Surber and kick sampling: a comparison for the assessment of macroinvertebrate community structure in streams of south-western Australia

Macroinvertebrate community structure was compared in benthic samples taken by Surber and kick methods from a lotic system in south-western Australia. Eleven sites were sampled concurrently in winter, spring and summer 1987.Surber samples contained fewer individuals and more taxa, particularly those with a low frequency of occurrence. This was attributed to the lower surface area, but greater intensity of Surber sampling. It is proposed that the Surber method is more suited to taking cryptic and closely adherent taxa in sites with a highly heterogeneous substratum.Percentage similarity between paired Surber and kick samples was determined by Sorensen's and Czekanowski's coefficients, with mean values of 66% and 60% for June, 61% and 49% for September and 66% and 49% for December respectively. Ordination demonstrated a division of upland from lowland sites on axis 1, with a separation of paired-samples on axis 2. This pattern held across qualitative and quantitative datasets, with and without a downweighting on rare taxa. At each level of classification fewer paired-samples separated in qualitative than quantitative datasets.Kick sampling provided a substantial saving in costs over Surber sampling, particularly when qualitative data were utilised, making the method suitable for routine, biological monitoring. However, the initial use of replicated Surber sampling, particularly in areas that have not been previously sampled is recommended for environmental impact studies to detect rare taxa, that may be endangered.     

The impact of rare taxa on a fish index of biotic integrity

The index of biotic integrity (IBI) is a commonly used bioassessment tool that integrates abundance and richness measures to assess water quality. In developing IBIs that are both responsive to human disturbance and resistant to natural variability and sampling error, water managers must decide how to weigh information about rare and abundant taxa, which in turn requires an understanding of the sensitivity of indices to rare taxa. Herein, we investigated the influence of rare fish taxa (within the lower 5% of rank abundance curves) on IBI metric and total scores for stream sites in two of Minnesota's major river basins, the St. Croix (n = 293 site visits) and Upper Mississippi (n = 210 site visits). We artificially removed rare taxa from biological samples by (1) separately excluding each individual taxon that fell within the lower 5% of rank abundance curves; (2) simultaneously excluding all taxa that had an abundance of one (singletons) or two (doubletons); and (3) simultaneously excluding all taxa that fell within the lower 5% of rank abundance curves. We then compared IBI metric and total scores before and after removal of rare taxa using the normalized root mean square error (nRMSE) and regression analysis. The difference in IBI metric and total scores increased as more taxa were removed. Moreover, when multiple rare taxa were removed, the nRMSE was related to sample abundance and to total taxa richness, with greater nRMSE observed in samples with a larger number of taxa or sample abundance. Metrics based on relative abundance of fish taxa were less sensitive to the loss of rare taxa, whereas those based on taxa richness were more sensitive, because taxa richness metrics give more weight to rare taxa compared to the relative abundance metrics.     

Remote sensing improves prediction of tropical montane species diversity but performance differs among taxa

Texture information from passive remote sensing images provides surrogates for habitat structure, which is relevant for modeling biodiversity across space and time and for developing effective ecological indicators. However, the applicability of this information might differ among taxa and diversity measures. We compared the ability of indicators developed from texture analysis of remotely sensed images to predict species richness and species turnover of six taxa (trees, pyraloid moths, geometrid moths, arctiinae moths, ants, and birds) in a megadiverse Andean mountain rainforest ecosystem. Partial least-squares regression models were fitted using 12 predictors that characterize the habitat and included three topographical metrics derived from a high-resolution digital elevation model and nine texture metrics derived from very high-resolution multi-spectral orthophotos. We calculated image textures derived from mean, correlation, and entropy statistics within a relatively broad moving window (102 m × 102 m) of the near infra-red band and two vegetation indices. The model performances of species richness were taxon dependent, with the lowest predictive power for arctiinae moths (4%) and the highest for ants (78%). Topographical metrics sufficiently modeled species richness of pyraloid moths and ants, while models for species richness of trees, geometrid moths, and birds benefited from texture metrics. When more complexity was added to the model such as additional texture statistics calculated from a smaller moving window (18 m × 18 m), the predictive power for trees and birds increased significantly from 12% to 22% and 13% to 27%, respectively. Gradients of species turnover, assessed by non-metric two-dimensional scaling (NMDS) of Bray-Curtis dissimilarities, allowed the construction of models with far higher predictability than species richness across all taxonomic groups, with predictability for the first response variable of species turnover ranging from 64% (birds) to 98% (trees) of the explained change in species composition, and predictability for the second response variable of species turnover ranging from 33% (trees) to 74% (pyraloid moths). The two NMDS axes effectively separated compositional change along the elevational gradient, explained by a combination of elevation and texture metrics, from more subtle, local changes in habitat structure surrogated by varying combinations of texture metrics. The application of indicators arising from texture analysis of remote sensing images differed among taxa and diversity measures. However, these habitat indicators improved predictions of species diversity measures of most taxa, and therefore, we highly recommend their use in biodiversity research.     

