Freshwater invertebrate conservation faces 5 important challenges. First, ˜10,000 species of freshwater invertebrates around the world may already be extinct or imperiled. Second, human pressures on freshwater resources are intense and will increase in the coming decades, putting yet more species at risk. Third, scientific knowledge about freshwater invertebrates, although substantial and useful for many groups, is far less than for the vertebrates for which much of contemporary conservation biology was designed. Even the best-known freshwater invertebrates that have achieved legal protection are perhaps 1% as well studied as the typical vertebrate. Fourth, because freshwater ecosystems are downhill from and embedded in their watersheds, freshwater conservation usually has to manage entire watersheds rather than small local sites where imperiled species occur. Fifth, society spends only modest amounts of money for freshwater invertebrate conservation. The median expenditure in Fiscal Year 2003 for freshwater invertebrate species on the US Endangered Species List was only US$24,000, and only a small minority of imperiled species is listed and receives even this modest attention. Considering these serious challenges, I believe that we need to think deliberately about the best approaches for conserving freshwater invertebrate biodiversity. The best solution may be to move away from a species-based approach that is largely derived from a terrestrial model towards broader, regional approaches that try to satisfy legitimate human needs for fresh water while preserving as much biodiversity as possible.

Application of a hydrogeologic computer model underscored the importance of geomorphic controls on groundwater and surface-water flow dynamics in the Nyack Floodplain, a montane alluvial floodplain in Montana, USA. The model represented the floodplain as a hierarchy of geomorphic patches, which facilitated analysis of model results using independent (predictor) variables at multiple scales. The analyses revealed that geomorphic structures at various spatial scales interact with the flow regime to influence the direction, magnitude, and stability of hyporheic flow within individual floodplain patches. Specifically: 1) the hydrologic flow network within the hyporheic zone is more responsive to seasonal changes in river discharge if floodplain topography is complex and aquifer properties are heterogeneous, 2) simplification of internal patch structure across the floodplain eliminates the influence of fine-scale geomorphic structures on the stability of groundwater flow paths, although the influence of patch context remains, and 3) incremental changes in river discharge can abruptly and substantially restructure the relationship between river discharge and groundwater flow patterns when events such as inundation of previously dry flood channels occur on the floodplain. We believe that ecological theories of biodiversity can be used to understand interactions among geomorphic variation, hydrologic dynamics, and the maintenance of biodiversity in the hyporheic zone if abrupt reorganization and other variations in groundwater flow paths act as disturbances to hyporheic communities. From this perspective, we used model results to develop 4 hypotheses describing the potential for causal linkages among floodplain geomorphology, hyporheic flow-path variation, hyporheic habitat diversity/stability, and hyporheic community diversity.

Release of P from lake sediments may account for a significant portion of a lake's total P (TP) load. Previous studies using sediment cores showed that ˜65% of the total P load entering Spring Lake, Michigan, came from the sediments, and that an alum concentration of 24 mg Al/L effectively inactivated P release in experimental sediment-core tubes. In 2004, we studied the influence of alum concentration and sediment resuspension on P release rates from the sediments. Based on laboratory incubations using alum concentrations of 0, 5, 10, 15, 20, and 25 mg/L, we determined that P release rates at alum concentrations ≥15 mg/L were no different than at release rates at concentrations of 25 mg/L. Resuspension of sediments substantially increased TP concentrations, even at high alum concentrations, but total soluble P concentrations remained low in the water when alum was present. Alum application may be an effective tool to reduce P flux from sediments in shallow lakes, but external P load reduction must accompany alum application to address the long-term impacts associated with cultural eutrophication.

