Invertebrate Community Metrics Research Articles

Structure and functional composition of macroinvertebrate communities in coastal plain streams across a precipitation gradient

Abstract Climate change is expected to alter rainfall and temperature regimes across the world. The hydrology and riparian zone vegetation of lotic ecosystems are tightly linked to rainfall and a mechanistic understanding of the effects of rainfall on lotic ecosystems is needed to forecast the ecological impacts of climate change. However, it is difficult to isolate rainfall effects from other environmental variables that covary across climates. To address this, we leveraged a unique steep rainfall gradient with few covarying changes in elevation, temperature, and geology to evaluate the effects of rainfall on stream invertebrate communities. We surveyed nine streams in the Texas Gulf Coast Prairie distributed along a 550–1,350 mm/year rainfall gradient. Four sites were classified as drier semi‐arid streams (<750 mm annual rainfall) and five sites were classified as wetter sub‐humid streams (>750 mm annual rainfall). A suite of characteristics including benthic invertebrate community metrics, flow conditions, and water quality variables were assessed monthly for 14 months at each site to relate precipitation regime to stream structure and function. Precipitation regime was observed to be a master explanatory variable. As annual rainfall increased, the flow environment became more stable within seasons and predictable across seasons, influencing spatial structure and temporal variability of invertebrate community composition. Wetter streams were dominated by slower growing taxa without adaptions for desiccation resistance and strong dispersal. Wetter sites displayed seasonal variation in community composition and species richness, whereas temporal variation in communities in drier streams was controlled by stochastic variation in flow conditions. These observations show that differences in local annual rainfall correlated with major changes to community structure and functional composition. We hypothesise that this association is related to the connection of rainfall to hydrological stability, particularly the frequency of low flow disturbances, and the subsequent effects on riparian vegetation and temporally available niches to stream invertebrates. Our work adds to evidence that alterations in precipitation patterns associated with climate change have sweeping impacts on lotic fauna.

Long-Term Monitoring of an In Situ Activated Carbon Treatment to Reduce Polychlorinated Biphenyl Availability in an Active Harbor.

Activated carbon-based amendments have been demonstrated as a means of sequestering sediment-associated organic compounds such as polychlorinated biphenyls (PCBs). In a 2012 effort, an activated carbon amendment was placed at a 0.5-acre amendment area adjacent to and underneath Pier 7 at the Puget Sound Naval Shipyard and Intermediate Maintenance Facility, Bremerton, Washington, USA to reduce PCB availability. Multiple postplacement monitoring events over a 3-year period showed an 80%-90% reduction in PCBs, stability of activated carbon, and no significant negative impacts to the benthic community. To further evaluate the long-term performance, a follow-on to the approximately 7-year (82-month) postplacement monitoring event was conducted in 2019. The results of in situ porewater and bioaccumulation evaluations were consistent with previous observations, indicating overall PCB availability reductions of approximately 80%-90% from preamendment conditions. Multiple measurement approaches for quantifying activated carbon and amendment presence indicated that the amendment was present and stable in the amendment area and that the activated carbon content was similar to levels observed previously. As in the previous investigation, benthic invertebrate community metrics indicated that the amendment did not significantly impair benthic health. An application of carbon petrography to quantify activated carbon content in surface sediments was also explored. The results were found to correspond within a factor of 1.3 (on average) with those of data for the black carbon content via a black carbon chemical oxidation method, an approach that quantifies all forms of black carbon (including activated carbon). The results suggest that at sites with low soot-derived black carbon content in sediment (relative to the targeted activated carbon dose), the black carbon chemical oxidation method would be a reasonable method for measurement of activated carbon dosage in sediment at sites amended with activated carbon. Environ Toxicol Chem 2022;41:1568-1574. © 2022 SETAC.