Temporal dynamics of benthic macroinvertebrate communities and their response to elevated specific conductance in Appalachian coalfield headwater streams

Coal mining in central Appalachia USA causes increased specific conductance in receiving streams. Researchers have examined benthic macroinvertebrate community structure in such streams using temporally discrete measurements of SC and benthic macroinvertebrates; however, both SC and benthic macroinvertebrate communities exhibit intra-annual variation. Twelve central Appalachian headwater streams with reference quality physical habitat and physicochemical conditions (except for elevated SC in eight streams) were sampled ≤fourteen times each between June 2011 and November 2012 to evaluate benthic macroinvertebrate community structure. Specific conductance was recorded at each sampling event and by in situ data loggers. Streams were classified by mean SC Level (Reference, 17–142 μS/cm; Medium, 262–648 μS/cm; and High, 756–1535 μS/cm). Benthic macroinvertebrate community structure was quantified using fifteen metrics selected to characterize community composition and presence of taxa from orders Ephemeroptera, Plecoptera, and Trichoptera. Metrics were analyzed for differences among SC Levels and months of sampling. Reference streams differed significantly from Medium-SC and High-SC streams for 11 metrics. Medium-SC streams had the most metrics exhibiting significant differences among months. Relative abundances of Plecoptera and Trichoptera were not sensitive to SC, as the families Leuctridae and Hydropsychidae exhibited increased relative abundance (vs. reference) in streams with elevated SC. In contrast, Ephemeroptera richness and relative abundance were lower, relative to reference, in elevated-SC streams despite increased relative abundance of Baetidae. Temporal variability was evident in several metrics due to influence by taxa with seasonal life cycles. These results demonstrate that benthic macroinvertebrate communities in elevated-SC streams are altered from reference condition, and that metrics differ in SC sensitivity. The time of year when samples are taken influenced measured levels and differences from reference condition for most metrics.     

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.     

Lake macroinvertebrate assemblages and relationship with natural environment and tourism stress in Jiuzhaigou Natural Reserve,China

With increasing human population and urbanization, tourism in natural reserves and other protected lands is growing. It is critical to monitor and assess the impacts of tourism on ecosystem health. However, there is a general lack of information on biological communities in natural reserves of developing countries and of tools for assessing human impacts. In the present study, we investigated macroinvertebrate assemblages in nine lakes in Jiuzhaigou Natural Reserve of China. Both benthic (20 dips of D-net) and light-trap samples (2 h) were collected at each lake and all benthic specimens and adults of Ephemeroptera, Plecoptera, and Trichoptera (EPT) were identified and counted. Water temperature and water quality variables were measured on site or in the Lab. Seventy taxa were recorded and dominated by dipterans and caddisflies. Light traps contributed 47% of taxa richness and 66% of EPT richness at the lakes. Detrended Correspondence Analysis showed that water temperature and tourism index were strongly associated with the changes of assemblage composition. Taxa richness and EPT richness calculated for the composite samples (benthic + light trap) were well fit with Poisson generalized linear model (adjusted R² = 0.83 and 0.85, respectively), generally decreasing with increasing elevation, tourism index, and total-N. Tourism index was ranked as the top predictor for EPT richness based on multiple model weights, and elevation for taxa richness. In comparison, when based on benthic samples, neither of the metrics could be fitted with the seven environmental variables selected. These findings highlight the benefit of combined use of the sampling methods for lake monitoring and offered an analytical guide to developing biological indicators of lake ecosystem health in protected areas.     

