Flowing Water Systems Research Articles

Changes in the limiting nutrients and dominant phytoplankton communities of three major European rivers: Response to catchment lithologies and human activities

Catchment lithologies and human activities can cause variations in riverine carbon (C), nitrogen (N), and phosphorus (P) loads, and the ratio of these nutrients may affect the primary productivity of rivers and their phytoplankton communities. We conducted a comparative study of biogeochemical variations in three major European rivers—the Rhine, Danube, and Seine—which reveals the impacts of different carbonate outcrops and human impacts (agricultural activities and sewage input) on the changes in the limiting nutrients and phytoplankton community compositions of flowing water systems. N limitation was observed in the Rhine and Danube owing to their low average NO3– loads (4.04–6.45 mg/L). Although the extensive outcrops of carbonate rocks in the Seine catchment result in high average HCO3– concentrations of ∼ 4.68 mmol/L, the elevated inorganic C input did not match the high average NO3– loads (∼19.38 mg/L), driven by intensive agricultural activity and urban sewage input, demonstrating a potential C limitation on productivity. Our results show that the productivity of the Seine River, determined by the chlorophyll-a concentration, was significantly related to the dissolved inorganic carbon (DIC) concentration (coefficient of determination: R2 = 0.68, P < 0.05). Our results demonstrate that changes in DIC content can significantly alter the dominant phytoplankton species in the water column. The high inputs of DIC and aqueous CO2(aq) to the Seine lead to Bacillariophyta proportions that are 3.96–8.81 % and 19.87–22.56 % higher than those of the Rhine and Danube in the wet and dry seasons, respectively. This can be explained by the difference in the efficiency of carbon concentrating mechanisms (CCMs) among phytoplankton species. Therefore, to mitigate river eutrophication and improve the quality of the aquatic environment, we suggest that future water–carbon management in the flowing water systems with abundant nutrients should consider C-limitation alleviation and its potential effect for reducing the abundance of harmful algae.

Highly sensitive resistance spectroscopy technique for online monitoring of biofilm growth on metallic surfaces

Online techniques for monitoring biofilm formation and evolution are limited, especially as regards its application in flowing water systems. This is chiefly due to the absence of efficient non-destructive and non-invasive sensing methods. In this study, a sensitive electrical resistance spectroscopy technique is developed to monitor non-invasively and in real time the growth of biofilms over metallic surfaces inside water flow systems. To this aim, Pseudomonas fluorescens strain is used for biofilm development lasting 72 h in a laboratory-scale test channel of orthogonal cross section. Biofilm development corresponds to a progressively increasing coverage of the metallic surface area up to full coverage and a progressively increasing thickness. Biofilm development is registered by continuous recording of electrical impedance signals (time series). Proper configuration and tuning of the electronics promote the resistive contribution to the signal whereas careful grounding diminishes electrical interferences and yields superb sensing sensitivity. An increase of relative electrical resistance of around 15% is noticed in 72 h flow experiments which is attributed to both an increase of metallic surface area coverage and an increase of biofilm thickness. An independent estimation of these quantities using imaging tools and microscopy analysis, indicates that full coverage of the metallic surface occurs after only 48 h of the flow experiment, whereas biofilm thickness increases gradually along the entire 72 h of the experiment. Cross-examination of electrical signals with biofilm characteristics (metallic surface coverage and biofilm thickness) reveals that, qualitatively speaking, electrical signals are rather more sensitive to metallic surface coverage than biofilm thickness.

Coupling field-scale and watershed models for regulatory modeling of pesticide aquatic exposures in streams.

Estimating exposure in receiving waterbodies is a key step in the regulatory process to evaluate potential ecological risks posed by the use of agricultural pesticides. The United States Environmental Protection Agency (USEPA) currently uses the Variable Volume Water Model (VVWM) to predict environmental concentrations of pesticides in static waterbodies (ponds) that receive edge-of-field runoff inputs from the Pesticide Root Zone Model (PRZM). This regulatory model, however, does not adequately characterize potential pesticide concentrations in flowing water systems (streams and rivers) drained from watershed areas. This study aims at addressing this gap by coupling the regulatory PRZM model with a watershed-level hydrological model, the Soil and Water Assessment Tool (SWAT), to predict pesticide concentrations in flowing water habitats for aquatic organisms. This coupled PRZM-SWAT model was applied in a test watershed (~HUC12), a headwater watershed of Goodwater Creek in Missouri, and simulation results at the outlet of this watershed were compared to daily and near-daily measured streamflow and atrazine concentration data from a decade-long sampling campaign. Overall, the PRZM-SWAT model captured (1) the general magnitude and temporal trend of daily atrazine concentrations, (2) the observed high-end of exposure levels (>3 ppb) of atrazine concentrations, and (3) the 90th centile annual maximum for various exposure durations (1-, 4-, 7-, 21-, and 60-day rolling average), which are important exposure metrics used in assessing the potential ecological risks posed by the application of pesticides. The PRZM-SWAT model is expected to expand the utility of the field-scale regulatory model to include pesticide exposure prediction capability in flowing waterbodies from agricultural watersheds. Integr Environ Assess Manag 2022;18:1678-1693. © 2022 SETAC.

