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Wadeable Streams (wadeable + stream)
Selected AbstractsCharacterizing sediment acid volatile sulfide concentrations in European streamsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2007G. Allen Burton Abstract Sediment acid volatile sulfide (AVS) concentrations were measured in wadeable streams of a wide variety of ecoregions of western Europe (84 sites in 10 countries and nine ecoregions) to better understand spatial distribution and ecoregion relationships. Acid volatile sulfide has been shown to be a major factor controlling the bioavailability and toxicity of many common trace metals, such as Cd, Cu, Ni, Pb, and Zn. Sediment characteristics varied widely. The ratio of the sum of the simultaneously extracted metals (SEM) to AVS ranged from 0.03 to 486.59. The ,SEM-AVS ranged from ,40.02 to 17.71 ,mol/g. On a regional scale, sediment characteristics such as dominant parent soil material showed significant trends in AVS distribution and variation by ecoregion. Total Fe and Mn were correlated weakly with SEM concentrations. Three AVS model approaches (i.e., the SEMAVS ratio, SEM-AVS difference, and carbon normalization) were compared at threshold exceedance levels of SEM/AVS > 9, SEM-AVS > 2, and SEM-AVS/foc > 150 ,mol/g organic carbon (OC). Only 4.76% of the sediments exceeded all three AVS thresholds; 22.6% of the sediments exceeded two models; and 13% of the sediments exceeded one model only. Using the SEM:AVS, SEM-AVS, and fraction of organic carbon models, and including site-specific data and regional soil characteristics, ecoregions 1 (Portugal), 3 (Italy), 4 (Switzerland), and 9 (Belgium/Germany) had the highest potential metals toxicity; ecoregions 13 and 8 (Belgium/France) showed the lowest potential toxicity. However, because AVS can vary widely spatially and temporally, these data should not be considered as representative of the sampled ecoregions. The general relationship between AVS levels and sediment characteristics provides some predictive capability for wadeable streams in the European ecoregions. [source] Contamination of fish in streams of the Mid-Atlantic Region: An approach to regional indicator selection and wildlife assessmentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2003James M. Lazorchak Abstract The extent of contamination of fish in the Mid-Atlantic Region was evaluated as part of the U.S. Environmental Protection Agency's Monitoring and Assessment Program's regional assessment in 1993 through 1994. Fish assemblages from wadeable streams were dominated by small, short-lived fishes (e.g., minnows, darters, and sculpins) that were more widely distributed and abundant than large fishes typically chosen for tissue contaminant studies (e.g., trout, black bass, sunfish, common carp). Chemical concentrations in whole-fish homogenates exceeded detection limits for mercury, DDT, and polychlorinated biphenyls (PCBs) in 75 to 100% of the stream length assessed using small fishes and 84 to 100% of the stream length assessed using large fishes. Wildlife values (WVs) representing a threshold for toxic effect were developed to allow examination of the spatial extent of potential risk to piscivorous wildlife. For mercury, DDT, dieldrin, and chlordane, estimates of the regional extent of streams where fish contaminant concentrations exceeded the WVs were greater when based on small fishes than on large fishes. However, within the distribution of stream lengths assessed using small and large fishes, the percentage of stream kilometers exceeding the WVs were quite similar. Our data demonstrate that the greater abundance and distribution of small, short-lived fishes provide greater estimates of regional extent of contamination for first- through third-order streams and can be used for regional assessments of potential exposure and effects in wildlife. [source] Geomorphology and fish assemblages in a Piedmont river basin, U.S.A.FRESHWATER BIOLOGY, Issue 11 2003D. M. Walters Summary 1.,We investigated linkages between fishes and fluvial geomorphology in 31 wadeable streams in the Etowah River basin in northern Georgia, U.S.A. Streams were stratified into three catchment sizes of approximately 15, 50 and 100 km2, and fishes and geomorphology were sampled at the reach scale (i.e. 20,40 times stream width). 