mountain rivers. The study is based on reference river sites surveyed throughout the mountains in Poland and Slovakia in two European ecoregions (9—Central Highlands, 10—The Carpathians). A wide range of environmental variables were estimated, including water chemistry, hydromorphology, geology, and the spatial factor. Based on the Jaccard index, macrophyte and macroinvertebrate variation was confirmed between four mountain and upland river types. It was found that the biological diversification is mainly influenced by geological and associated chemical factors. In the case of macroinvertebrates, additionally, the importance of the spatial factor was revealed (difference between ecoregions). Finally, the habitat preferences of various taxa were identified. It was found that extreme mountain conditions can sometimes distort bioindicative response, as was detected in the case of macroinvertebrates in the highest mountain sites. We concluded that consideration of two groups of organisms enables more comprehensive and reliable monitoring than assessment based on a single group, especially when standard bioindicative methods can be distorted by extreme local conditions

    Database Analysis to Support Nutrient Criteria Development (Phase I)

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    The intent of this publication of the Arkansas Water Resources Center is to provide a location whereby a final report on water research to a funding agency can be archived. The Texas Commission on Environmental Quality (TCEQ) contracted with University of Arkansas researchers for a multiple year project titled “Database Analysis to Support Nutrient Criteria Development”. This publication covers the first of three phases of that project and has maintained the original format of the report as submitted to TCEQ. This report can be cited either as an AWRC publication (see below) or directly as the final report to TCEQ

    Wykorzystanie indeksów biologicznych w ocenie jakości wód rzecznych (rzeka Ruda, Polska)

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    Recognition of the deteriorating conditions of rivers worldwide has called for increased efforts to improve the ecological quality of impacted river systems. This is particularly important in areas that have suffered from a significant impact of human pressure on the ecological status of water. Field studies were conducted in the Ruda River in an area that had undergone anthropogenic disturbances. The objectives of our survey were to test the biological metrics based on benthic macroinvertebrates at four study sites. Spring and autumn surveys of benthic invertebrates indicated that based on the BMWP and BMWP(PL) indices, water quality was higher in comparison with the value of Multimetric index at all of the sites that were studied. Our results revealed that the water quality was higher at the study sites that are located above the dam reservoir based on both the chemical and biological parameters. This study also indicated that both spring and autumn constitute appropriate periods for carrying out monitoring studies. The values of multimeric index indicated the same water quality (except for site 1) in both sampling periods. Anthropogenic transformations of a riverbed influence the flora and fauna and affect the ecological status of rivers

    The Ecological Impacts of Contaminated Sediment from Abandoned Metal Mines

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    Contains public sector information licensed under the Open Government Licence v3.0. The OGL requires that users acknowledge the information provider and/or source of the information with an attribution statement.Pollution from abandoned non-coal (i.e. metal) mines is a serious impediment to rivers meeting the water quality targets set out in River Basin Management Plans. Recent work has identified the mines most likely to be causing a significant environmental impact and hence where efforts to prevent pollution need to be focussed. Yet, it is not clear to what extent rivers, and the animal and plant life they support, are impacted by the legacy of past pollution still bound up in river sediments. Work will be undertaken to reduce toxic metals in mine waters before they enter the river. However, if riverbed sediments are already contaminated and affecting life in rivers, the planned clean-up of mine water sources may not result in recovery of ecological condition. A controlled laboratory experiment was undertaken where river invertebrates (mayfly larvae) from an uncontaminated site were incubated with contaminated riverbed sediment collected downstream of an abandoned metal mine. Concentrations of metals in the tissues of the mayflies increased over the duration of the incubation, particularly those metals that were in high concentrations in the sediment, i.e. cadmium, copper and zinc. As the sediment was the only substantial source of metals in the experiment, it is apparent that the contaminated riverbed sediment was acting as a source of bioavailable metals. It is likely that contaminated sediments, including riverbed sediment, will act as a source of bioavailable metals, at least to benthic organisms, even where mine drainage water is treated to reduce metal concentrations. Metal toxicity occurs when the rate of metal uptake into an organism exceeds the combined rates of excretion and physiological detoxification. Current tests of metal toxicity on biota typically do not match in scale (temporal, spatial and taxonomic range) with assessments of ecological quality undertaken for management, which raises questions regarding the adequacy of environmental limits based on laboratory testing. Existing data were compiled describing geochemistry of riverbed sediment and the Biological Quality Elements invertebrates, diatoms, macrophytes and fish, collected by the regulatory authorities to assess the condition of rivers. As toxic effects of trace metals were not expected at low concentrations, the biological response to sediment metal concentration was determined using a threshold model. Thresholds were found for biotic metrics based on species richness, but other metrics (diatom EQR, macrophyte EQR and invertebrate ASPT) displayed implausible positive relationships with sediment metal concentrations and should not be relied upon for classification of ecological status in waterbodies affected by mining. New data were collected from 20 spatially-independent river catchments in areas affected by metal mine facilities, including samples of the macroinvertebrate community, bioavailability of metals (assessed as metal concentrations in the body tissue of tolerant taxa), and sediment metal concentrations. There were strong correlations between sediment metal concentrations and measured bioavailability, particularly for copper and lead. Measurements of bioavailable metals were related to changes in taxon richness in the invertebrate samples. The data were used to develop a new biotic index (MetTol), which can be used to assess the extent of ecological damage from metal contamination using standard invertebrate monitoring data, and to construct dose response curves based on species sensitivities. A number of approaches were used to establish tolerable limits for sediment metal concentrations based on ecological data, and the results compared with existing Canadian sediment quality guidelines. The limits for copper derived from ecological data were most consistent with existing sediment guidelines. The limits for other metals (silver, arsenic, cadmium, nickel, lead and zinc) derived from ecological data were up to an order of magnitude above the Canadian interim sediment quality guidelines. These existing guidelines, based on toxicological data, may be too precautionary, and we suggest that guideline sediment concentrations based on ecological data may provide a more appropriate level of protection for the environment
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