The Relation of Lotic Fish and Benthic Macroinvertebrate Condition Indices to Environmental Factors Across the Conterminous USA

Multiple lines of evidence point to pesticides as stressors affecting invertebrate communities in small streams in five United States regions

Multistressor studies were performed in five regions of the United States to assess the role of pesticides as stressors affecting invertebrate communities in wadable streams. Pesticides and other chemical and physical stressors were measured in 75 to 99 streams per region for 4 weeks, after which invertebrate communities were surveyed (435 total sites). Pesticides were sampled weekly in filtered water, and once in bed sediment. The role of pesticides as a stressor to invertebrate communities was assessed by evaluating multiple lines of evidence: toxicity predictions based on measured pesticide concentrations, multivariate models and other statistical analyses, and previously published mesocosm experiments. Toxicity predictions using benchmarks and species sensitivity distributions and statistical correlations suggested that pesticides were present at high enough concentrations to adversely affect invertebrate communities at the regional scale. Two undirected techniques-boosted regression tree models and distance-based linear models-identified which pesticides were predictors of (respectively) invertebrate metrics and community composition. To put insecticides in context with known, influential covariates of invertebrate response, generalized additive models were used to identify which individual pesticide(s) were important predictors of invertebrate community condition in each region, after accounting for natural covariates. Four insecticides were identified as stressors to invertebrate communities at the regional scale: bifenthrin, chlordane, fipronil and its degradates, and imidacloprid. Fipronil was particularly important in the Southeast region, and imidacloprid, bifenthrin, and chlordane were important in multiple regions. For imidacloprid, bifenthrin, and fipronil, toxicity predictions were supported by mesocosm experiments that demonstrated adverse effects on naïve aquatic communities when dosed under controlled conditions. These multiple lines of evidence do not prove causality-which is challenging in the field under multistressor conditions-but they make a strong case for the role of insecticides as stressors adversely affecting invertebrate communities in streams within the five sampled regions.

Omernik's Ecoregion Framework: a Legacy for Understanding Regional Patterns in Attainable Resource Quality

An initial and comprehensive map of ecological regions across the conterminous United States was provided by Omernik in 1987. Because that paper was the most-cited published by the Annals of the American Association of Geographers, we sought to assess and quantify its contribution to science. To do so, we conducted a scientometric analysis to address the following main questions: 1) What are the temporal and spatial citation trends? We expected that Omernik's paper would still be employed 36 years after its publication, and mostly in the United States of America. 2) For what types of environments and organisms has it been applied? Based on its generality, we expected that it had been applied to both terrestrial and aquatic ecosystems. 3) What are the main applications of Omernik's article? We predicted that it would mostly be used for describing and delineating study sites and management areas, as well as for selecting regional reference sites. The number of citations presented a positive temporal increase, indicating its continued applicability. Most papers dealt with aquatic environments, mainly in streams carried out predominantly in the United States of America, as was one of its earliest applications. The usefulness of ecoregions for assessing and managing biotic and abiotic patterns and distributions were the main topics addressed by scientists. Ecoregions have offered a general framework for developing regional expectations and rational regional management policies across large areas, as was their original intent. In addition, ecoregion maps were used for communicating patterns-or the lack of them-to interested scientists, citizens, and decision-makers. That comprehensiveness of Omernik's ecoregion approach has led to its widespread applicability and continued usefulness to a diverse set of scientific and management disciplines.

Water quality deterioration remains a major stressor for macroinvertebrate, diatom and fish communities in German rivers

