Assessment of Stream Restoration: Sources of Variation in Macroinvertebrate Recovery throughout an 11‐Year Study of Coal Mine Drainage Treatment

Stream restoration researchers have a complex array of alternative assessment methodologies using macroinvertebrates. We examined sources of variation among three field sampling methods and five metrics in three networked streams impacted by a circumneutral coal mine discharge treated midway through an 11‐year study. Constructed wetlands captured the primary stressor, 700 kg iron/day. Before pollution abatement, copious iron hydroxide smothered downstream sites for decades. Two second‐order streams and one fourth‐order receiving stream, each with matching locations upstream and downstream, were monitored midsummer from 1994 to 2004. We compared taxa density (TD) (number/sample), abundance, expected taxa richness (ETR), U.S. regional pollution tolerance values (RTV), and community similarity (CS) indices from 3 to 11 replicate samples/site using grab samples (i.e. D‐nets, rock washes) and incubated leaf packs. Variation due to sampling method, metric, location, and year significantly influenced outcomes when analyzed using regression and analysis of variance. TD, RTV, and CS indicated biological recovery lagged 6 years behind chemical improvement; ETR and abundance showed more severe, persistent impairment in the two, highly impacted second‐order streams compared to the fourth‐order stream. Incubated leaf packs offered a preview of stream recovery in downstream sites, providing clean food (leaves) and substrate (mesh) and attracted more taxa and abundance than grab samples. In light of the worldwide distribution of coal mining often accompanied by metal hydroxide deposits into streams, we suggest restoration project managers use a variety of sampling methods, metrics, and models to evaluate remediation of physical as well as chemical impairment from mining.     

Hydromorphological degradation impact on benthic invertebrates in large rivers in Slovenia

Large rivers are amongst the most degraded ecosystems. We studied a relationship between hydromorphological degradation and benthic invertebrates in large rivers in Slovenia. Five indices of the Slovenian hydromorphological assessment methodology were used to develop a HM stressor gradient. Natural type-specific habitat diversity was considered in the hydromorphological stressor gradient building and thus two hydromorphological types of large rivers were defined. CCA ordination with five HM indices and 315 benthic invertebrate taxa revealed variations in taxa response along the HM stressor gradient. First CCA axis species values were used to develop a taxon-specific river fauna value (Rf_i), whereas tolerance values (biplot scaling) were used to determine a hydromorphological indicative weight (HW_i). Rf_i, HW_i, and log₅ abundance classes were combined using weighted average approach to construct a River fauna index for large rivers (RFI_VR). Several additional benthic invertebrate-based metrics were also tested against the HQM. A Slovenian multimetric index for assessing the hydromorphological impact on benthic invertebrates in large rivers (SMEIH_VR) was constructed from the RFI_VR and a functional metric %akal + lithal + psammal taxa (scored taxa = 100%). The strong relationship between hydromorphological stressor gradient and SMEIH_VR index provides us with an effective assessment system and river management tool.     

A stressor specific multimetric approach for monitoring running waters in Austria using benthic macro-invertebrates

We investigated four stream types in four different bioregions, classified by catchment area and altitude, and stressed by different degrees of organic pollution and habitat alteration. We examined a macro-invertebrate based multimetric approach for Austrian rivers as a potential assessment method within the European Water Framework Directive. Benthic macro-invertebrate data (100 samples including reference sites) were used to develop a multimetric index for each stream type and targeted stressors. Sites were pre-classified based on physical, chemical, and land use criteria into five ecological quality classes. More than 200 biological metrics were tested for their sensitivity to the targeted stressors, their spatial and temporal variability and their ability to discriminate between different types and degrees of stress. Metrics for index development were selected to reflect different levels of information including ecosystem, community, and individual levels (Karr, 1991; Barbour et al., 1995; Gerritsen, 1995). Combinations of metrics were selected to distinguish best between non or slightly impaired and stressed sites (evaluated by calculating discrimination efficiency values and power analysis). The resulting four indices comprised seven to nine metrics from five to seven metric categories, and distinguished reference/slightly disturbed sites from stressed sites with close to 100% efficiency. The indices can form the basis for stressor-specific assessment of stream condition.     