Secondary and tertiary wastewater treatment is common in developed countries, but little is known about the responses of lotic ecosystems to contemporary wastewater treatment plant (WWTP) discharge. We examined the effects of WWTP discharge on various ecosystem components and functions of 2 morphologically and chemically impacted lowland streams near Berlin, Germany. We sampled one reach upstream and one reach downstream of a WWTP in each stream during each of 5 sampling campaigns. Discharge of treated wastewater resulted in increased concentrations of total organic C, total N, and total P in the sediments and in elevated macrophyte and benthic invertebrate biomasses. However, adverse effects of the WWTPs on the benthic invertebrate communities were small compared to effects reported in previous studies. This difference was a result of the higher purification efficiency of modern WWTPs, but also of significant structural degradation and eutrophication of the streams that already had impoverished the invertebrate community upstream of the WWTPs. Whole-stream community respiration (CR₂₄) and gross primary production (GPP) were both enhanced by WWTP discharge. WWTP discharge generally caused diminished NH₄- and PO₄-uptake efficiencies, but did not necessarily lead to diminished NO₃-uptake efficiencies of streams. Increases in areal NO₃-uptake rates caused by the discharge of a large municipal WWTP were high enough to result in increased load-specific NO₃-uptake efficiencies. Our study shows that the effects of present-day WWTPs on stream ecosystem functioning clearly differ from the former impacts of poorly treated wastewater. Present-day WWTP discharges mainly cause eutrophication and subsequent side effects and low nutrient-retention efficiencies relative to the high nutrient concentrations and loads of impacted streams. Our results highlight the need for efficient tertiary treatment of wastewater and for the refinement of agricultural practices to reduce diffuse nutrient loadings. We found evidence that even efficiently treated wastewater can have extensive effects on stream ecosystem structure and function. Therefore, adequate dilution rates always should be considered when routing treated wastewater through lotic networks. Our findings on the response of key ecosystem variables to present-day WWTP loading underline the importance of scientifically based stream management.

Biological indicators often are used to assess and manage water quality in anthropogenically altered stream systems. Leaf breakdown has the potential to be a good indicator of stream integrity because it integrates a variety of biological, chemical, and physical conditions. Red maple (Acer rubrum L.) leaf breakdown rates were measured along a gradient of agricultural land use in southern Appalachian streams to assess the use of leaf breakdown rates as a measure of stream integrity. Landuse categories included forested, light agriculture, moderate agriculture, and heavy agriculture. Leaf breakdown rates were related to landuse category but did not differ significantly among landuse categories. Nutrient concentration, temperature, and sedimentation increased, and dissolved O₂ decreased along the landuse gradient from forest to heavy agriculture. Macroinvertebrate richness, macroinvertebrate density, and shredder density were the only significant predictors of leaf breakdown rates. We conclude that leaf breakdown rates may not be a useful indicator of stream integrity because of the confounding effects that agricultural land use has on breakdown rates.

The objectives of our study were to assess leaf-litter breakdown in 3 streams in 3 climates and to determine the contributions of associated microbial and invertebrate communities to the process. We incubated leaves of Alnus glutinosa in 1 stream in each of 3 climate zones: temperate (mountains of Central Portugal), Mediterranean (South Portugal), and tropical Cerrado (Minas Gerais, Brazil). Leaf-litter breakdown rates (/d) were faster in temperate (k = 0.023–0.017) than in tropical (k = 0.014) or Mediterranean (k = 0.014–0.009) streams. Leaf-litter breakdown rates (/degree day) also were higher in the temperate stream (k = 0.0018–0.0032) and similar between the other 2 streams (k = 0.008–0.0012). Colonization of leaves by aquatic hyphomycetes was faster in the temperate stream (maximum = 421 μg ergosterol/g of leaf by day 24) than in the tropical Cerrado or Mediterranean streams. However, peak ergosterol content was highest in the tropical Cerrado stream (573 μg/g on day 75). Ergosterol content was lowest in the Mediterranean stream (maximum = 341 μg/g on day 7). Total microbial biomass (as ATP) was higher in the tropical Cerrado stream (maximum = 531 nmoles/g on day 75) than in the Mediterranean (maximum = 108 nmoles/g on day 92) and temperate (maximum = 93 nmoles/g on day 7) streams. These results suggest either that not all microorganisms associated with leaves were involved in leaf-litter breakdown or that other less efficient microorganisms than fungi were involved in leaf-litter breakdown in the tropical stream. Leaves exposed to invertebrates (coarse-mesh bags) decomposed significantly faster than leaves protected from invertebrate feeding (fine-mesh bags) only in the temperate stream. This result suggests that invertebrates were important mediators of leaf-litter breakdown only in the temperate stream. A larger proportion of invertebrates recovered from decomposing leaves were shredders in the temperate stream (nearly 5%) than in the Mediterranean (1%) and tropical Cerrado (0%) streams. Leaf-litter processing rates increased with discharge and NO₃ concentration in the water. Our results suggest that the positive effect of temperature on breakdown rates of allochthonous organic matter in streams can be overridden by nutrient content in the water and the presence of invertebrate shredders.