Probing the Stability of Superhydrophobic (SHP) Silane Coating on Anodized Ti Substrate Using Kelvin Probe Force Microscope (KPFM)

The present work aims at probing the stability of superhydrophobic (SHP) silane coating on anodized Ti substrate in different environmental conditions using Kelvin probe force microscope (KPFM) technique. The measurements were carried out for anodized silane-coated SHP Ti samples before and after exposure to UV light and flowing water systems. The KPFM mapping results (surface potential measurements) revealed that the SHP silane coating from anodized Ti surface was partially removed after exposure to the UV light and flowing water system. Moreover, reduction in surface roughness and contact angle was observed after exposure resulting in the conversion of the sample surface from SHP to hydrophobic condition indicating the stability of the coating in the aggressive environments. The results clearly showed that the SHP silane-coated Ti is highly suitable for applications in cooling water system.

A Putative Species Flock in the Diatom GenusGomphonemaEhrenberg (Bacillariophyta: Gomphonemataceae) from Lake Baikal, Russia: Description of Six New Species Similar toG. ventricosumW. Gregory

We describe as new to science six new species of the diatom genus Gomphonema Ehrenberg from Lake Baikal, based on light and scanning electron microscope observations. The six species are morphologically similar to G. ventricosum, a northern European taxon known mostly from Scotland, Scandinavia and other Baltic countries, though it has been recognized also from North America. The six species are similar to G. ventricosum W. Gregory in the structure of the external occlusions over the areolae. The species also have prominent septa and pseudosepta, which distinguishes them from other species of the genus. They are distinguished from one another in the shapes and sizes of the valves. This group of closely related species may correspond to a species flock, a phenomenon in freshwater diatoms that is known from ancient lakes and flowing water systems. Further research is needed to confirm the monophyly of this group, and either support or challenge the idea of them representing a species flock.

Experimental effects of grazers on autotrophic species assemblages across a nitrate gradient in Florida springs

Springs face accelerated degradation of ecosystem structure, namely shifts in autotrophic species assemblages from submerged vascular macrophytes to benthic filamentous algae. Increasing nitrate concentrations have been cited as a primary driver of this shift and numeric nutrient criteria have been developed to address rising nitrate concentrations and restore macrophyte dominance. However, the mechanistic basis of competitive outcomes between algae and macrophytes in these systems remains unresolved. This study assessed how grazing by gastropods influences both algae and macrophyte standing stocks and net production by manipulating gastropod densities in in-situ mesocosms across three levels of nitrate concentrations and autotrophic assemblage composition. The overall effect of grazing was assessed across the range of nitrate concentrations and effect sizes on algae and macrophytes were compared separately within nitrate concentration levels. Results suggest macrophyte success was significantly diminished in the absence of grazers, while the absence of grazers more than tripled the relative standing stock of algal taxa. No consistent pattern of grazer influence was found for net production of either macrophytes or algae. The effect of grazer absence resulted in the largest relative algal standing stocks in low nitrate conditions whereas grazer absence resulted in negative effect sizes on macrophytes standing stocks in low and intermediate nitrate environments. Grazer presence had positive effects on macrophyte standing stocks across all nitrate levels. These results suggest that both nitrate loading reductions and the fostering of healthy populations of grazers would be most effective in the management of these flowing water systems.