Assigning macroinvertebrate tolerance classifications using generalised additive models

1. Macroinvertebrates are frequently classified in terms of their tolerance to human disturbance and pollution. These tolerance values have been used effectively to assess the biological condition of running waters. 2. Generalised additive models were used to associate the presence and absence of different macroinvertebrate genera with different environmental gradients. The model results were then used to classify each genera as sensitive, intermediately tolerant or tolerant to different stressor gradients as quantified by total phosphorus concentration, sulphate ion concentration, qualitative habitat score and stream pH. The analytical approach provided a means of estimating stressor‐specific tolerance classifications while controlling for covarying, natural environmental gradients. 3. Computed tolerance classification generally conformed with expectations and provided some capacity for distinguishing between different stressors in test data.     

Impact of human activities on stonefly (Insecta,Plecoptera) ecological metrics in the Hron River (Slovakia)

A total of 57 stonefly species have been recorded in the Hron River. The natural gradient (slope and stream width) and pollution gradient of the river were defined using CCA based on physical, chemical and stonefly data. Stonefly metrics (abundance, richness/diversity, sensitivy/tolerance and functional metrics) were used to estimate the quality of the Hron River and the degree of proximity to its natural state. Similar results were obtained using two different methods. The first method was based on the homogeneity of variance and the interquartile range of different groups of stretches of the Hron River and the second was based on deviations from the expected values of biological metrics in a given stretch of the river. These values continuously decreased with increasing distance from the spring area, with the exception of the saprobic index, which increased in a downstream direction, and the stonefly average score, which did not change significantly along the whole river flow. The Stonefly Average Score (SAS) metric is universal for a variety of habitats such as the Hron River upstream and downstream, and is a reliable indicator of water quality and the natural course of a stream.     

Measuring human disturbance using terrestrial invertebrates in the shrub–steppe of eastern Washington (USA)

Hanford Nuclear Reservation in eastern Washington is an ideal place to study biological responses to diverse human activities because minimally disturbed areas of native shrub–steppe exist in close proximity to areas that have been substantially altered. This range of conditions provides an opportunity to test which attributes of terrestrial invertebrate assemblages change systematically along a gradient of human influence and to select from these a set of biological metrics that can be used for site assessment. We sampled invertebrates at 25 sites at or near the Hanford Reservation: some sites showed past or present influence from agriculture, waste disposal, urbanization, or construction; others had a history of minimal human disturbance.We evaluated 57 attributes of terrestrial invertebrate assemblages to determine if they varied systematically with the intensity of human disturbance. Attributes were measured as taxa richness or percentage relative abundance of key taxonomic, trophic, or ecological groups. Ten attributes were consistently associated with disturbance in 3 years of independent sampling, and another 12 attributes were significant in 2 out of 3 years. Those selected as metrics were total number of invertebrate families (1) number of Diptera families (2) taxa richness of Acarina (3) predators (4) detritivores (5) ground-dwellers (6) and percentage relative abundance of detritivores (7); all declined with increasing disturbance. The percentage relative abundance of Collembola (8) and taxa richness (9) and relative abundance (10) of polyphagous Carabidae increased with disturbance. Two metrics (7 and 10) were excluded from further consideration because they were redundant with other metrics (6 and 9).We transformed the remaining eight metrics to a standard scale and added them to yield a multimetric index—a single value summarizing the biological condition of each site. Undisturbed sites had the highest index values; sites with physical disturbance related to construction or waste disposal ranked next; and agricultural sites had the lowest values, indicating the most severe changes in their resident biota. Index values were lower for more frequently disturbed sites, although the time since last disturbance produced no differences in index values. Repeat sampling at five sites indicated that index values varied little across years and that year-to-year differences were smaller at undisturbed than disturbed sites.This first effort to develop a terrestrial monitoring approach modeled after the aquatic index of biological integrity (IBI) shows promise, but validation of the metrics at other places will be needed before a terrestrial index of biological integrity (T-IBI) can reliably guide management, restoration, or policy decisions.     