We investigated whether suburbanization influenced the physical and biological characteristics of ten 3^rd-or 4^th-order streams that drain historically agricultural watersheds in the southern Appalachians near Asheville, North Carolina. Five watersheds had areas of recent suburban development proximal to stream sites, and 5 watersheds were not currently undergoing suburban development. We estimated 5 hydrological, 10 geomorphological, 6 erosional, and 3 depositional (i.e., substrate) variables, and 13 fish and 8 macroinvertebrate metrics in the study sites. We used Student's t-tests and multivariate analysis of variance to compare the 45 variables between sites in agricultural and suburban watersheds. We used Detrended Correspondence Analysis (DCA) to detect subtle differences in taxonomic composition and abundance among watersheds. Stormflow total suspended solids were significantly lower and substrate inorganic matter content was significantly higher in streams influenced by suburban development. Fish taxa richness and the density of nonguarding fishes were significantly higher in sites in suburban watersheds than in sites in agricultural watersheds. No other fish or macroinvertebrate metric differed with respect to watershed land use, but ordination of sites by fish and macroinvertebrate species abundance suggested that biotic assemblages at sites in suburban watersheds were distinct from those at sites in agricultural watersheds. Therefore, some taxa may have been influenced by suburban development. Our results suggest that watershed hydrology, sediment delivery, and sediment composition might be important factors influencing biota in streams draining agricultural vs suburban watersheds. Biological assemblages in streams differed structurally with respect to watershed land use, but streams did not appear to be otherwise influenced by suburban development. We conclude that suburbanization near historically agricultural southern Appalachian streams induces subtle changes to inorganic sediment dynamics, substrate composition, and fish and macroinvertebrate assemblage structure.

Terminal-restriction fragment length polymorphism (T-RFLP) is a DNA-based technique used to examine microbial community structure. We used this technique to examine variability in microbial community structure in 3 pools and a riffle in a semipermanent stream that becomes a chain of pools during the summer. We examined microbial communities under 3 hydrological conditions: predrought (all sites inundated), drought (all sediments dried for ≥2 mo), and rewet (1 mo after inundation). We used nonmetric multidimensional scaling to ordinate microbial communities and analysis of similarity to test whether communities differed among sites and whether community structure within sites changed in response to drought and rewetting. Microbial communities within sites differed with respect to hydrological condition, with most within-site variability occurring within the riffle section of the stream. Sediment drying significantly changed the microbial community structure at all sites. One month after rewetting at all sites, the microbial communities had not returned to their predrought structures and were significantly different from the predrought and drought microbial communities. Within-site variability in microbial community structure was much lower after the drought than before the drought. T-RFLP proved to be a powerful method for resolving microbial community structure, and its application helped address our limited understanding of microbial community dynamics.

Quantifying periphyton (attached algal) contributions to autotrophic production in lakes is confounded by properties of substratum that affect community biomass (as chlorophyll content) and productivity. We compared chlorophyll content and productivity of natural algal communities (phytoplankton, epipelon, epilithon, epixylon, and epiphyton) experiencing high (>10%) incident radiation in lakes in the US, Greenland, and Quebec, Canada. Chlorophyll content and productivity differed significantly among regions, but they also differed consistently among communities independent of region. Chlorophyll content of periphyton on hard substrata (rocks and wood) was positively related to water-column total P (TP), whereas chlorophyll content of algae on sediment (epipelon) and TP were not significantly related. Chlorophyll content was up to 100× higher on sediments than on hard substrata. Within regions, chlorophyll-specific primary productivity was highest for phytoplankton and lowest for epipelon. Periphyton on hard substrata and on macrophytes (epiphyton) had similar rates of chlorophyll-specific productivity that were intermediate to those of epipelon and phytoplankton. Area-specific productivity of epipelon was 5 to 10× higher than area-specific productivity of periphyton on hard substrata. This broad geographic comparison indicates that, in low to moderately productive lakes under high-light conditions, algal communities have predictable differences in area-specific and chlorophyll-specific productivity based on substratum. As such, chlorophyll alone is an inadequate predictor of the relative contributions of different algal communities to total primary production. Our results highlight the importance of the relative abundance and spatial distributions of substrata in determining the role of the littoral zones in nutrient and energy cycles in lakes.