Assessing the Ecological Status of European Rivers and Lakes Using Benthic Invertebrate Communities: A Practical Catalogue of Metrics and Methods

The Water Framework Directive requires that the ecological status of surface waters be monitored and managed if necessary. A central function in ecological status assessment has the Biological Quality Elements—organisms inhabiting surface waters—by indicating human impact on their habitat. For benthic invertebrates, a wide array of national methods are used, but to date no comprehensive summary of metrics and methods is available. In this study, we summarize the benthic invertebrate community metrics used in national systems to assess the ecological status of rivers, (very) large rivers, and lakes. Currently, benthic invertebrate assemblages are used in 26 national assessment systems for rivers, 13 assessment systems for very large rivers, and 21 assessment systems for lakes in the EU. In the majority of systems, the same metrics and modules are used. In the Red Queen’s race of ecosystem management this may be a disadvantage as these same metrics and module likely depict the same stressors but there is growing evidence that aquatic ecosystems are subject to highly differentiated, complex multiple stressor impacts. Method development should be fostered to identify and rank impacts in multi-stressor environments. DNA-based biomonitoring 2.0 offers to detect stressors with greater accuracy—if new tools are calibrated.

Multiple stressor effects on benthic macroinvertebrates in very large European rivers – A typology-based evaluation of faunal responses as a basis for future bioassessment

Two factors complicate the ecological status classification of very large rivers in Europe according to the EU Water Framework Directive: First, current assessment methods do not fully consider the specific ecology of very large rivers (such as lateral connectivity and the role of floodplains for ecological status). Second, most of Europe's very large rivers have been severely altered by human activities such as flood protection, damming and navigation. The aim of our study is to develop an assessment method for very large rivers by identifying suitable biological metrics as the basis for multi-metric bioassessment using benthic invertebrates. Based on the pan-European typology of very large rivers by Borgwardt et al. (2019), we established a river type-specific assessment approach using invertebrate samples from 25 European countries and 94 very large rivers. The frequency and intensity of eight pressures jointly acting on the sampling sites were described, and a selection of suitable invertebrate community metrics were correlated with the pressure intensities to establish pressure-response relationships. The very large river types differ in terms of relevant pressures and pressure combinations, with the invertebrate communities distinctly responding to these pressure patterns. Neozoa dominance correlated strongly with ‘navigation’, being a major pressure at very large rivers, which entails severe hydro-morphological alterations such as channelization, riparian vegetation alteration and impoundment. Under combined pressures, a critical community turnover became evident in terms of neozoa outnumbering EPT taxa and the ratio of hemilimnic invertebrates decreasing. We propose ten bioassessment metrics, including measures of biological diversity as well as newly generated indicators, for the development of a European type-specific assessment method for very large rivers.

Defining Maximum Ecological Potential for heavily modified lowland streams of Northern Italy

In relation to hydromorphological alteration the Water Framework Directive (WFD), a major piece of European legislation, has introduced the concept of Heavily Modified Water Bodies (HMWB). In water bodies falling in this category, hydromorphological modifications are permanent, significantly alter the character of the river and cannot be removed without compromising the use of the water body. In HMWBs a dedicated approach to the evaluation of their status is set, and their Ecological Potential must be assessed. Crucial to the process is the definition of Maximum Ecological Potential (MEP) as the reference conditions for HMWB. In the present paper we aim to define MEP conditions for Italian heavily modified lowland rivers, affected by strong bank protection (i.e. levees or bank reinforcement) in reason of flood protection and land drainage uses. The approach applied to identify MEP conditions follows the one considered for natural (not heavily modified) rivers in Italy and large part of Europe and bases on the identification of ‘reference sites’ representative for the river category and alteration. For the selection of MEP sites environmental features representing mitigation measures and/or expected natural features were considered. The ability of such features in discriminating MEP and disturbed sites was verified by multivariate analyses run on abiotic features (Principal Component Analysis) and biological communities (non-metric multidimensional scaling). We demonstrated differences both in terms of invertebrate community and biological metrics used to assess ecological status (and potential) between MEP and impaired river stretches. Finally, we recognized relevant habitat features able to clearly separate MEP reaches from nonMEP reaches with indication on the type and quantity of measures significant for benthic invertebrates and applicable in lowland Heavily Modified Water Bodies.