Quantitative hydrological preferences of benthic stream invertebrates in Germany

Current knowledge regarding the flow preferences of benthic stream invertebrates is mostly based on qualitative data or expert knowledge and literature analysis. These established flow preferences are difficult to use in predictions of the effects of global change on aquatic biota. To complement the existing categories, we performed a large-scale analysis on the distribution of stream invertebrates at stream monitoring sites in order to determine their responses to various hydrological conditions.We used 325 invertebrate surveys from environmental agencies at 238 sites paired to 217 gauges across Germany covering a broad range of hydrological conditions. Based on these data, we modelled the respective probabilities of occurrences for 120 benthic invertebrate taxa within this hydrological range using hierarchical logistic regression models.Our analyses revealed that more than one-third of the taxa (18–40%) can be considered as ubiquitous and having a broad hydrological tolerance. Furthermore, 22–41% of the taxa responded to specific ranges of flow conditions with detectable optima. “Duration high flow event” represented the flow parameter that correlated best with the abundance of individual taxa, followed by “rate of change average event”, with 41 and 38% of the taxa showing a peak in their probability of occurrence at specific ranges of these metrics, respectively. The habitat suitability for these taxa may be potentially affected by global change-induced hydrological changes.Quantified hydrological traits of individual taxa might therefore support stream management and enable the prediction of taxa responses to flow alteration. The hydrological traits of stream benthic invertebrates may be used in forecasting studies in central Europe, and the methods used in this study are suitable for application in other regions with different flow regimes.     

Effects of stream size on taxa richness and other commonly used benthic bioassessment metrics

Benthic macroinvertebrate samples were collected from natural substrates in disturbed and undisturbed South Carolina upper coastal plain streams to determine if taxa richness and other bioassessment metrics were significantly related to stream size as predicted by the River Continuum Concept (RCC). Linear, quadratic, and lognormal regression models indicated that stream width was positively related to total number of taxa; number of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa; and total number of organisms. Linear regression showed that the expected number of taxa at undisturbed sites ranged from 35 in 2.0 m wide streams to 64 in 16.0 m streams. Comparable values were 8–20 for EPT and 109–261 for number of organisms. Stream width was inversely related to biotic index values indicating a decrease in average organism tolerance with increasing stream size. ANCOVA showed that the effects of stream size were similar for disturbed and undisturbed sites. Rank correlations and multidimensional scaling (MDS) showed that Lepidoptera and Trichoptera were more abundant in larger streams and Annelida in smaller streams. Stream size related changes in benthic macroinvertebrate community composition are often ignored in bioassessment protocols; however, failure to adjust metrics for stream size can lead to erroneous conclusions. Adjustments are possible by analyzing regression residuals stripped of stream size related variance, dividing the area beneath the maximum taxa richness line into equal size units for metric scoring, or scaling metrics based on predicted reference values. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Stressor prioritisation in riverine ecosystems: Which environmental factors shape benthic invertebrate assemblage metrics?

Aquatic ecosystems are amongst the most heavily altered ecosystems and exhibit a disproportional loss of biodiversity. Numerous stressors, such as nutrient enrichment, contaminant pollution, sedimentation and alterations in stream hydrology and habitat structure, account for these losses. Understanding these forces is of utmost importance to prevent riverine ecosystems from further deterioration and to provide helpful insights for restoration practices. In the present study, we analyse the response of biological indicators to a large number of environmental factors. For this, benthic invertebrate assemblages from 83 sites in Germany were described based on 25 metrics from four different metric types. The condition of the sites was described using 27 environmental factors: 13 for water quality, 4 for land use in the catchment and 10 for local scale habitat structure. The relative importance of single environmental predictors or predictor combinations for benthic invertebrate assemblages was analysed with single and multiple linear regression models. The results for the latter models were statistically supported via a bootstrap approach. The models revealed the importance of water quality and catchment-scale land use in explaining benthic invertebrate assemblages; in particular, chloride, oxygen, total organic carbon and the amounts of artificial surfaces and arable land were the most important predictors. Models including solely structural variables such as plan form, bank structures and substrate diversity had lower goodness of fit values than those for other variables. Regarding the four different assemblage metric types, functional metrics had on average lower goodness of fit values than composition/abundance, richness/diversity and sensitivity/tolerance metrics. Among the richness/diversity metrics, however, the model results for the Shannon–Wiener and Simpson diversity indices and evenness were poor. Our results show that catchment-related factors and water quality were of overriding importance in shaping biodiversity patterns and causing species loss. In contrast, structural degradation at a local scale was not the most significant stressor. This finding might explain why structural restoration at a reach scale often yields a low benefit–cost ratio and may be considered to represent inappropriate investment prioritisation.     