The invasive North American amphipod Gammarus tigrinus is successfully established in Lough Neagh, Northern Ireland. Gammarus tigrinus is increasingly recognized as having significant predatory impacts on macroinverebrates, contrary to the accepted functional feeding group status of Gammarus species. The native opossum shrimp Mysis relicta overlaps in habitat use with G. tigrinus. However, its interaction with benthic macroinvertebrates is rarely appreciated. Mutual predatory interactions between G. tigrinus and M. relicta were assessed in a series of laboratory experiments. Gammarus tigrinus actively preyed on adult and juvenile M. relicta at a range of spatial scales. Females and recently molted M. relicta were particularly vulnerable to predation. Mysis relicta did not prey on adult G. tigrinus, but rapidly eliminated juvenile G. tigrinus in microcosms. Changes in dissolved O₂ saturation did not alter the predatory interaction between these species. Microhabitat use by M. relicta was altered in the presence of G. tigrinus, and the presence of G. tigrinus facilitated fish predation on M. relicta. A balance of mutual predatory pressure between these invasive and native species may explain their coexistence. Both species are likely to be strongly interactive with other macroinvertebrates in both native and invasive ranges.

Temporal patterns of abundance, biomass, and production of 3 populations of Caridina cantonensis (Atyidae) and 1 population of C. serrata were studied in 2 unshaded and 2 shaded Hong Kong streams. Monthly quantitative sampling was done in each of the 4 study sites over 2 y (April 2000–March 2002). Secondary production of C. cantonensis, estimated by the size-frequency method (P_SF) and averaged over the study period, ranged from 1665 to 2274 mg ash-free dry mass (AFDM) m⁻² y⁻¹ according to site; P_SF of C. serrata (810 mg AFDM m⁻² y⁻¹) was <½ that of C. cantonensis. Total shrimp production was greater at the 2 unshaded sites during both years. Interyear differences in P_SF were not significant, but shrimp production was 10 to 83% higher during the dry season than the wet season, most notably in the 2 unshaded streams (≥40% higher). This seasonal difference probably was caused by mortality from spates associated with the summer monsoon. Production estimated by the instantaneous growth method showed the same trends as P_SF, but yielded values 26 to 57% lower. Annual P_SF/biomass ratios ranged from 2.02 to 3.89 and were correlated with cohort-specific growth rates of shrimp populations; neither parameter was directly related to the extent of shading. Instantaneous growth rates of Caridina spp. estimated from caged shrimps at each of the 4 study sites did not differ between years. Instantaneous growth rates in cages appeared correlated with cohort-specific growth rates of field populations, suggesting that the intra- and interspecific variations in P_SF of Hong Kong atyids represent genuine ecological differences rather than methodological artifacts. Production of Caridina spp. was considerably higher than has been reported for other macroinvertebrate taxa in Hong Kong streams, constituting ˜10% of total macroinvertebrate production for these systems and demonstrating the importance of atyid shrimps in tropical stream food webs.

Allozymes were used to examine population genetic structure and species boundaries in the clonal, obligately parthenogenetic Centroptilum triangulifer and its sexual sister species Centroptilum alamance from 3 sites in Pennsylvania and 1 site in North Carolina, USA. Genotype frequencies in field populations of C. triangulifer showed numerous departures from Hardy–Weinberg expectations (mostly heterozygote excesses) and significant linkage disequilibrium at most testable locus combinations, as expected for a clonal parthenogen. A total of 51 distinct clones of C. triangulifer was identified, some of which were found at multiple sites (separated by >700 km in one case). Each stream contained from 7 to 25 clones and clonal frequencies at a given site varied greatly over time. Allelic patterns in laboratory hybrids suggest that parthenogenesis in C. triangulifer is diploid and automictic, and that crossing over is suppressed. In contrast, C. alamance populations had only a few Hardy–Weinberg departures (all heterzygote deficiences) and little or no linkage disequilibrium. No published work provides characters to distinguish the 2 species, but our data support retention of specific status for C. triangulifer and C. alamance because: 1) consistent, fixed allelic differences were found over a broad geographic area (>700 km) with no evidence of introgression despite co-occurrence (sympatry) in the same stream, 2) laboratory hybridization experiments demonstrated the existence of postzygotic barriers to gene flow between the species, and 3) measures of both interspecific and intraspecific genetic similarity were comparable to those found between other mayfly species. Phylogenetic analysis of the genetic data suggests speciation preceded the transition to obligate parthenogenetic reproduction in C. triangulifer. Morphological examination of genetically identified specimens enabled us to describe subtle but consistent differences that can be used to distinguish the species. Thus, what initially appeared to be single populations with skewed sex ratios (7, 11, and 24% male) at 3 of our study sites was, in fact, 2 populations at each site—1 exclusively female (C. triangulifer) and the other a normal, sexual (1:1 sex ratio) population (C. alamance). A similar approach, combining detailed genetic and breeding experiments with close morphological study, could help resolve taxonomic problems in some of the numerous other bisexual/parthenogenetic mayfly taxa.