Assessment of River Ecosystems and Environmental Flows: Role of Flow Regimes and Physical Habitat Variables

Globally, rivers are under tremendous anthropogenic stress caused by flow fragmentation, land use changes and regulation. Floodplains had been cut out from rivers by embankments due to urban extension and most of the riparian lands in the river basin are under intensive agriculture. There was also widespread water quality degradation due to the industries and municipal wastewater causing a steep decline in the freshwater biodiversity across the world. It was recognised in the literature that the integrity of flowing water systems depended largely on their natural dynamic character which in turn maintained the habitat. Habitat characteristics and presence and absence of particular species suggests that most fishes of flowing water streams are habitat specialists and physical habitat variables including flow regimes played critical roles in the maintenance of their richness. This paper integrated broad environmental flow concepts and defined a new framework for e-flow assessment and implementation based on a review of supportive understanding of variable flow regimes and their benefits to river ecosystems. The main purpose of the framework was to stimulate the emerging discussion on environmental flows prospects in India and other parts of the world. The paper provided an example of the framework applied to River Ganga in India. We end by examining research needs and gaps in our understanding of the role of variable flow regimes and physical habitat variables and their ecological effects on river ecosystems.

The Response of the Spawning of the Four Major Chinese Carps to the Flow Re-Operation of the Three Gorges Reservoir in the Yangtze River, China

The flow regime is a critical factor in the sustained ecological integrity of flowing water systems. The Yangtze River is the most important river in China. The Three Gorges Reservoir greatly changed the flow regime of the Yangtze River, resulting in effects on fish populations, particularly those of the four major Chinese carp (FMCC): black carp, grass carp, silver carp, and bighead carp. Spawning has dramatically decreased since the Three Gorges Reservoir was established in 2003.. Flow re-operation which raising duration time over 3 days and daily discharge change over 1000 m3/s/d were executed in 2012 for 2 times, This study investigated the impacts of flow regulation and re-operation on fish spawning, particularly for the FMCC, and validated the environmental factors that promote spawning of the FMCC. A significant difference in FMCC egg density was observed among five floods, and the FMCC mean egg density after the re-operation was nearly four times that of the regulation flood. A difference in community composition was observed between re-operation and regulation, indicating that the re-operation schedule was sufficient to change the egg community composition. The egg community was significantly correlated with water transparency, change in daily water discharge, and change in daily water level. The better regulation schedule we suggest was the mean daily discharge increase was approximately great than 2000 m3·s-1·d-1 but less than 3050 m3·s-1·d-1, and daily water level increase greater than 0.46 m·d-1.

Uranium contamination of fluvial systems. Mechanisms and processes. Part I : geochemical mobility of uranium along the water path, the Koekemoerspruit (South Africa) as a case study

Tailings deposits from gold- and uranium mining usually contain elevated amounts of radioactive and chemotoxical heavy metals. By seepage dissolved uranium and other contaminants migrate from tailings deposits via groundwater into adjacent fluvial systems. The subsequent transport in streams and rivers is one of the most effective pathways of distributing contaminants throughout the biosphere. In a comparative study of mining areas in Germany, South Africa and Australia mechanisms of non-point stream-contamination and the aqueous transport of uranium were investigated. The study comprises geochemical analyses of samples from various sediment-water systems along the aqueous pathway as well real-time in situ-measurements in the fluvial system itself. In this paper geochemical data of water- and sediment samples from the Koekemoer Spruit as a typical example for a mining affected stream in South Africa - are analysed with respect to possible mechanisms of transport and immobilisation of uranium migrating in solution. Ratios between dissolved and solid phases of uranium for various water-sediment-systems along the aqueous pathway indicated, unexpectedly, significant lower mobility of uranium in stream and channel water than in the groundwater-floodplain system. Correlation of various geochemical parameters suggests co-precipitation of uranium along with calcium-carbonate and iron/manganese-compounds is the main reason for the higher immobilisation rate in the flowing water systems.

Persistent Metal Contamination Limits Lotic Ecosystem Heterotrophic Metabolism after More Than 100 Years of Exposure: A Novel Application of the Resazurin Resorufin Smart Tracer

Persistent stress from anthropogenic metal deposition in lotic ecosystems is a global concern. This long-term selective pressure shapes hyporheic microbial assemblages and influences ecosystem functional integrity. We hypothesized that, even after 100 years of adaptation opportunity, ecosystem function remains inhibited by sediment-associated metal stress and that the Resazurin Resorufin Smart Tracer can be used to quantify this impact. The Resazurin Resorufin Smart Tracer system is applied here in a novel capacity as an indicator of ecosystem function by quantifying ecosystem respiration of microbial communities. Hyporheic microbial communities exposed to differing magnitudes of chronic metal stress were compared to pristine reference sites in controlled column experiments. A Markov chain Monte Carlo technique was developed to solve the inverse smart tracer transport equation to derive community respiration data. Results suggest metals inhibit respiration by 13-30% relative to reference sites and this inhibition is directly related to the level of in situ metal stress. We demonstrate the first application of a hydrologic smart tracer as a functional indicator of ecological integrity within anthropogenically influenced flowing water systems and provide data suggesting resilience is limited in hyporheic ecosystems even after more than a century of microbial adaption to chronic pollutants.