Influence of wildfire and harvesting on aquatic and terrestrial invertebrate drift patterns in boreal headwater streams

Forested headwater streams are strongly connected to their surrounding riparian areas via the transfer of energy subsidies that underpin instream food webs and, therefore, are highly sensitive to riparian disturbances that influence allochthonous inputs. We compared terrestrial and aquatic invertebrates found in drift across headwater streams in boreal forested catchments with wildfire, harvest with minimum 30-m riparian buffers, and reference catchment histories. Fire-disturbed streams contained significantly greater aquatic invertebrate abundance and biomass compared to reference and harvested streams, but no significant trends were seen for terrestrial invertebrate abundance or biomass. Furthermore, fire-disturbed streams supported distinct drifting invertebrate communities compared to reference and harvested sites, driven by high abundances of the mayfly Baetis and caddisfly Dolophilodes. Aquatic invertebrate drift communities were compositionally dissimilar between fire and harvested sites, but not reference sites and no trends were found for terrestrial invertebrate drift samples. Subtle but detectable differences in drifting invertebrate community metrics, structure, and biomass suggest that the effects of wildfire persist well beyond a decade post-fire in boreal headwater streams. Forest management that emulates natural fire disturbance, including streamside disturbance, may be important for promoting the observed patterns detected in our fire-disturbed catchments.

Effects of uranium mining and milling on benthic invertebrate communities in the Athabasca Basin of Northern Saskatchewan

Aquatic environments downstream of uranium operations (mining/milling) in Northern Saskatchewan are exposed to a variety of chemical and physical disturbances. There is extensive regulatory documentation of monitoring and effects assessments for modern uranium operations, though little is available in the scientific literature. The reference condition approach was used to predict expected benthic invertebrate community metrics for unexposed and exposed lakes. This approach was used to identify impacted communities that differed significantly from expected natural regional compositions. The number of taxa at the lowest practical level (taxon richness) downstream of approximately half of the uranium operations’ effluent release points was lower compared to the number of taxa observed in reference conditions. The taxon richness residuals were strongly correlated with about half of the measured concentrations of sediment contaminants and always negatively, such that richness was lower in lakes with higher concentrations of metals or radionuclide activities in the sediments. This was consistent for both reference and exposure lakes, implying a natural background influence of some metals and radionuclides on taxon richness. This exercise produced models that can be used by practitioners in the north of Saskatchewan in the design and delivery of monitoring programs not only for uranium mines, but for regional cumulative effects studies in support of sustainable resource planning and management.

How to assess the impact of fine sediments on the macroinvertebrate communities of alpine streams? A selection of the best metrics

Excessive fine sediment accumulation (i.e., siltation) in streams and rivers originates from several human activities and globally results in heavy alterations of aquatic habitats and biological communities. In this study the correlation between fine sediment and several benthic invertebrate community metrics was tested through a manipulative approach in alpine streams, where siltation mainly results as a physical alteration (i.e., the clogging of substrate interstices) without the influence of co-occurring confounding factors. We selected 12 candidate metrics, belonging to three different categories: compositional, structural and functional. We first carried out a manipulative experiment where artificial substrates were used to provide standardized conditions of siltation. All candidate metrics were calculated for each artificial substrate and the selection of the best combination of metrics was statistically performed with an information-theoretic approach. All candidate metrics were calculated both at family level and also at a mixed level (family and genus) in order to account for the systematic resolution. Then, data from a field study on alpine streams affected by mining activities were used as independent dataset for testing the performance of the selected metrics. We found that the total taxa richness, the EPT (Ephemeroptera, Plecoptera and Trichoptera) richness and the abundance of benthic invertebrates associated to rheophilous conditions and coarse mineral substrates were the most sensitive metrics. When these metrics were aggregated into a multimetric index in the validation dataset, we observed high and significant correlations between index values and the quantity of fine sediment for both taxonomic levels, especially for the mixed level. The findings of this study provide useful tools for biomonitoring the effects of fine sediment in low order, mountainous streams and contribute to improve our diagnostic ability on stressor-specific alterations.