The duration and timing of egg development is crucial to the survival of invertebrates in glacier-fed rivers. The relationship between egg development and environmental conditions was investigated in 3 mayfly species, Baetis alpinus, Rhithrogena nivata, and Ecdyonurus picteti, in an alpine glacier-fed alluvial system. Field-collected eggs were reared in the laboratory at temperatures representing field conditions (1.5, 3, 5, and 7°C). Egg-incubation period and degree-days demand (DD) were determined, and hatching in the field was predicted from field temperature records. Egg development and temperature relationships for B. alpinus and R. nivata were documented for the first time. Baetis alpinus had synchronous egg development and high hatching success. Faster development in warmer habitats enabled it to hatch during favorable autumnal conditions. Ecdyonurus picteti had a very long development time that decreased slightly at higher temperatures. However, the variation in DD was considerable. The observed long and delayed hatching would favor successful development in unpredictable habitats at the low temperatures experienced in these glacial conditions. Rhithrogena nivata, one of the most extreme cold-adapted mayfly species, had a long egg incubation period, and success in development largely depended on the timing of hatching and discharge conditions. This species could exploit extremely unstable and cold habitats where other species are limited by low water temperatures.

Chironomid midges are abundant and important components of freshwater communities, but estimating their production is problematic because of taxonomic difficulties, short generation times, and overlapping cohorts. We measured growth rates of nontanypodine chironomid larvae from a 3^rd-order stream in southern Illinois, USA, at different temperatures to estimate assemblage-level production using the instantaneous growth method. We collected Chironomini, Tanytarsini, and Orthocladiinae larvae, separated them into small (0–3.9 mm), medium (4–7.9 mm), and large (8–12 mm) size classes, and then reared larvae in a controlled environment for 3 to 7 d at temperatures ranging from 5 to 28°C. We measured lengths of individual larvae before and after each trial and estimated biomass using a length–mass regression. Instantaneous growth rates (g) across all size classes ranged from 0.008 mg mg⁻¹ d⁻¹ at 5°C to 0.24 mg mg⁻¹ d⁻¹ at 22°C. Instantaneous growth rates of small larvae increased linearly with temperature between 5 and 22°C (r² = 0.99, p = 0.0003). Instantaneous growth rates of medium and large larvae also appeared to increase linearly with temperature (medium: 5–22°C, large: 5–25°C), although power functions explained a greater proportion of the variance than linear functions (medium: r² = 0.96, p = 0.004, large: r² = 0.77, p = 0.05). We applied these models to data from monthly samples from the same stream and obtained an annual habitat-weighted production estimate of 4.2 g ash-free dry mass m⁻² y⁻¹ and an annual production to biomass ratio of 26. Application of 2 other assemblage-level chironomid growth models developed for headwater streams in the southern Appalachians yielded much different production estimates, illustrating the risks of applying these types of models to systems with different temperature regimes, taxonomic composition, or size spectra. Our temperature-specific models will enable more accurate estimates of chironomid production in central USA streams with thermal regimes and larval midge assemblages similar to those in Big Creek.