Temporal stability of vegetation indicators of wetland condition

Vegetation indices are widely employed to evaluate wetland ecological condition, and are expected to provide sensitive and specific detection of environmental change. Most studies evaluate the performance of condition assessment metrics in the context of the data used to calibrate them. Here we examined the temporal stability of the Florida Wetland Condition Index (FWCI) for vegetation of depressional forested wetlands by resampling sites in 2008 that were previously sampled to develop the FWCI in 2001. Our objective was to determine if FWCI, a composite of six vegetation-based metrics, provides a robust measure of condition given inter-annual variation in environmental conditions (i.e., rainfall) between sampling periods. To that end, we sampled 22 geographically isolated wetlands in north Florida that spanned a wide land use/land cover intensity gradient. Our results suggested the FWCI is robust. We observed no significant paired difference in FWCI across or within land use categories, and the relationship between FWCI in 2001 and 2008 was strong (r² = 0.88, p < 0.001). This was despite surprisingly high composition change. Mean Jaccard community similarity within sites between years was 0.30, suggesting that most of the herbaceous taxa were replaced, possibly because of different antecedent rainfall conditions or sampling during different phenological periods; both are contingencies to which condition indices must be robust. We did observe some evidence of convergence toward the mean in 2008, with the fitted slope relating 2001 and 2008 FWCI scores significantly below one (0.63, 95% CI = 0.53–0.73). The most variable FWCI component metric was the proportional representation of obligate wetland taxa, suggesting that systematic changes may have been induced by different hydrologic conditions prior to sampling; notably, however, FWCI computed without this component still exhibited a slope significantly less than 1 (0.72, 95% CI = 0.61–0.88). Moreover, there was evidence that species lost from reference sites (higher condition) were replaced by taxa of lower floristic quality, while species lost from agricultural sites (consistently the lowest condition land use category) were replaced by species of higher quality. A significant positive association between FWCI and the ratio of coefficients of conservatism (CC) of species lost to those gained suggests some overfitting in FWCI development. However, despite modest evidence of overfitting, FWCI provides temporally consistent estimates of wetland condition, even under conditions of substantial taxonomic turnover.     

Isotopic metrics as a tool for assessing the effects of mine pollution on stream food webs

Most tools used to assess pollution impacts are based on structural, or less frequently, functional aspects of biotic communities. However, the application of measures that take a food web approach to understand the effects of stress on stream ecosystems offers a new perspective and promising insights. We assessed quantitative isotopic metrics, which describe characteristics of food web structure, as indicators of acid mine drainage (AMD) in 12 streams along a stress gradient and compared these metrics with traditional structural and functional metrics. The gradient ranged from highly stressed (pH < 3) streams with elevated concentrations of dissolved metals (Fe and Al) to moderately acidic streams (pH 3.6–4.9) with substrata coated in metal hydroxide precipitates and circumneutral reference streams. Key differences in food web structure were detected by the isotopic metrics. Specifically, fewer trophic levels and reduced trophic diversity characterized food webs in all mining impacted streams but the differences were not significant along the gradient. In contrast, most structural and functional metrics were significant predictors of AMD as stress increased. Therefore, our results suggest that isotopic metrics offer little advantage over traditional metrics in terms of detecting impacts for biomonitoring purposes. However, they do provide additional insights into how whole food webs are disrupted, and are likely to be more useful for guiding stream management and rehabilitation strategies.     

Evaluation of stream ecosystem health and species association based on multi-taxa (benthic macroinvertebrates,algae, and microorganisms) patterning with different levels of pollution

Benthic communities of macroinvertebrates, algae, and microorganisms were concurrently collected using a Surber sampler (30 × 30 m²; 300 μm mesh), brush (5 × 5 cm²), and syringe (100 mL; Denaturing Gradient Gel Electrophoresis), respectively, to determine the ecological integrity of streams with different levels of pollution. Macroinvertebrates provided a clearer representation of the gradient of pollution, while a broader scope of species distribution was observed for algae and microorganisms, including sites severely polluted with heavy metals. Species associations among different taxa were presented on the Self-Organizing Map (SOM) and Nonmetric Multidimensional Scaling (NMDS) based on environmental factors. After screening, indicator species visualized on the SOM represented a wider range of environmental impacts and were more illustrative with benthic macroinvertebrates in least polluted sites. In contrast NMDS presented species more closely associated with overall variance of communities with severe pollution, mainly in microorganisms and algae. Multi-taxa community analysis using SOM and NMDS in combination would provide a comprehensive assessment for addressing ecological integrity in streams.     