Complex mixtures of dissolved pesticides show potential aquatic toxicity in a synoptic study of Midwestern U.S. streams

Aquatic organisms in streams are exposed to pesticide mixtures that vary in composition over time in response to changes in flow conditions, pesticide inputs to the stream, and pesticide fate and degradation within the stream. To characterize mixtures of dissolved-phase pesticides and degradates in Midwestern streams, a synoptic study was conducted at 100 streams during May–August 2013. In weekly water samples, 94 pesticides and 89 degradates were detected, with a median of 25 compounds detected per sample and 54 detected per site. In a screening-level assessment using aquatic-life benchmarks and the Pesticide Toxicity Index (PTI), potential effects on fish were unlikely in most streams. For invertebrates, potential chronic toxicity was predicted in 53% of streams, punctuated in 12% of streams by acutely toxic exposures. For aquatic plants, acute but likely reversible effects on biomass were predicted in 75% of streams, with potential longer-term effects on plant communities in 9% of streams. Relatively few pesticides in water—atrazine, acetochlor, metolachlor, imidacloprid, fipronil, organophosphate insecticides, and carbendazim—were predicted to be major contributors to potential toxicity. Agricultural streams had the highest potential for effects on plants, especially in May–June, corresponding to high spring-flush herbicide concentrations. Urban streams had higher detection frequencies and concentrations of insecticides and most fungicides than in agricultural streams, and higher potential for invertebrate toxicity, which peaked during July–August. Toxicity-screening predictions for invertebrates were supported by quantile regressions showing significant associations for the Benthic Invertebrate-PTI and imidacloprid concentrations with invertebrate community metrics for MSQA streams, and by mesocosm toxicity testing with imidacloprid showing effects on invertebrate communities at environmentally relevant concentrations. This study documents the most complex pesticide mixtures yet reported in discrete water samples in the U.S. and, using multiple lines of evidence, predicts that pesticides were potentially toxic to nontarget aquatic life in about half of the sampled streams.

In-stream water quality, invertebrate and fish community health across a gradient of dairy farming prevalence in a New Zealand river catchment

Dairying is an intensive form of agriculture influencing stream ecosystems worldwide via increased levels of nutrients, deposited fine sediment and other contaminants. However, it is not fully understood how dairy farming affects food supply for stream fish. We investigated relationships between dairy farming prevalence in the catchments of nine tributaries of a New Zealand river (0% to 79% of the catchment area) and fish and invertebrate communities. Streams were sampled four times at monthly intervals for brown trout density, fitness/growth-related trout response variables, native fish density, invertebrate community metrics as well as physical and chemical water quality variables. Densities of both brown trout and native fish declined as dairying increased, with no trout found in streams where dairy farms covered more than 50% of the catchment area. Increasing dairy farming prevalence was also associated with higher in-stream levels of dissolved nutrients and deposited fine sediment. These findings suggest that increasing the extent of dairy farming in New Zealand based on practices at the time of sampling results in less abundant and diverse fish communities.

Ecological risk assessment for residual coal fly ash at Watts Bar Reservoir, Tennessee: Limited alteration of riverine-reservoir benthic invertebrate community following dredging of ash-contaminated sediment.

Benthic invertebrate communities were assessed after the December 2008 release of approximately 4.1 million m(3) coal fly ash from a disposal dredge cell at the Tennessee Valley Authority (TVA) Kingston Fossil Plant on Watts Bar Reservoir in Roane County, Tennessee, USA. Released ash filled the adjacent embayments and the main channel of the Emory River, migrating into reaches of the Emory, Clinch, and Tennessee Rivers. Dredging was completed in summer 2010, and the benthic community sampling was conducted in December 2010. This study is part of a series that supported an Ecological Risk Assessment for the Kingston site. Benthic invertebrate communities were sampled at transects spread across approximately 20 miles of river that includes both riverine and reservoirlike conditions. Community composition was assessed on a grab sample and transect basis across multiple cross-channel transects to gain an understanding of the response of the benthic community to a fly ash release of this magnitude. This assessment used invertebrate community metrics, similarity analysis, geospatial statistics, and correlations with sediment chemistry and habitat. The community composition was reflective of a reservoir system, with dominant taxa being insect larva, bivalves, and aquatic worms. Most community metric results were similar for ash-impacted areas and upstream reference areas. Variation in the benthic community was correlated more with habitat than with sediment chemistry or residual ash. Other studies have reported that a benthic community can take several years to a decade to recover from ash or ash-related constituents. Although released ash undoubtedly had some initial impacts on the benthic community in this study, the severity of these effects appears to be limited to the initial smothering of the organisms followed by a rapid response and the initial start of recovery postdredging.