Multiple-stressor effects on stream invertebrates: DNA barcoding reveals contrasting responses of cryptic mayfly species

Most freshwater ecosystems are subject to multiple anthropogenic stressors, which commonly reduce biodiversity across all levels. Existing freshwater bioassessment programmes aim at identifying responses of aquatic biota to stressors. For practical reasons, higher-level taxonomic groups (e.g. genus or family) are often used in these programmes. This approach, however, may bias assessment results as different species can differ substantially in their biological traits, thus emphasising the need for species-level data. DNA barcoding can reliably generate species-level data for animals by sequencing a fragment of the mitochondrial cytochrome c oxidase subunit I gene (COI). This allows investigating species-specific responses to environmental stressors. In this study, we sampled 43 stream sites in southern New Zealand spanning wide gradients of agricultural stressors (fine sediment and nutrient levels). We first used conventional morphological assessment to determine stream invertebrate responses to the stressors, focusing on two important indicator taxa, the mayfly Deleatidium and the snail Potamopyrgus. We then tested for the presence of cryptic species in Deleatidium and Potamopyrgus using DNA barcoding of the COI gene for 520 and 305 specimens, respectively. While all Potamopyrgus specimens belonged to a single species, Deleatidium consisted of 12 distinct molecularly identified clades that likely represent distinct species. Finally, we compared stressor responses assessed at genus and species level. While overall Deleatidium abundance was unrelated to stressor levels, some of the individual clades differed clearly in the magnitude and direction of their responses to nutrient and sediment stress. While the most abundant cryptic Deleatidium clade (clade 1) showed no relationship to sediment or nutrient levels, clades 2 and 3 responded negatively to nutrient or sediment increases, respectively. These contrasting patterns indicate that individual freshwater invertebrate species, often merged to a higher taxonomic level for biomonitoring purposes, can differ substantially in their tolerance to stressors and respond in more complex ways than observed at genus level. Overall, our results highlight the considerable potential and importance of including DNA barcoding into freshwater ecosystem assessment and biomonitoring programmes.     

Prediction of taxon occurrence: a test on taxon‐specific change point values of stream benthic invertebrates

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A comparison of algal,macroinvertebrate, and fish assemblage indices for assessing low-level nutrient enrichment in wadeable Ozark streams

Biotic indices for algae, macroinvertebrates, and fish assemblages can be effective for monitoring stream enrichment, but little is known regarding the value of the three assemblages for detecting perturbance as a consequence of low-level nutrient enrichment. In the summer of 2006, we collected nutrient and biotic samples from 30 wadeable Ozark streams that spanned a nutrient-concentration gradient from reference to moderately enriched conditions. Seventy-three algal metrics, 62 macroinvertebrate metrics, and 60 fish metrics were evaluated for each of the three biotic indices. After a group of candidate metrics had been identified with multivariate analysis, correlation procedures and scatter plots were used to identify the four metrics having strongest relations to a nutrient index calculated from log transformed and normalized total nitrogen and total phosphorus concentrations. The four metrics selected for each of the three biotic indices were: algae—the relative abundance of most tolerant diatoms, the combined relative abundance of three species of Cymbella, mesosaprobic algae percent taxa richness, and the relative abundance of diatoms that are obligate nitrogen heterotrophs; macroinvertebrate—the relative abundance of intolerant organisms, Baetidae relative abundance, moderately tolerant taxa richness, and insect biomass; fish—herbivore and detritivore taxa richness, pool species relative abundance, fish catch per unit effort, and black bass (Micropterus spp.) relative abundance.All three biotic indices were negatively correlated to nutrient concentrations but the algal index had a higher correlation (rho = ?0.89) than did the macroinvertebrate and fish indices (rho = ?0.63 and ?0.58, respectively). Biotic index scores were lowest and nutrient concentrations were highest for streams with basins having the highest poultry and cattle production. Because of the availability of litter for fertilizer and associated increases in grass and hay production, cattle feeding capacity increases with poultry production. Studies are needed that address the synergistic effect of poultry and cattle production on Ozark streams in high production areas before ecological risks can be adequately addressed.     

Patterns of benthic algae and cyanobacteria along twin‐stressor gradients of nutrients and fine sediment: a stream mesocosm experiment

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Developing a multimetric index of ecological integrity based on macroinvertebrates of mountain ponds in central Italy