Toward a practical use of Neotropical odonates as bioindicators: Testing congruence across taxonomic resolution and life stages

Odonates are suggested as bioindicators of human impact. However, their complex life cycles add additional challenges in the practical use as bioindicators, because the level of taxonomic identification could be dependent on life-history stage and, during their ontogeny, dramatic changes occur in their niche (ontogenetic niche shifts). Considering that larvae and adults have different biological characteristics, which could interfere in their performance as bioindicators, we first sought to understand how similar or different environmental factors affect larval and adult life stages in the Odonata. Second, we assessed the level of congruence between (larvae and adult) and within (adult genera and species) life-history stages, considering the taxonomic and numerical resolution. We sampled larvae and adults in 44 streams distributed along a riverine network in southwest Brazil. Larvae samples constituted 20 sampling units of 1 m length each, using the kick sampling method; adults were collected for 1 h at each site with a hand net along a 100-m transect parallel to the stream/river banks. The influence of environmental factors on larvae and adult was assessed by redundancy analysis coupled with forward selection. The congruence level between response matrices was determined by Procrustes analysis. Our results revealed that a set of environmental variables explained a portion of larvae and adults distribution and some environmental factors affect both between (larvae and adults) and within (adult genera and species) life-history stages. Larvae and adult were about 54% congruent, regardless of taxonomic level of adults. Abundance of adult genera and species were 94% congruent, but numerical resolution (abundance vs. incidence) decreased the congruency by 10%. Environmental variables could influence larvae and adults individually or via carry-over effects, i.e., larval environmental conditions that could affect adult fitness components or vice versa. In addition, some odonate behaviors, such as female selection of more appropriate habitats for laying their eggs, could also help us to explain our results, because it could determine larvae distribution. In a biomonitoring perspective, considering the cost-benefit of taxonomic level and sampling of larvae and adults, our results suggest that abundance of adult genera could be used in biomonitoring programs since they capture, respectively, 94% and 54% of the information carried by adult species and larvae.     

Validating Landsat-based landscape metrics with fine-grained land cover data

ContextModerate-grained data may not always represent landscape structure in adequate detail which could cause misleading results. Certain metrics have been shown to be predictable with changes in scale; however, no studies have verified such predictions using independent fine-grained data.ObjectivesOur objective was to use independently derived land cover datasets to assess relationships between metrics based on fine- and moderate-grained data for a range of analysis extents. We focus on metrics that previous literature has shown to have predictable relationships across scales.MethodsThe study area was located in eastern Connecticut. We compared a 1 m land cover dataset to a 30 m resampled dataset, derived from the 1 m data, as well as two Landsat-based datasets. We examined 11 metrics which included cover areas and patch metrics. Metrics were analyzed using analysis extents ranging from 100 to 1400 m in radius.ResultsThe resampled data had very strong linear relationships to the 1 m data, from which it was derived, for all metrics regardless of the analysis extent size. Landsat-based data had strong correlations for most cover area metrics but had little or no correlation for patch metrics. Increasing analysis areas improved correlations.ConclusionsRelationships between coarse- and fine-grained data tend to be much weaker when comparing independent land cover datasets. Thus, trends across scales that are found by resampling land cover are likely to be unsuitable for predicting the effects of finer-scale elements in the landscape. Nevertheless, coarser data shows promise in predicting fine-grained for cover area metrics provided the analysis area used is sufficiently large.     