Stream ecologists often use enclosure experiments to investigate predator–prey interactions and competition within and among fish species. The design of enclosures, manipulation of species densities, and method of replication may influence experimental results. We designed an experiment with enclosure cages (1 m², 6-mm mesh) to examine the relative influence of fish size, density, and prey availability on growth of brown trout (Salmo trutta), brook trout (Salvelinus fontinalis), and slimy sculpin (Cottus cognatus) within enclosures in Valley Creek, Minnesota. In addition, we examined water flow and invertebrate drift entering enclosures and in open riffles to investigate whether enclosures reduced the supply of invertebrate prey. Growth of small (age-0) brook and brown trout was not influenced by fish density, but growth of larger (age-1) trout generally decreased as density increased. Sculpin growth was not related to fish size or density, but increased with mean size of invertebrates in the drift. Enclosures reduced water flow and tended to reduce invertebrate drift rate, although total drift rate (ind./min), total drift density (ind./m³), and mean size of invertebrates were not significantly different inside enclosures compared to adjacent stream riffles. Enclosures had no effect on drift rate or size of Gammarus pseudolimnaeus, the main prey item for trout and sculpin in Valley Creek. Overall, our analyses indicated that reductions of prey availability by enclosures did not influence fish growth. Trout growth may have been limited at larger sizes and densities because of increased activity costs of establishing and defending territories, whereas sculpin growth was related to availability of large prey, a factor not influenced by enclosures.

We sampled pupal exuviae in 39 Mediterranean stream sites, situated in 2 mountain regions in the Betic ranges (southern Spain) to test the value of chironomid species assemblages for stream classification and water-quality evaluation. Downstream reaches of these streams are organically polluted to different extents, but the headwaters are protected, providing reference sites for comparison with impaired sites in the mid elevations. A priori classification of sites was done using 7 physiographical and geological variables to differentiate stream types independently of human influence. A posteriori classification and ordination analyses of sites were done on an environmental matrix of 28 variables and a biotic matrix of 204 chironomid species. Regional-scale factors played a more important role than reach-scale factors (i.e., water chemistry) in structuring chironomid assemblages. However, within each region, reach-scale factors such as thermal regime and variables related to water-quality impairment also exerted important influences on chironomid assemblage structure. The indicator value of chironomid species, obtained by comparing reference and impaired sites in the same stream type, showed that 6 species clearly had a positive response to water-quality impairment. This response does not appear to be dependent upon stream type or regional setting, either in the studied area or in other fluvial ecosystems of Western Europe. Moreover, these chironomid species seemed to be distributed along a wide gradient of water-quality impairment, suggesting their potential for evaluating a great range of water-quality degradation.

Salinization has been disturbing increasing numbers of inland waterways, and new analytical tools are needed to survey water quality and to assess the impact of salinization. Researchers have developed new protocols that reduce the number and type of samples required to reduce the cost of existing assessment methods. Our study contributes to this effort with the primary objective of identifying a single, unique river-bottom substrate that could be sampled to detect the impact of rising salinity on macroinvertebrate assemblages. We hoped to define a new concept of sentinel substrate, a substrate with an invertebrate assemblage that would signal an environmental impact (in this case increasing salinity) and that could be used at the site scale to assess that impact. We worked on the Meurthe River, which presents a significant salinity gradient (from 0.2 to 2.6 g/L) over a 19-km section of river in which all other physicochemical variables remain stable. We sampled substrates present at each of 4 sites along the salinity gradient in 2002 and described the effects of rising salinity on the structure (richness, diversity, and dominance) of the macroinvertebrate assemblage in each substrate type. Only the assemblage in pebbles adequately reflected site-level responses. Moreover, only assemblages in pebbles satisfied important criteria such as widespread availability, low variability among seasons, and high invertebrate diversity.

The ability of 2 Rapid Bioassessment Protocols (RBPs) to assess stream water quality was compared in 2 Mediterranean-climate regions. The most commonly used RBPs in South Africa (SA-protocol) and the Iberian Peninsula (IB-protocol) are both multihabitat, field-based methods that use macroinvertebrates. Both methods use preassigned sensitivity weightings to calculate metrics and biotic indices. The SA- and IB-protocols differ with respect to sampling equipment (mesh size: 1000 μm vs 250–300 μm, respectively), segregation of habitats (substrate vs flow-type), and sampling and sorting procedures (variable time and intensity). Sampling was undertaken at 6 sites in South Africa and 5 sites in the Iberian Peninsula. Forty-four and 51 macroinvertebrate families were recorded in South Africa and the Iberian Peninsula, respectively; 77.3% of South African families and 74.5% of Iberian Peninsula families were found using both protocols. Estimates of community similarity compared between the 2 protocols were >60% similar among sites in South Africa and >54% similar among sites in the Iberian Peninsula (Bray–Curtis similarity), and no significant differences were found between protocols (Multiresponse Permutation Procedure). Ordination based on Non-metric Multidimensional Scaling grouped macroinvertebrate samples on the basis of site rather than protocol. Biotic indices generated with the 2 protocols at each site did not differ. Thus, both RBPs produced equivalent results, and both were able to distinguish between biotic communities (mountain streams vs foothills) and detect water-quality impairment, regardless of differences in sampling equipment, segregation of habitats, and sampling and sorting procedures. Our results indicate that sampling a single habitat may be sufficient for assessing water quality, but a multihabitat approach to sampling is recommended where intrinsic variability of macroinvertebrate assemblages is high (e.g., in undisturbed sites in regions with Mediterranean climates). The RBP of choice should depend on whether the objective is routine biomonitoring of water quality or autecological or faunistic studies.