The need for capacity building for biomonitoring of lakes and streams in Asia

AbstractDespite warnings that clean fresh water is becoming increasingly scarce throughout the World, freshwater ecosystems continue to be under threat from economic development. The threat is worse in countries trying to build their economies and/or lack resources to protect their environment. Many economists have warned that economic development that destroys environmental resources is unsustainable. Local expertise needed to evaluate the water quality of lakes and flowing water systems is often missing. Many countries need capacity building programmes to help train young scientists in techniques commonly used to biomonitor aquatic ecosystems in the USA, Europe, Japan and South Korea. Biomonitoring of major groups of organisms can be less costly, relative to sophisticated instrumentation. Further, the presence of even tolerant biological organisms is more dependable than chemical concentrations that can vary continuously. The most effective groups of organisms for biomonitoring include the diatoms, which are often the dominant forms of algae in both lakes and riverine systems, aquatic insects, particularly mayflies, stoneflies and caddisflies, often referred to as the EPT and fishes. Biological methods can be used with an active adaptive management approach that provides guidance for remediation of polluted water systems by studying the levels of degradation or of recovery of ecosystems to or from a more normal state. This approach only can be effective as long the skills exist to understand ecosystems and properly identify lake and river flora and fauna.

Ecology of Symbiotes of Larval Black Flies (Diptera: Simuliidae): Distribution, Diversity, and Scale

Symbioses are major drivers in ecology and evolution. Although nearly omnipresent in flowing waters, they remain poorly studied in these systems. To examine fundamental aspects of the ecology of symbioses in flowing-water systems, we use larval black flies as hosts and various fungi, nematodes, and protists as symbiotes, focusing on aspects of distribution, diversity, and scale. Most symbiotes of larval black flies are considered parasitic, although the dynamic nature of the relationship is becoming apparent for some systems in which it shifts along a continuum involving commensalism, mutualism, and parasitism. Perspective also is moving from a pairwise view of symbiotic associations to a multispecies network of interactions. Distributions of symbiotes are related to scale-dependent processes that influence the hosts and the stream habitats of the hosts; thus, characteristics of streams, as well as hosts, can be useful in predicting spatial patterns of symbiotes. As the taxonomy of symbiotes improves, so too does the understanding of ecological relationships of symbiosis, such as host specificity and patterns of diversity along spatial and temporal scales.

Response of summer chlorophyll concentration to reduced total phosphorus concentration in the Rhine River (Netherlands) and the Sacramento – San Joaquin Delta (California, USA)

Reductions in wastewater loading led to significant declines in mean summer total phosphorus (TP) and chlorophyll concentration (Chl) in two large flowing water systems despite their initially shallow (&lt;2 m) euphotic depth and continually high (&gt;40 mg·m-3) soluble reactive P concentration. In the Rhine River, a gradual 2.7-fold reduction in TP resulted in a 4-fold decline in Chl. In the Sacramento – San Joaquin Delta, an abrupt 1.5-fold reduction in TP led to an equally abrupt 2.6-fold reduction in Chl. Neither response could be attributed to coincidental changes in flow, light, or nitrogen concentration. The slope of the response (Chl:TP) in both systems paralleled the average trajectory calculated using an among-system TP–Chl relationship for a broad cross section of flowing waters. The results suggest that TP was the principal determinant of Chl in both systems and that control of phosphorus loading may be an effective tool for managing eutrophication in other flowing water systems with relatively high (10–100 mg·m-3) soluble reactive P concentrations.

Reducing Harbor Siltation. I: Methodology

This paper describes a decade of research on siltation-reducing measures for harbor basins and the methodology and measuring techniques developed. A classification of harbor systems is made on the basis of siltation mechanisms, i.e. horizontal entrainment by mixing layers, tidal filling, and density currents. This classification distinguishes between harbors in various environments, i.e. stagnant water systems such as shallow lakes, where wind-induced currents prevail, riverine systems, tidal systems, either homogeneously fresh or saline, and estuarine systems with fresh/salt water induced density gradients. Case studies and detailed design studies yielded large reductions in siltation rates of many tens of percents for all harbor basins located in flowing water systems, using a variety of siltation-reducing techniques. These reductions were attained by reducing the exchange flow rates between the harbor and ambient water, and by reducing the sediment concentration of the water entering the basin. In the case of stagnant water systems with very fine, mainly organic matter, a reduction in exchange flow rate cannot be successful, and a reduction in siltation rates can only be achieved through the prevention of dead water zones in the harbor basins. The methodology developed is cost efficient and therefore applicable for large commercial ports as well as small marinas.