Substratum associations of benthic invertebrates in lowland and mountain streams

The preferences of aquatic invertebrate species for specific substrata at the river bottom have been subject of many studies. Several authors classified the substratum preferences of species or higher taxonomic units. Most of these compilations, however, are based on literature analyses and expert knowledge as opposed to the analysis of original data. To enhance our knowledge of invertebrate substratum preferences, we applied a ‘Multi-level pattern’ analysis based on almost 1000 substrate-specific invertebrate samples. The samples were taken in 18 streams in Germany, the Netherlands and Austria, comprising a total of 40 sampling sites and equally covering lowland and mountain streams. The main objectives of our analysis were (I) to derive substratum preferences of taxa in lowland and mountain streams, (II) to compare the preferences with existing data and (III) to compare species substratum associations between lowland and mountain streams. Of the 290 taxa analyzed, 188 were associated significantly to specific substrata. Twenty-five taxa in lowland streams and 51 taxa in mountain streams prefer one or two substratum types (of nine substratum types considered in total). In contrast, 112 species (mountain streams n = 84, lowland streams n = 28) are associated significantly with a broader range of substrata. We compared the classifications derived from our data analysis with those provided in the freshwaterecology.info database (www.freshwaterecology.info). Our results support the existing classifications of substratum preferences in most cases (70%). For 25 species, substratum preferences for both lowland and mountain streams were derived, many of them indicating different substratum associations in the two stream groups. As substratum preferences differed between closely related species, preferences should always be given at the species level as opposed to coarser taxonomic units.     

Using algal metrics and biomass to evaluate multiple ways of defining concentration-based nutrient criteria in streams and their ecological relevance

We examined the utility of nutrient criteria derived solely from total phosphorus (TP) concentrations in streams (regression models and percentile distributions) and evaluated their ecological relevance to diatom and algal biomass responses. We used a variety of statistics to characterize ecological responses and to develop concentration-based nutrient criteria (derived from ecological effects) for streams in Connecticut, USA, where urbanization is the primary cause of watershed alteration. Mean background TP concentration in the absence of anthropogenic land cover was predicted to be 0.017 mg/l, which was similar to the 25th percentile of all study sites. Increased TP concentrations were significantly correlated with altered diatom community structure, decreased percent low P diatoms and diatoms sensitive to impervious cover, and increased percent high P diatoms, diatoms that increase with greater impervious cover, and chlorophyll a (P < 0.01). Variance partitioning models showed that shared effects of anthropogenic land cover and chemistry (i.e., chemistry affected by land cover) represented the majority of explained variation in diatom metrics and chlorophyll a. Bootstrapped regression trees, threshold indicator taxa analysis, and boosted regression trees identified TP concentrations at which strong responses of diatom metrics and communities occurred, but these values varied among analyses. When considering ecological responses, scientifically defensible and ecologically relevant TP criteria were identified at (1) 0.020 mg/l for designating highest quality streams and restoration targets, above which sensitive taxa steeply declined, tolerant taxa increased, and community structure changed, (2) 0.040 mg/l, at which community level change points began to occur and sensitive diatoms were greatly reduced, (3) 0.065 mg/l, above which most sensitive diatoms were lost and tolerant diatoms steeply increased to their maxima, and (4) 0.082 mg/l, which appeared to be a saturated threshold, beyond which substantially altered community structure was sustained. These criteria can inform anti-degradation policies for high quality streams, discharge permit decisions, and future strategies for watershed development and managment. Our results indicated that management practices and decisions at the watershed scale will likely be important for improving degraded streams and conserving high quality streams. Results also emphasized the importance of incorporating ecological responses and considering the body of evidence from multiple conceptual approaches and statistical analyses for developing nutrient criteria, because solely relying on one approach could lead to misdirected decisions and resources.     

Predicted macroinvertebrate response to water diversion from a montane stream using two-dimensional hydrodynamic models and zero flow approximation