An extended Benthic Quality Index for assessment of lake profundal macroinvertebrates: addition of indicator taxa by multivariate ordination and weighted averaging

The chironomid Benthic Quality Index (BQI) is a widely used metric in assessments of lake status. The BQI is based on 7 indicator taxa, which like most profundal fauna, often occur sporadically in low densities. Hence, a major weakness of the index is that it cannot be calculated when indicator taxa are not captured. Thus, an extension of the BQI that incorporates more macroinvertebrate taxa is desirable. We used 2 statistical approaches (Detrended Correspondence Analysis and Weighted Averaging) to estimate new benthic quality indicator scores for profundal macroinvertebrate taxa and to construct modified BQIs called Profundal Invertebrate Community Metrics (PICMs). We calibrated the PICMs and evaluated their bioassessment performance with macroinvertebrate and environmental data from 735 lake basins in Finland. Both PICMs included 70 taxa and could be calculated for a substantially greater proportion (99.5%) of sites than the original BQI (83.5%). Compared to the BQI, the PICMs were more strongly correlated with whole-community variation and were more predictable from environmental factors independent of human activities in undisturbed reference lakes. PICMs were more specific in identifying undisturbed lakes and more sensitive in discriminating nonreference from reference lakes. The strength of relationships to total P concentration was equal among indices. These results suggest that the extension of BQI to incorporate more taxa will increase generality, accuracy, and representativeness of lake profundal macroinvertebrate assessment.

Aquatic Invertebrate Community Trends and Water Quality at Homestead National Monument of America, Nebraska, 1996–2012

To address concerns about water quality in Cub Creek, Homestead National Monument of America (HOME), Nebraska, the National Park Service began monitoring aquatic invertebrates annually beginning in 1996. Invertebrates were collected using Hester-Dendy multiplate samplers placed at two sampling sites on Cub Creek. Water quality parameters measured in the creek included temperature, dissolved oxygen, specific conductance, pH, turbidity, nitrate-nitrogen, total phosphorus, and fecal coliform bacteria (Escherichia coli). Most water quality measurements met state standards and were generally consistent and typical for streams of this size in the region, but phosphorus concentrations, turbidity, and fecal coliform bacteria levels greatly exceeded acceptable levels. Similarly, summary data for invertebrate community metrics, including low taxa richness, diversity and evenness, low Ephemeroptera, Plecoptera, Trichoptera (EPT) richness, and high Hilsenhoff Biotic Index (HBI) suggest that Cub Creek is not fully biologically supporting. However, invertebrate metrics generally did not exceed control chart limits based on historical data collected from 1996–2004, showing that since 2005 the metrics have not deviated significantly from their historical baseline. Additionally, Mann-Kendall trend test for each metric for the period 1996–2012 did not show significant trends (P ≥0.05) thus further indicating that stream integrity has not diminished beyond that when monitoring first began. Impacts to water quality in Cub Creek originate upstream of the monument boundaries, making mitigation difficult. Protecting and managing in-stream habitat and riparian zone integrity will aid in maintaining the integrity of Cub Creek flowing through the monument.

Invertebrate drift and colonization processes in a tropical Andean stream

We studied invertebrate drift (intensity, propensity, and diel changes) and the recolo - nization process of stones in a tropical high-altitude stream in Ecuador for a period of 7 to 25 d dur- ing the wet and dry seasons. Our aim was to identify whether seasonal differences in flow produce differences in drift parameters and in the recolonization process, and to examine the role of micro- habitat (fast-flow vs. slow-flow areas) in this process. Invertebrate community metrics in drift did not differ between seasons at base flow (<100 l s �1 ), but they were highly correlated with high flow events. As a result, drift propensity values for several taxa were higher during the wet season, when higher flows occurred, indicating that some taxa suffer catastrophic drift (e.g. Podonominae, Simuliidae). In the short-term experiment, taxa richness, density, and diversity of the colonizers increased with time (up to Day 7). On a longer scale (Days 7 to 25; mid-term experiment), time did not affect community metrics. Microhabitat had strong effects on the composition of colonized stones, and was related to the abundance of taxa in the drift. While some taxa that are scarce in drift were only found in slow-flow areas (e.g. Nectopsyche), suggesting that these species actively search for refuges in the stream, copious species in the drift (e.g. Baetodes) were very abundant on the recolonizing stones, especially during the wet season. The present study suggests that flow, the variability of flow (within and between seasons), and its consequences on the drift of several species play a pivotal role in invertebrate colonization and in the structuring of invertebrate communities in different microhabitats of high-altitude tropical streams.