2.,Non-metric multidimensional scaling (NMDS) identified 85% of the among-site variation in fish assemblage structure and identified strong patterns in species composition across sites. Assemblages shifted from domination by centrarchids, and other pool species that spawn in fine sediments and have generalised food preferences, to darter-cyprinid-redhorse sucker complexes that inhabit riffles and runs, feed primarily on invertebrates, and spawn on coarser stream beds. 3.,Richness and density were correlated with basin area, a measure of stream size, but species composition was best predicted (i.e. |r| between 0.60,0.82) by reach-level geomorphic variables (stream slope, bed texture, bed mobility and tractive force) that were unrelated to stream size. Stream slope was the dominant factor controlling stream habitat. Low slope streams had smaller bed particles, more fines in riffles, lower tractive force and greater bed mobility compared with high slope streams. 4.,Our results contrast with the ,River Continuum Concept' which argues that stream assemblages vary predictably along stream size gradients. Our findings support the ,Process Domains Concept', which argues that local-scale geomorphic processes determine the stream habitat and disturbance regimes that influence stream communities. [source] Development of an Index of Biotic Integrity for a Southeastern Coastal Plain Watershed, USA,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2007Charles C. Morris Abstract:, This study evaluated biological integrity expectations of fish assemblages in wadeable streams for the Alabama portion of the Choctawhatchee River watershed using a multimetric approach. Thirty-four randomly selected stream sites were sampled in late spring 2001 to calibrate an index of biotic integrity (IBI). Validation data were collected during the spring 2001, and summer and fall of 2003 from disturbed and least-impacted targeted sites (n = 20). Thirty-five candidate metrics were evaluated for their responsiveness to environmental degradation. Twelve metrics were selected to evaluate wadeable streams and four replacement metrics were selected for headwater streams. Scores that ranged from 58 to 60 were considered to be representative of excellent biotic integrity (none found in this study), scores of 48-52 as good integrity (31% of the sites in this study), 40-44 as fair (43%), 28-34 as poor (21%), and 12-22 as very poor (5%). Of the four stream condition categories (urban, cattle, row crop, and least impacted), the IBI scores for urban and cattle sites differed significantly from least-impacted sites. Row crop sites, although not significantly different from least-impacted, tended to have greater variability than the other categories. Lower IBI scores at both urban and cattle sites suggest that the IBI accurately reflects stream impairment in the Choctawhatchee River drainage. [source] Interaction between macroinvertebrates, discharge and physical habitat in upland riversAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue S1 2010Michael J. Dunbar Abstract 1.There is a need to relate changing river flows to ecological response, particularly using methods which do not require extensive new data for water bodies without historical data. This paper describes how local-scale habitat features and changing discharge appear to influence a macroinvertebrate-based biotic index. 2.The study used 87 time-series of river biomonitoring data from upland, wadeable streams with quasi-natural flow regimes across England and Wales. Twenty-seven of the sites were matched to a nearby flow gauging station, and historical, natural flows using a generalized rainfall-runoff model were synthesized for 60 sites. All sites were matched to a River Habitat Survey (RHS) within 1,km. 3.The data were analysed using multilevel linear regression, combining sample- and site-level characteristics as predictors. Common responses were assessed across sites, using the biotic index LIFE (Lotic Invertebrate index for Flow Evaluation), an average of abundance-weighted Flow Groups which indicate the relative preference among taxa for higher velocities with gravel/cobble substrates or slow velocities with finer substrates. The aim was to understand the influence of physical habitat on macroinvertebrate response to antecedent high and low flow magnitude. 4.There was a positive relationship between LIFE score calculated from spring and autumn samples and antecedent high (Q10) and low flows (Q95). The relationship between summer Q10 and autumn LIFE score was steeper than the relationship between winter Q10 and spring LIFE score. Bed and bank resectioning reduced overall LIFE and increased the steepness of the response of LIFE to low (Q95) flow. 5.The models derived may be used to guide environmental flow allocations and to quantify the relative influence of flow and physical habitat change on macroinvertebrate responses. The interaction between resectioning and low flow has particular implications for the conservation of macroinvertebrate taxa with requirements for faster flowing water. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||