The lack of biological systems for the assessment of ecological quality specific to mountain ponds prevents the effective management of these natural resources. In this article we develop an index based on macroinvertebrates sensitive to the gradient of nutrient enrichment. With this aim, we sampled 31 ponds along a gradient of trophy and with similar geomorphological characteristics and watershed use in protected areas of the central Apennines. A bioassessment protocol was adopted to collect and process benthic samples and key-associated physical, chemical, and biological variables during the summer growth season of 1998. We collected 61 genera of macroinvertebrates belonging to 31 families. We calculated 31 macroinvertebrate metrics based on selected and total taxa richness, richness of some key groups, abundance, functional groups and tolerance to organic pollution. The gradient of trophy was quantified with summer concentrations of chlorophyll a. We followed a stepwise procedure to evaluate the effectiveness of a given metric for use in the multimetric index. Those were the pollution tolerance metric ASPT, three metrics based on taxonomic richness (the richness of macroinvertebrate genera, the richness of chironomid taxa, and the percentage of total richness composed by Ephemeroptera, Odonata, and Trichoptera), two metrics based on FFG attributes (richness of collector gatherer taxa and richness of scraper taxa) and the habit-based metric richness of burrowers. The 95th percentile of each metric distribution among all ponds was trisected for metric scoring. The final Pond Macroinvertebrate Integrity Index ranged from 7 to 35 and had a good correlation (R ² = 0.71) with the original gradient of environmental degradation. Guest editors: R. Céréghino, J. Biggs, B. Oertli & S. Declerck The ecology of European ponds: defining the characteristics of a neglected freshwater habitat     

Algal assemblages for large river monitoring: Comparison among biovolume,absolute and relative abundance metrics

Periphyton and phytoplankton samples were collected and analyzed from 393 locations in three mid-continent (US) great rivers: the Upper Mississippi, Missouri and Ohio. From the 410 taxa identified, 303 taxa were common enough for multivariate analyses. Algae assemblages were quantified by multiple metrics including biovolume (based on algal shape formulae and cell measurements), relative biovolume, cell density, relative cell density, entity density (based on numbers of colonies, filaments or free-living cells), and relative entity density. Relationships between algal metrics and both water quality (e.g., nutrients, ionic properties, physicochemical parameters) and landscape-scale stressor data (e.g., proportions watershed with agriculture and urban development, impoundment, pollution point-sources) were examined using multivariate analyses. Overall, algal metrics were more closely related to water quality than to landscape stressors. Phytoplankton cell density was the best indicator of water quality with 45% of the variance in the taxonomic data explained. We suspect that relationships between periphyton and water quality were weaker because water grab samples did not reflect the prevailing conditions to which the periphyton had been exposed. Phytoplankton also had a slightly stronger relationship to landscape-scale stressor data than did periphyton. Biovolume metrics were the best periphytic indicators of water quality and stressors. Absolute algal metrics, especially cell density, consistently had stronger relationships to water quality and stressors than relative (percentage-based) metrics.     

Multimetric assessment of data provided by water managers from Germany: assessment of several different types of stressors with macrozoobenthos communities

Our study attempted a new approach to biological assessment in Germany that would comply with the requirements of the European Union Water Framework Directive. We developed a multimetric index for use throughout Germany, based on the macrozoobenthos and devised along the guidelines formulated by Karr & Chu (1999). The index contains twelve measures, chosen for their discriminatory power in assessing general impairment as well as specific stressors (e.g., impoundments, acidification, organic or chemical pollution), the inclusion of all meaningful ecological metric categories, interrelationship as low as possible and the feasibility of using them in all geographic stream classes of Germany. Due to the availability of data over time the method was developed in three steps. In step 1 we studied the stressor specific response of biological attributes to additional stress by comparing each of 162 sites impaired by a known factor with a nearby site, which was morphologically comparable, but impaired to a lesser extent. The resulting list of 17 candidate metrics for a multimetric index was validated in step 2 using a set of model data from our own investigations. This step included data from not or minimally disturbed reference sites and the design of a five-class-scale of human impact to permit the use of dose-response curves, but no differentiation of stream types. The multimetric index IBI 12 was developed using dose-response curves, correlation coefficients and graphical analysis. The index was improved in the third step, calculations for this based on a dataset containing about 4000 macrozoobentos samples from over 900 streams and rivers in Germany, collected by water management authorities and researchers. The final version of the method uses type specific reference conditions, but the same set of 12 metrics for all stream types. This new IBI 12 is suitable to fulfil the requirements of the EU Water Framework Directive. It correlates with a Spearman's R of 0.76 with the general state of impairment for every stream type, and a Spearman's R between 0.6 and 0.87 with the most important specific stressors like sewage or morphological degradation. It proved to correlate higher with those stressors than any single index as yet used in Germany. The stressor specific analysis also substantiated that no single metric was really stressor specific with the exception of an acidity index. Even the well established Saprobic indices responded quite well to other stressors besides organic pollution. The results suggest that a separate assessment of specific stressors might be only possible by analysing the reaction pattern of an array of metrics. Further improvement of the index could be achieved by advances in stream typology and the reference conditions, as well as by a higher degree of standardisation to decrease the scatter caused by variations in sampling season, methodology and determination level.     