Gold tailings as a source of waterborne uranium contamination of streams - the Koekemoerspruit (Klerksdorp goldfield, South Africa) as a case study - part I of III: uranium migration along the aqueous pathway

Tailings deposits from gold and uranium (U) mining in the Witwatersrand basin often contain elevated levels of radioactive and chemo-toxic heavy metals. Through seepage, dissolved U and other metals migrate from tailings deposits via groundwater into adjacent fluvial systems. The subsequent transport through flowing surface water is one of the most effective pathways of distributing contaminants throughout the biosphere. Mechanisms of diffuse stream contamination, as well as the aqueous transportation of U were investigated. In this paper, geochemical data of water and sediment samples from the Koekemoerspruit (a typical example of a stream affected by gold and U mining in South Africa) are analysed with regards to possible transport and immobilisation mechanisms of U migrating in solution. Ratios between dissolved and solid phases of U for various water-sediment-systems along the aqueous pathway indicated, unexpectedly, significantly lower mobility of U in flowing surface water than in the groundwater system of the floodplain. Correlation of various geochemical parameters suggests co-precipitation of U along with calcium carbonate and iron/ manganese-compounds as the main reason for the higher immobilisation rate in the flowing water systems. Owing to redoxinitiated precipitation at the interface of reducing groundwater and oxygenated stream water within the bottom sediments, the latter act as a sink and geochemical barrier for U from groundwater sources. The low retention of U in the highly sorptive floodplain sediments on the other hand is explained by the formation of neutral uranyl-sulphate-complexes, which prevent the positively charged U ion from adsorbing onto negative surfaces of clay minerals and organic substances in the floodplain. Evidence for such complexes are sulphate crusts with extremely high U concentrations, which form on topsoil due to capillary fringe effects in dry periods. Due to their high solubility, these crusts are easily dissolved by rain, resulting in concentration peaks of dissolved U in surface runoff. WaterSA Vol.30 (2) 2004: 219-225

The Western Viceroy butterfly (Nymphalidae: Limenitis archippus obsoleta): an indicator for riparian restoration in the arid southwestern United States?

Life history characteristics of the Western Viceroy (Limenitis archippus obsoleta), an obligate riparian nymphalid butterfly in the desert southwestern United States, are described and related to Colorado River riparian restoration efforts. Riverine disturbance regimes and associated fluvial and hydrological dynamics may provide resources critical to this butterfly. Puddling by adult butterflies may require flood-cleared surfaces and an obligate riparian plant, Gooddings willow, was a larval host plant. This butterfly needs a variety of resources that are only found in close proximity in naturally functioning riparian ecosystems. Habitat heterogeneity required for colony persistence depends largely upon the natural dynamic character of flowing water systems. Because of the links between this butterfly and riparian structure and function it may be a useful indicator for monitoring riparian ecosystem restoration in the area.

The toxicity of zinc to a selected macroinvertebrate, Adenophlebia auriculata (Ephemeroptera, Leptophlebiidae): method development

The South African water quality guidelines for the protection of the aquatic environment are constantly being updated. The Centre for Aquatic Toxicology of the Institute for Water Research, Rhodes University, uses artificial streams and toxicological methods to contribute to the development and refinement of these guidelines. This study involved the use of 96-hour acute toxicity tests, using zinc sulphate as the toxicant, to determine the suitability of Adenophlebia auriculata as a potential indicator species of zinc pollution. As it is known that experimental environments (e.g. still versus flowing water systems) can influence the tolerance of a test species, the experimental system most suited to this species' abiotic requirements was determined. Static and recirculating systems were compared, with LC50 values calculated for the static systems being 91% lower than those calculated for the recirculating systems. The increased sensitivity to the toxicant under static conditions may be due to the animals being additionally stressed by the less favourable static environment. This suggests that recirculating systems are more suited for toxicity tests using this mayfly. Adenophlebia auriculata appears to be tolerant to zinc when compared to zinc LC50 values for other test species in the literature, and may therefore not be a suitable indicator of zinc pollution in an aquatic environment.