We used two-dimensional hydrodynamic models for the assessment of water diversion effects on benthic macroinvertebrates and associated habitat in a montane stream in Yosemite National Park, Sierra Nevada Mountains, CA, USA. We sampled the macroinvertebrate assemblage via Surber sampling, recorded detailed measurements of bed topography and flow, and coupled a two-dimensional hydrodynamic model with macroinvertebrate indicators to assess habitat across a range of low flows in 2010 and representative past years. We also made zero flow approximations to assess response of fauna to extreme conditions. The fauna of this montane reach had a higher percentage of Ephemeroptera, Plecoptera, and Trichoptera (%EPT) than might be expected given the relatively low faunal diversity of the study reach. The modeled responses of wetted area and area-weighted macroinvertebrate metrics to decreasing discharge indicated precipitous declines in metrics as flows approached zero. Changes in area-weighted metrics closely approximated patterns observed for wetted area, i.e., area-weighted invertebrate metrics contributed relatively little additional information above that yielded by wetted area alone. Loss of habitat area in this montane stream appears to be a greater threat than reductions in velocity and depth or changes in substrate, and the modeled patterns observed across years support this conclusion. Our models suggest that step function losses of wetted area may begin when discharge in the Merced falls to 0.02 m³/s; proportionally reducing diversions when this threshold is reached will likely reduce impacts in low flow years.     

Quantile regression analysis as a predictive tool for lake macroinvertebrate biodiversity

The Water Framework Directive introduced in Europe major changes to improve the management of water resources. This study aims to highlight some of the potential implications of its implementation for lake water monitoring in Italy. A Life+ project was launched to plan the first monitoring of lake macroinvertebrates standardized at the national level.Quantile regression analysis was used to explain different metrics of diversity describing macroinvertebrate communities in response to twenty-one variables representing chemical, physical and morphological characteristics of the environment. Nine lakes located in two Italian regions (Piedmont and Sardinia) were analyzed covering a wide trophic spectrum, from oligotrophy to hyper-eutrophy. The lakes were sampled following the national standardized protocol with samples covering the three recognized lake zones: littoral, sublittoral, profundal.The studied lakes had high chemical variability with conductivity ranging between 53 and 561 μS/cm, pH between 6.5 and 9.1, and alkalinity between 14 and 398 mg/l. The bottom sediments were characterized by fine sand (range 51–99%), followed by silt (1–35%) and clay (0–28%). When the Lake Habitat Survey was also applied to these lakes, its synthetic indices (LHMS, Lake Habitat Modification Score and LHQA, Lake Habitat Quality Assessment) produced higher values in natural lakes (mean values ± SD: LHMS = 26 ± 7, LHQA = 57 ± 3) than in the reservoirs (LHMS = 22 ± 4, LHQA = 52 ± 6). In all lakes, macroinvertebrates mainly consisted of chironomids and oligochaetes characterized by relative abundances up to 80% and >90%, respectively.Using quantile regression to evaluate limiting responses, only two variables, namely sampling depth and oxygen percent saturation (oxygen content), resulted the ones that best explained all the analyzed metrics of diversity of the macroinvertebrate communities. Depth and oxygen were then used to suggest synthetic models describing the various metrics of potential community diversity. These models can help the environmental agencies responsible for monitoring at the national level in distinguishing entire lakes or part of them with high biodiversity from those in altered conditions and then address remediation efforts toward the water bodies with the most critical conditions. Such approach could also be used to optimize the sampling procedures for the application of the Benthic Quality Index for lakes currently adopted at national level.     

Reference diatom assemblage response to restoration of an acid mine drainage stream

A prevalent legacy of coal mining within Appalachia and elsewhere is acid mine drainage (AMD), which drastically alters both the chemical and biological components of the receiving waters. Hewett Fork is one such affected stream. Although AMD treatment has reduced acidity considerably downstream, the ability of this stream to sustain a biological community compared to those found in reference conditions remains unclear. To assess this, tiles colonized with diatom assemblages from a reference stream were transplanted into Hewett Fork in 5 locations along a 6.9 km stream length and sampled after one, three, and six weeks. Diatom assemblage structure metrics, including species evenness (J’), species richness (S), relative abundance of dominant taxon, and Shannon diversity (H′), as well as chlorophyll a concentrations, Bray–Curtis dissimilarities, and Acid Mine Drainage Diatom Index of Biotic Integrity (AMD-DIBI) scores were calculated for each site and sampling time. One-way ANOVAs of structural metrics showed significant differences (P ≤ 0.001) between the reference site and the 2nd and 3rd most upstream sites within the study reach for the duration of the study, with the exception of the relative abundance of dominant taxa at an intermediate site during the third week. Conversely, the most downstream Hewett Fork assemblage, located 11.6 km from the primary AMD input, did not differ significantly (P > 0.05) from that of the reference assemblage for any structural metrics after the initial sampling period. Throughout the study, only three sites obtained “good” AMD-DIBI narrative class:the reference site (weeks 1, 3, and 6), the most downstream site (weeks 1, 3, and 6; 11.6 km downstream of primary AMD input) and the uppermost site (weeks 1 and 6; 4.7 km downstream of primary AMD input). Results suggested that after an initial one-week acclimation period, assemblages at the uppermost and most downstream sites along the reach were relatively similar to those found in reference conditions, while sites within the middle region continued to show signs of impairment, although the factor(s) causing this impairment remain unknown. These findings suggest that while treatment has been effective on a site-specific basis, the expected linear-response to treatment was not achieved due to underlying factors that are inhibiting reference-like biological communities from reestablishing within the affected stream reach.     