Impacts of multiple anthropogenic stressors on stream macroinvertebrate community composition and functional diversity

Ensuring the provision of essential ecosystem services in systems affected by multiple stressors is a key challenge for theoretical and applied ecology. Trait‐based approaches have increasingly been used in multiple‐stressor research in freshwaters because they potentially provide a powerful method to explore the mechanisms underlying changes in populations and communities. Individual benthic macroinvertebrate traits associated with mobility, life history, morphology, and feeding habits are often used to determine how environmental drivers structure stream communities. However, to date multiple‐stressor research on stream invertebrates has focused more on taxonomic than on functional metrics. We conducted a fully crossed, 4‐factor experiment in 64 stream mesocosms fed by a pristine montane stream (21 days of colonization, 21 days of manipulations) and investigated the effects of nutrient enrichment, flow velocity reduction and sedimentation on invertebrate community, taxon, functional diversity and trait variables after 2 and 3 weeks of stressor exposure. 89% of the community structure metrics, 59% of the common taxa, 50% of functional diversity metrics, and 79% of functional traits responded to at least one stressor each. Deposited fine sediment and flow velocity reduction had the strongest impacts, affecting invertebrate abundances and diversity, and their effects translated into a reduction of functional redundancy. Stressor effects often varied between sampling occasions, further complicating the prediction of multiple‐stressor effects on communities. Overall, our study suggests that future research combining community, trait, and functional diversity assessments can improve our understanding of multiple‐stressor effects and their interactions in running waters.     

COMPARISON OF SIMPLE AND MULTIMETRIC DIATOM‐BASED INDICES FOR GREAT LAKES COASTLINE DISTURBANCE1

Because diatom communities are subject to the prevailing water quality in the Great Lakes coastal environment, diatom‐based indices can be used to support coastal‐monitoring programs and paleoecological studies. Diatom samples were collected from Great Lakes coastal wetlands, embayments, and high‐energy sites (155 sites), and assemblages were characterized to the species level. We defined 42 metrics on the basis of autecological and functional properties of species assemblages, including species diversity, motile species, planktonic species, proportion dominant taxon, taxonomic metrics (e.g., proportion Stephanodiscoid taxa), and diatom‐inferred (DI) water quality (e.g., DI chloride [Cl]). Redundant metrics were eliminated, and a diatom‐based multimetric index (MMDI) to infer coastline disturbance was developed. Anthropogenic stresses in adjacent coastal watersheds were characterized using geographic information system (GIS) data related to agricultural and urban land cover and atmospheric deposition. Fourteen independent diatom metrics had significant regressions with watershed stressor data; these metrics were selected for inclusion in the MMDI. The final MMDI was developed as the weighted sum of the selected metric scores with weights based on a metric’s ability to reflect anthropogenic stressors in the adjacent watersheds. Despite careful development of the multimetric approach, verification using a test set of sites indicated that the MMDI was not able to predict watershed stressors better than some of the component metrics. From this investigation, it was determined that simpler, more traditional diatom‐based metrics (e.g., DI Cl, proportion Cl‐tolerant species, and DI total phosphorus [TP]) provide superior prediction of overall stressor influence at coastal locales.     

基于B-IBI指数的温榆河生态健康评价

基于温榆河底栖动物和水质采样数据,采用底栖动物完整性指数(B-IBI)方法,进行温榆河生态健康评价,并探求河流水质与B-IBI指数的相关性。通过分布范围、判别能力以及相关性分析等,确定研究区B-IBI指标体系,包括总分类单元数、总生物量、优势分类单元个体相对丰度、敏感类群分类单元数、生物指数和粘附者个体丰度6个指标。根据参照点25%分位数确定温榆河底栖动物完整性评价标准,即B-IBI>1.821为健康,1.366—1.821为亚健康,0.910—1.366为一般,0.455—0.910为较差,0—0.455为极差。结果表明,温榆河27.3%河段处于健康状态,9.1%河段处于亚健康状态,13.6%河段处于一般状态,50%河段处于较差和极差状态。河流水质与B-IBI指数的相关系数为-0.549,表明生物指标作为水体评价的补充指标十分必要。