About 60 % of Europe's rivers fail to meet ecological quality standards derived from biological criteria. The causes are manifold, but recent reports suggest a dominant role of hydro-morphological and water quality-related stressors. Yet, in particular micropollutants and hydrological stressors often tend to be underrepresented in multiple-stressor studies. Using monitoring data from four Federal States in Germany, this study investigated the effects of 19 stressor variables from six stressor groups (nutrients, salt ions, dissolved oxygen/water temperature, mixture toxicity of 51 micropollutants, hydrological alteration and morphological habitat quality) on three biological assemblages (fishes, macroinvertebrates, benthic diatoms). Biological effects were analyzed for 35 community metrics and quantified using Random Forest (RF) analyses to put the stressor groups into a hierarchical context. To compare metric responses, metrics were grouped into categories reflecting important characteristics of biological communities, such as sensitivity, functional traits, diversity and community composition as well as composite indices that integrate several metrics into one single index (e.g., ecological quality class). Water quality-related stressors - but not micropollutants - turned out to dominate the responses of all assemblages. In contrast, the effects of hydro-morphological stressors were less pronounced and stronger for hydrological stressors than for morphological stressors. Explained variances of RF models ranged 23-64 % for macroinvertebrates, 16-40 % for benthic diatoms and 18-48 % for fishes. Despite a high variability of responses across assemblages and stressor groups, sensitivity metrics tended to reveal stronger responses to individual stressors and a higher explained variance in RF models than composite indices. The results of this study suggest that (physico-chemical) water quality deterioration continues to impact biological assemblages in many German rivers, despite the extensive progress in wastewater treatment during the past decades. To detect water quality deterioration, monitoring schemes need to target relevant physico-chemical stressors and micropollutants. Furthermore, monitoring needs to integrate measures of hydrological alteration (e.g., flow magnitude and dynamics). At present, hydro-morphological surveys rarely address the degree of hydrological alteration. In order to achieve a good ecological status, river restoration and management needs to address both water quality-related and hydro-morphological stressors. Restricting analyses to just one single organism group (e.g., macroinvertebrates) or only selected metrics (e.g., ecological quality class) may hamper stressor identification and its hierarchical classification and, thus may mislead river management.

Patterns in and predictors of stream and river macroinvertebrate genera and fish species richness across the conterminous USA

Both native and non-native taxa richness patterns are useful for evaluating areas of greatest conservation concern. To determine those patterns, we analyzed fish and macroinvertebrate taxa richness data obtained at 3475 sites collected by the USEPA's National Rivers and Streams Assessment. We also determined which natural and anthropogenic variables best explained patterns in regional richness. Macroinvertebrate and fish richness increased with the number of sites sampled per region. Therefore, we determined residual taxa richness from the deviation of observed richness from predicted richness given the number of sites per region. Regional richness markedly exceeded average site richness for both macroinvertebrates and fish. Predictors of macroinvertebrate-genus and fish-species residual-regional richness differed. Air temperature was an important predictor in both cases but was positive for fish and negative for macroinvertebrates. Both natural and land use variables were significant predictors of regional richness. This study is the first to determine mean site and regional richness of both fish and aquatic macroinvertebrates across the conterminous USA, and the key anthropogenic drivers of regional richness. Thus, it offers important insights into regional USA biodiversity hotspots.

Observed and projected functional reorganization of riverine fish assemblages from global change

Climate and land-use/land-cover change ("global change") are restructuring biodiversity, globally. Broadly, environmental conditions are expected to become warmer, potentially drier (particularly in arid regions), and more anthropogenically developed in the future, with spatiotemporally complex effects on ecological communities. We used functional traits to inform Chesapeake Bay Watershed fish responses to future climate and land-use scenarios (2030, 2060, and 2090). We modeled the future habitat suitability of focal species representative of key trait axes (substrate, flow, temperature, reproduction, and trophic) and used functional and phylogenetic metrics to assess variable assemblage responses across physiographic regions and habitat sizes (headwaters through large rivers). Our focal species analysis projected future habitat suitability gains for carnivorous species with preferences for warm water, pool habitats, and fine or vegetated substrates. At the assemblage level, models projected decreasing habitat suitability for cold-water, rheophilic, and lithophilic individuals but increasing suitability for carnivores in the future across all regions. Projected responses of functional and phylogenetic diversity and redundancy differed among regions. Lowland regions were projected to become less functionally and phylogenetically diverse and more redundant while upland regions (and smaller habitat sizes) were projected to become more diverse and less redundant. Next, we assessed how these model-projected assemblage changes 2005-2030 related to observed time-series trends (1999-2016). Halfway through the initial projecting period (2005-2030), we found observed trends broadly followed modeled patterns of increasing proportions of carnivorous and lithophilic individuals in lowland regions but showed opposing patterns for functional and phylogenetic metrics. Leveraging observed and predicted analyses simultaneously helps elucidate the instances and causes of discrepancies between model predictions and ongoing observed changes. Collectively, results highlight the complexity of global change impacts across broad landscapes that likely relate to differences in assemblages' intrinsic sensitivities and external exposure to stressors.