A sediment-specific family-level biomonitoring tool to identify the impacts of fine sediment in temperate rivers and streams

Anthropogenic modifications of sediment load can cause ecological degradation in stream and river ecosystems. However, in practice, identifying when and where sediment is the primary cause of ecological degradation is a challenging task. Biological communities undergo natural cycles and variation over time, and respond to a range of physical, chemical and biological pressures. Furthermore, fine sediments are commonly associated with numerous other pressures that are likely to influence aquatic biota. The use of conventional, non-biological monitoring to attribute cause and effect would necessitate measurement of multiple parameters, at sufficient temporal resolution, and for a significant period of time. Biomonitoring tools, which use low-frequency measurements of biota to gauge and track changes in the environment, can provide a valuable alternative means to detecting the effects of a given pressure. In this study, we develop and test an improved macroinvertebrate, family-level and mixed-level biomonitoring tool for fine sediment. Biologically-based classifications of sediment sensitivity were supplemented by using empirical data of macroinvertebrate abundance and percentage fine sediment, collected across a wide range of temperate river and stream ecosystems (model training dataset n = 2252) to assign detailed individual sensitivity weights to taxa. An optimum set of weights were identified by non-linear optimisation, as those that resulted in the highest Spearman’s rank correlation coefficient between the index (called the Empirically-weighted Proportion of Sediment-sensitive Invertebrates index; E-PSI) scores and deposited fine sediment in the model training dataset. The family and mixed-level tools performed similarly, with correlations with percentage fine sediment in the test dataset (n = 84) of r_s = −0.72 and r_s = −0.70 p < 0.01. Testing of the best performing family level version, over agriculturally impacted sites (n = 754) showed similar correlations to fine sediment (r_s = −0.68 p < 0.01). The tools developed in this study have retained their biological basis, are easily integrated into contemporary monitoring agency protocols and can be applied retrospectively to historic datasets. Given the challenges of non-biological conventional monitoring of fine sediments and determining the biological relevance of the resulting data, a sediment-specific biomonitoring approach is highly desirable and will be a useful addition to the suite of pressure-specific biomonitoring tools currently used to infer the causes of ecological degradation.     

The Biological Sediment Tolerance Index: Assessing fine sediments conditions in Oregon streams using macroinvertebrates

Fine sediments in excess of natural background conditions are one of most globally common causes of stream degradation, with well documented impacts on aquatic communities. The lack of agreement on methods for monitoring fine sediments makes it difficult to share data, limiting assessments of stream conditions across jurisdictions. We present a model that circumvents these limitations by inferring fine sediments in Oregon streams through sampling of macroinvertebrates. Tolerances to fine sediments (<0.06 mm diameter) were calculated for 240 macroinvertebrate taxa, from a calibration dataset of 446 sites across Oregon, as well as an independent validation dataset of 50 samples. Weighted averaging methods were used to infer fine sediment levels in streams by weighting the tolerances of modeled taxa observed in a sample by their abundances. The final model, the Biological Sediment Tolerance Index (BSTI), showed a strong relationship to measured fine sediments (calibration r² = 0.49, validation r² = 0.58). Root-mean-squared-error was small in the calibration dataset (2% fines), but larger in the validation dataset (14% fines). Repeatability was assessed by examining variability in BSTI at 14 sites across Oregon. Because field methods for sampling macroinvertebrates are standardized across resource agencies in Oregon and the responses of macroinvertebrates represent the actual effects of fine sediments on stream ecosystems, the BSTI may offer water resource managers’ a cost-effective method for assessing fine sediment conditions in their ongoing efforts to improve water quality across the state.     