Linking disturbance and stream invertebrate communities: how best to measure bed stability

Substrate stability is a key determinant of stream invertebrate community composition, but its measurement can be problematic. Stream ecologists often use different approaches and techniques to quantify bed stability, and this variability makes comparison among studies difficult. We examined the link between 6 reach-scale measures of substrate stability and invertebrate community metrics in 12 New Zealand mountain streams. The strength of the link varied with the method used to define substrate stability. We used morphological budgeting to measure spatial patterns and volumes of scour and fill. We found that as erosion of sediments increased, invertebrate diversity declined exponentially. In particular, increases in the volume of scour reduced taxonomic richness, whereas deposition of coarse sediments was less relevant for invertebrate communities. Overall, the distance travelled by in-situ-marked tracer stones was most strongly linked with all invertebrate community metrics, whereas the bottom component of the Pfankuch Index related very well to diversity. Both metrics showed near-linear declines in diversity with decreasing stability. In contrast, the link between invertebrate communities and the proportion of bed area affected by entrainment was weak. Therefore, we propose tracer-based indices and the Pfankuch bottom component as the most suitable measures for research involving invertebrate–substrate-stability relationships. Measures derived from in-situ-marked tracer stones reflected only entrainment and transport of particles. In contrast, the bottom component of the Pfankuch Index encompassed the widest range of bed-stability characteristics but is prone to observer bias. An objective method that combines the efficiency of the Pfankuch Index with the characteristics measured using tracer stones could serve as a powerful explanatory tool in stream ecology.

Determination of biologically significant hydrologic condition metrics in urbanizing watersheds: an empirical analysis over a range of environmental settings

We investigated the relations among 83 hydrologic condition metrics (HCMs) and changes in algal, invertebrate, and fish communities in five metropolitan areas across the continental United States. We used a statistical approach that employed Spearman correlation and regression tree analysis to identify five HCMs that are strongly associated with observed biological variation along a gradient of urbanization. The HCMs related to average flow magnitude, high-flow magnitude, high-flow event frequency, high-flow duration, and rate of change of stream cross-sectional area were most consistently associated with changes in aquatic communities. Although our investigation used an urban gradient design with short hydrologic periods of record (≤1 year) of hourly cross-sectional area time series, these five HCMs were consistent with previous investigations using long-term daily-flow records. The ecological sampling day often was included in the hydrologic period. Regression tree models explained up to 73, 92, and 79% of variance for specific algal, invertebrate, and fish community metrics, respectively. National models generally were not as statistically significant as models for individual metropolitan areas. High-flow event frequency, a hydrologic metric found to be transferable across stream type and useful for classifying habitat by previous research, was found to be the most ecologically relevant HCM; transformation by precipitation increased national-scale applicability. We also investigated the relation between measures of stream flashiness and land-cover indicators of urbanization and found that land-cover characteristic and pattern variables, such as road density, percent wetland, and proximity of developed land, were strongly related to HCMs at both a metropolitan and national scale and, therefore, may be effective land-use management options in addition to wholesale impervious-area reduction.

Use of littoral benthic invertebrates to assess factors affecting biological recovery of acid- and metal-damaged lakes

AbstractBiological recovery of aquatic ecosystems from acidification damage is a slow process. In lakes near the massive Cu and Ni smelters in Sudbury, Canada, the delays might be caused by residual metals, habitat damage, altered predator–prey interactions, or other persistent ecological stressors. Assessments of benthic invertebrate communities in 24 Sudbury lakes were conducted to evaluate the relative importance of these delaying factors. At the time of sampling, all lakes had chemically recovered to a pH >6.0, but they varied widely in the duration of time above this threshold and in current metal concentrations, watershed contributions of organic matter, littoral habitat composition, and fish community composition. A model developed with redundancy analyses (RDA) of 4 groups of environmental variables (i.e., water chemistry, fish communities, physical lake descriptors, and littoral habitat) accounted for 74.9% of the variance in benthic invertebrate community metrics across these environmental gradi...