The impact of land use on stream macroinvertebrates: a bibliometric analysis for 2010-2021

Changes in stream biodiversity are now mainly driven by land-use development. However, a literature review on the impact of land use on stream macroinvertebrates is lacking, especially a scientometric review. Here, we bibliometrically analyzed the literature on land use and stream macroinvertebrates that were published in 2010-2021 and listed in the Web of Science database. We found that the impact of land use on stream macroinvertebrates had been increasingly studied and that these studies were distributed across the globe and had multi-national collaborations. Through co-citation analysis and high-frequency keyword analysis, we found that land use and some environmental factors, especially water quality and habitat, affected macroinvertebrate community biodiversity, biotic integrity, and patterns. Macroinvertebrate traits, analytical methods or models, evaluation index development, and riparian vegetation were the research hotspots. Using historical direct citation network analysis, we also found that the analytical methods in this field and the macroinvertebrate evaluation index had clear development trends from 2010 to 2021. Our findings can help researchers quickly grasp the background of the impact of land use on stream macroinvertebrates and inform future research.

Fish and macroinvertebrate assemblages reveal extensive degradation of the world's rivers

Rivers suffer from multiple stressors acting simultaneously on their biota, but the consequences are poorly quantified at the global scale. We evaluated the biological condition of rivers globally, including the largest proportion of countries from the Global South published to date. We gathered macroinvertebrate- and fish-based assessments from 72,275 and 37,676 sites, respectively, from 64 study regions across six continents and 45 nations. Because assessments were based on differing methods, different systems were consolidated into a 3-class system: Good, Impaired, or Severely Impaired, following common guidelines. The proportion of sites in each class by study area was calculated and each region was assigned a Köppen-Geiger climate type, Human Footprint score (addressing landscape alterations), Human Development Index (HDI) score (addressing social welfare), % rivers with good ambient water quality, % protected freshwater key biodiversity areas; and % of forest area net change rate. We found that 50% of macroinvertebrate sites and 42% of fish sites were in Good condition, whereas 21% and 29% were Severely Impaired, respectively. The poorest biological conditions occurred in Arid and Equatorial climates and the best conditions occurred in Snow climates. Severely Impaired conditions were associated (Pearson correlation coefficient) with higher HDI scores, poorer physico-chemical water quality, and lower proportions of protected freshwater areas. Good biological conditions were associated with good water quality and increased forested areas. It is essential to implement statutory bioassessment programs in Asian, African, and South American countries, and continue them in Oceania, Europe, and North America. There is a need to invest in assessments based on fish, as there is less information globally and fish were strong indicators of degradation. Our study highlights a need to increase the extent and number of protected river catchments, preserve and restore natural forested areas in the catchments, treat wastewater discharges, and improve river connectivity.

Physical habitat in conterminous US streams and Rivers, part 2: A quantitative assessment of habitat condition

Rigorous assessments of the ecological condition of water resources and the effect of human activities on those waters require quantitative physical, chemical, and biological data. The U.S. Environmental Protection Agency's river and stream surveys quantify river and stream bed particle size and stability, instream habitat complexity and cover, riparian vegetation cover and structure, and anthropogenic disturbance activities. Physical habitat is strongly controlled by natural geoclimatic factors that co-vary with human activities. We expressed the anthropogenic alteration of physical habitat as O/E ratios of observed habitat metric values divided by values expected under least-disturbed reference conditions, where site-specific expected values vary given their geoclimatic and geomorphic context. We set criteria for good, fair, and poor condition based on the distribution of O/E values in regional least-disturbed reference sites. Poor conditions existed in 22-24% of the 1.2 million km of streams and rivers in the conterminous U.S. for riparian human disturbance, streambed sediment and riparian vegetation cover, versus 14% for instream habitat complexity. Based on the same four indicators, the percentage of stream length in poor condition within 9 separate U.S. ecoregions ranged from 4% to 42%. Associations of our physical habitat indices with anthropogenic pressures demonstrate the scope of anthropogenic habitat alteration; habitat condition was negatively related to the level of anthropogenic disturbance nationally and in nearly all ecoregions. Relative risk estimates showed that streams and rivers with poor sediment, riparian cover complexity, or instream habitat cover conditions were 1.4 to 2.6 times as likely to also have fish or macroinvertebrate assemblages in poor condition. Our physical habitat condition indicators help explain deviations in biological conditions from those observed among least-disturbed sites and inform management actions for rehabilitating impaired waters and mitigating further ecological degradation.