One of the dilemmas in designing any large-scale macroinvertebrate bioassessment is deciding where to sample within streams. Streams contain a wide variety of habitats with varying macroinvertebrate assemblages, yet consistency in sampling protocol is needed to interpret results across sites in a region. The Environmental Monitoring and Assessment Program (EMAP) conducted large regional probability surveys in the mid-Atlantic (1993–1998) and the western US (2000–2001). In these surveys, 2 macroinvertebrate sample types were collected at each site: pool and riffle in the mid-Atlantic region, and reachwide and riffle in the western US. We analyzed data from sites where both types of samples had been collected (206 mid-Atlantic and 293 western US sites) to examine the effects of sample type on typical metric and multivariate analyses done in bioassessments. Sample types differed in terms of taxon richness measures and assemblage composition, and differences were more pronounced between mid-Atlantic riffle and pool samples than between western US reachwide and riffle samples. Nonetheless, sample-type differences did not obscure the overall pattern in ordination analyses, nor did they influence detection of important environmental gradients. In addition, bioassessments based on Ephemeroptera, Plecoptera, and Trichoptera taxon richness showed that regional assessments differed little with sample type. Our analyses indicate that typical bioassessment methods are relatively robust with respect to sample type in regional surveys. Reachwide sampling could be used with little risk to the quality of assessments in surveys covering large geographic areas where a single targeted habitat may not occur at all sites. Reachwide sampling is also easy to apply consistently at most sites and requires approximately the same effort and cost as single-habitat sampling.

Regional bioassessment programs of states, various federal agencies, and other governmental and private groups often use different methods to collect and analyze stream invertebrate samples. This lack of uniformity has created concern and confusion over the comparability of disparate sources of data, but few studies have attempted to evaluate differences in performance between methods or to reconcile the results produced from different methods. We conducted concurrent sampling at 40 sites in the eastern Sierra Nevada of California using 3 bioassessment methods to obtain directly comparable data sets. The riffle-based methods (University of California Sierra Nevada Aquatic Research Laboratory [UC-SNARL, Lahontan Water Board], California Stream Bioassessment Protocol, and US Forest Service Region 5) differed at each stage from field sample collection to laboratory processing and data analysis. We used a performance-based methods system to compare precision, uniformity, discrimination, accuracy, and correlations among multimetric Index of Biotic Integrity (IBI) scores and multivariate River Invertebrate Prediction and Classification System (RIVPACS)-type observed/expected (O/E) ratios. Reference and test sites were identified using local and upstream-watershed disturbance criteria, and invertebrate community measures and models were then developed to discriminate between reference and test sites. The more-intensive UC-SNARL method showed slightly, but consistently, greater sensitivity for discriminating impairment than the other 2 methods. The UC-SNARL method produced greater differences between reference- and test-site means relative to lower reference-site standard deviations than the other 2 methods. However, assessment scores were highly correlated among methods and distinguished reference from test sites with similar accuracy among methods despite the slight differences in performance. Our results show that differing bioassessment methods can yield very similar, effective discrimination of impaired biological condition even though they have multiple differences in field and laboratory protocols (mesh size, replication, area sampled, taxonomic resolution, total counts). Moreover, this conclusion did not depend on the approach taken to data analysis because both multimetric IBIs and multivariate RIVPACS-type O/Es were in close agreement. Methodological uniformity is important when coordinating monitoring programs, but our results suggest that data from multiple sources could potentially be used interchangeably and for cross-validation of assessments of stream biological integrity.