Catchment‐scale effects of forestry practices on benthic invertebrate communities in Pacific coastal streams

Summary 1. Catchment‐scale effects of forestry practices alter stream physical structures and influence composition and abundance of benthic communities. Looking beyond the reach‐scale effects to disturbance impacts that come from upstream catchments is rare. Understanding of effects of large‐scale catchment disturbances on downstream habitats is crucial to better manage the impacts or mitigate the effects of forest management. 2. By comparing catchments with different forestry histories, we examined the impacts of past forestry practices on stream habitats and benthic invertebrate diversity in six reference streams in mature forests and five previously logged streams in young‐growth forests in the Chilliwack River basin, Canada. Principal components analysis separated the reference streams and the previously logged streams by their physical characteristics. Streams in mature forests had coarser substrates than in young‐growth forests. 3. Using partial least squares projection to latent structures (PLS) modelling, we assessed the relationship between multiple environmental variables and benthic communities. Predictive PLS models were developed based on environmental variables and community response variables at reference streams. The observed taxon richness and relative abundance of total benthos, scrapers and predators at previously logged sites were significantly lower than the model predicted. The biomasses of total benthos and shredders at previously logged sites were significantly lower than those at reference sites. 4. Synthesis and applications. This study demonstrates that a legacy of measurable logging impacts on habitats and invertebrate community metrics can be detected up to 40 years after logging on these streams and at a catchment‐scale. This predictive model approach combined with intensive field observations has potential for assessing the catchment‐scale effects of forestry on stream ecosystems. This method also can be used to estimate the time to recovery from harvesting and to assist the evaluation of improving management decisions to reduce the negative impacts of forest harvesting on stream ecosystems.

Does the lentic-lotic character of rivers affect invertebrate metrics used in the assessment of ecological quality?

The importance of local hydraulic conditions on the structuring of freshwater biotic communities is widely recognized by the scientific community. In spite of this, most current methods based upon invertebrates do not take this factor into account in their assessment of ecological quality. The aim of this paper is to investigate the influence of local hydraulic conditions on invertebrate community metrics and to estimate their potential weight in the evaluation of river water quality. The dataset used consisted of 130 stream sites located in four broad European geographical contexts: Alps, Central mountains, Mediterranean mountains and Lowland streams. Using River Habitat Survey data, the river hydromorphology was evaluated by means of the Lentic-lotic River Descriptor and the Habitat Modification Score. To quantify the level of water pollution, a synoptic Organic Pollution Descriptor was calculated. For their established, wide applicability, STAR Intercalibration Common Metrics and index were selected as biological quality indices. Significant relationships between selected environmental variables and biological metrics devoted to the evaluation of ecological quality were obtained by means of Partial Least Squares regression analysis. The lentic-lotic character was the most significant factor affecting invertebrate communities in the Mediterranean mountains, even if it is a relevant factor for most quality metrics also in the Alpine and Central mountain rivers. Therefore, this character should be taken into account when assessing ecological quality of rivers because it can greatly affect the assignment of ecological status.

Use of Field Data to Support European Water Framework Directive Quality Standards for Dissolved Metals

Quality standards (QS) for dissolved metals in freshwaters have been proposed underthe European Water Framework Directive (WFD) and are based mainly upon laboratory ecotoxicity data. Uncertainties remain about laboratory-to-field extrapolation to establish QS that are neither over- nor underprotective. Freshwater benthic macroinvertebrates are a group of organisms of known sensitivity to heavy metals. We analyzed a dataset from England and Wales of dissolved metal concentrations (cadmium, chromium, copper, iron, nickel, lead, and zinc) and associated benthic invertebrate community metrics, using piecewise regression, quantile regression, and information on metal concentrations consistent with good quality status. Analysis of these field data suggests that dissolved metal QS proposed under the WFD are similar to metal concentrations in rivers associated with unimpaired benthic invertebrate assemblages in England and Wales. The only exceptions to this are QS for iron and zinc, where use of relatively large assessment factors leads to standards that are substantially below concentrations associated with impaired invertebrate assemblages in the field.