Assessing the Impact of Terrestrially Derived Phosphorus on Flowing Water Systems

AbstractRecent efforts to quantify the terrestrial inputs and cycling of P in agricultural systems are allowing management strategies to be developed to minimize the loss of P. While this approach has had clear advantages for standing waters, potential benefits for flowing freshwater systems are more difficult to predict. As a consequence of the unidirectional and dynamic nature of flow in rivers, temporal and spatial separations between the source of P and the point of potential impact arc introduced when considering a whole watershed. The ability to quantify the residence time of P within any particular part of a river system is therefore essential so that the specific contribution of individual P sources to biological demand can be determined. The smaller algal biomass productivity measured in flowing, compared with standing, waters at a similar supply rate of P indicates the need to consider the roles of other watershed factors in modifying the relationship between growth and P supply. The site‐specific nature of responses to P suggests a need to develop a hierarchical classification system where individual river sections can be ranked according to their likely responsiveness to P. The ecoregion concept, combined with stream order, would integrate spatial and temporal aspects of gradient, land use, flow velocity, and water quality. For this to be successful, we must demonstrate a link between perturbations to the terrestrial P cycle, the delivery of P to flowing waters, and a biological impact.

Adaptação do índice de integridade biótica usando a comunidade de peixes para o rio Paraíba do Sul

Uma adaptação do Índice de Integridade Biótica (IIB) utilizando a comunidade de peixes foi realizada para um dos trechos mais críticos do Rio Paraíba do Sul, entre Barra Mansa e Barra do Piraí, visando à obtenção de um padrão de monitoramento biológico que permitisse inferir a qualidade da água de maneira segura, robusta e independente de variações a curto prazo. Um programa de amostragens mensais padronizadas foi realizado, entre março de 1995 e fevereiro de 1996, em quatro locais de coletas (Barra Mansa, Volta Redonda, Pinheiral e Barra do Piraí), todos situados junto à embocadura de riachos tributários, onde foram realizadas as pescarias sistematizadas com idêntico esforço, utilizando rede picaré, tarrafas e peneiras. O Índice de Integridade Biótica (IIB) adaptado foi definido por Karr (1981) como integrador dos fatores ecológicos e ambientais, sendo compreendido por 12 itens relacionados à Composição e Riqueza de Espécies, Composição Trófica e Abundância e Condição dos Peixes. A qualidade da água do rio foi classificada entre Muito Pobre e Razoável, tendo as pontuações do IIB apresentado uma tendência de melhoria crescente ao longo do fluxo do rio, com menores valores em Barra Mansa e maiores em Barra do Piraí, embora tais diferenças não tenham sido estatisticamente significativas (p &gt; 0,01). Sazonalmente, águas de melhor qualidade foram observadas entre março e agosto, e as piores, entre setembro e fevereiro, estas últimas coincidindo com o período de maior pluviosidade, quando maior quantidade de material alóctone é carreado para o rio.

Ecological Responses of Stream Ecosystems Ten Years After Disturbance by Wildfire

Wildfire is a major large-scale disturbance that profoundly influences stream ecosystems over broad spatial and temporal scales. Research has focused primarily on short-term effects, with most data collected within the first few months or years following wildfire. We determined the ecological conditions of 13 streams (10 burned, 3 unburned) 10 years after major fires in Yellowstone National Park (YNP), in order to determine the mid-term responses of stream ecosystems to wildfire. Information from this study is critical to the basic understanding of the role of wildfires in the flowing water systems of wilderness areas and national parks. In addition, this information will be helpful in the formulation of future fire policies and resource management approaches in public forests, wilderness areas, and parks and will provide educational and interpretive information to aid the public and its representatives in better understanding the importance of fire in natural ecosystems. Differences among burned streams in chemical properties were related to local geology and not to the effects of fire. Stream habitat measurements indicated that there was more fine sediment in the burned headwater streams compared to the reference streams and that burned mid-size streams were wider and shallower than the comparable sized reference stream. Benthic macroinvertebrate density was higher and percent Ephemeroptera-Plecoptera­Trichoptera was lower in the burned streams than in the reference. These changes were accompanied by an increase in the proportion of smaller, more vagile taxa, suggesting a shift in community structure from K- to r­ strategists. However, these differences did not exist for taxa richness or biomass, indicating that metabolic compensation accompanied the change in community structure. Mid-term recovery appears to be delayed in YNP streams as a result of increased precipitation and runoff in recent years. These results indicate that significant changes are still occurring in these streams ten years after the fires; these impacts and trends are expected to be even more apparent when the patterns over the whole ten years are examined.