Spatial factors contribute to benthic diatom structure in streams across spatial scales: Considerations for biomonitoring

Diatoms are widely used in the biological monitoring of streams because they are strong responders to environmental change, but dispersal and spatial factors can play important and potentially confounding roles in the presence, absence, and abundance of species along with characterizing species–environment relationships. To examine how spatial factors affect diatom community structure and biomonitoring, multiple scales were sampled including the Western Allegheny Plateau (n = 58), Leading Creek watershed (n = 18), and the adjacent Shade River watershed (n = 21) in southeast Ohio. Partitioning of spatial, environmental, and spatially-structured environmental variation was conducted on diatom assemblages and on diatom metrics used in biomonitoring. At the regional scale, diatom assemblages and metrics had strong relationships with agricultural (e.g., significant correlations with nutrients, conductivity, and pasture/row crops in the watershed) and alkalinity gradients. Diatom assemblages and metrics in both watersheds were strongly associated with acid mine drainage (AMD) impacts, and when spatial factors were set as covariables in CCAs, relationships with AMD gradients became even stronger, indicating the need to consider how spatial factors could reduce the strength of diatom-environment relationships. Metrics calculated at all scales had very little variation explained exclusively by spatial factors, likely because multiple species are combined into a simplified metric that reduces the effects of species dispersal. Local environmental variables accounted for 57, 42, and 42% of the total variation explained (TVE), and spatial variables accounted for 28, 31, and 37% of the TVE in the regional, Leading Creek, and Shade River datasets, respectively. The amounts of variation in diatom assemblages explained solely by spatial factors at these scales were substantial and similar to what has been reported at continental, national, and large regional (Level I Omernik ecoregions) scales (approximately 1/3 of TVE). Although amounts of variation explained are similar across scales, processes underlying the spatial structure likely differ. In addition to describing ecological patterns, recognizing the potential influence of spatial factors could improve the identification and management of environmental problems at a range of scales, as well as aid in the development of new research questions and hypotheses aimed at exploring factors that could explain portions of the spatially explicit variation.     

Mayfly bioindicator thresholds for several anthropogenic disturbances in neotropical savanna streams

Anthropogenic disturbances are widely recognized as major threats to terrestrial and aquatic biodiversity worldwide, including areas located in non-forest ecosystems. Headwater streams in the neotropical savanna are severely threatened by large-scale landscape changes that degrade local habitat characteristics and lead to biodiversity loss. The objective of our study was to evaluate Ephemeroptera assemblages as bioindicators of catchment land use and cover, local streambed and riparian vegetation conditions, and instream water quality. To do so, we sampled mayfly nymphs in 184 stream sites across a broad disturbance gradient in four hydrologic units of the Brazilian neotropical savanna. We selected seven metrics without significant co-variation with natural variability: % catchment urban, riparian vegetation condition index (RCOND), human disturbances of the stream channel and riparian zone (W1_HALL), substrate mean embeddedness (XEMBED), dissolved oxygen (mg L⁻¹), pH, and total phosphorus (mg L⁻¹). We ran threshold indicator taxa analysis (TITAN) for each disturbance metric to detect change points in mayfly genera responses (whether sensitive or tolerant) and assemblage turnover pattern. TITAN showed that 20 of the 39 genera found were robust bioindicators (based on purity and reliability values >0.95), sixteen of them being sensitive to increased disturbance. The most sensitive genera were Tricorythopsis (Leptohyphidae) and Camelobaetidius (Baetidae), showing decreased abundance to most disturbance metrics. We found a turnover pattern of mayfly genera in response to W1_HALL in a narrow variation range. For total phosphorus, the benchmark value defined in Brazilian Federal Legislation is higher than the turnover threshold of several mayfly genera. This indicates that we will lose many sensitive genera even within the limits imposed by national environmental legislation. The indicator taxa approach, based on multiple taxa rather than univariate metrics or single indicator species, demonstrates the value of quantitative ecological information for conserving and managing freshwater ecosystems globally.