Genus-level, trait-based multimetric diatom indices for assessing the ecological condition of rivers and streams across the conterminous United States

Taxonomic inconsistency in species-level identifications has constrained use of diatoms as biological indicators in aquatic assessments. We addressed this problem by developing diatom multimetric indices (MMIs) of ecological condition using genus-level taxonomy and trait-based autecological information. The MMIs were designed to assess river and stream chemical, physical and biological condition across the conterminous United States. Trait-based approaches have the advantage of using both species-level and genus-level data, which require less effort and expense to acquire than traditional species-based approaches and eliminate the persistent taxonomic biases introduced over vast geographic extents. For large-extent assessment programs that require multiple taxonomic laboratories to process samples, such as the United States Environmental Protection Agency's (U.S. EPA's) National Rivers and Streams Assessment (NRSA), the trait approach can eliminate discrepancies in species-level identification or nomenclature that hinder diatom data interpretation. We developed trait-based MMIs using NRSA data for each of the three large ecoregions across the U.S. - the East, Plains, and West. All three MMIs performed well in discriminating least-disturbed from most-disturbed sites. The MMI for the East had the greatest discrimination ability, followed by MMIs for the Plains and West, respectively. The performance of the MMIs was comparable to that observed in existing NRSA fish and macroinvertebrate MMIs. Our research shows that trait-based diatom indices constructed on genus-level taxonomy can be effective for large-scale assessments, and may also allow programs such as NRSA to assess trends in freshwater condition retrospectively, by revisiting older diatom datasets. Moreover, our genus-based approach facilitates including of diatoms into other assessment programs that have limited monitoring resources.

Physical habitat in conterminous US streams and rivers, Part 1: Geoclimatic controls and anthropogenic alteration

Anthropogenic alteration of physical habitat structure in streams and rivers is increasingly recognized as a major cause of impairment worldwide. As part of their assessment of the status and trends in the condition of rivers and streams in the U.S., the U.S. Environmental Protection Agency's (USEPA) National Aquatic Resource Surveys (NARS) quantify and monitor channel size and slope, substrate size and stability, instream habitat complexity and cover, riparian vegetation cover and structure, anthropogenic disturbance activities, and channel-riparian interaction. Like biological assemblages and water chemistry, physical habitat is strongly controlled by natural geoclimatic factors that can obscure or amplify the influence of human activities. We developed a systematic approach to estimate the deviation of observed river and stream physical habitat from that expected in least-disturbed reference conditions. We applied this approach to calculate indices of anthropogenic alteration of three aspects of physical habitat condition in the conterminous U.S. (CONUS): streambed sediment size and stability, riparian vegetation cover, and instream habitat complexity. The precision and responsiveness of these indices led the USEPA to use them to evaluate physical habitat condition in CONUS rivers and streams. The scores of these indices systematically decreased with greater anthropogenic disturbance at river and stream sites in the CONUS and within ecoregions, which we interpret as a response of these physical habitat indices to anthropogenic influences. Although anthropogenic activities negatively influenced all three physical habitat indices in the least-disturbed sites within most ecoregions, natural geoclimatic and geomorphic factors were the dominant influences. For sites over the full range of anthropogenic disturbance, analyses of observed/expected sediment characteristics showed augmented flood flows and basin and riparian agriculture to be the leading predictors of streambed instability and excess fine sediments. Similarly, basin and riparian agriculture and non-agricultural riparian land uses were the leading predictors of reduced riparian vegetation cover complexity in the CONUS and within ecoregions. In turn, these reductions in riparian vegetation cover and complexity, combined with reduced summer low flows, were the leading predictors of instream habitat simplification. We conclude that quantitative measures of physical habitat structure are useful and important indicators of the impacts of human activities on stream and river condition.

Anthropogenic land‒use impacts on the size structure of macroinvertebrate assemblages are jointly modulated by local conditions and spatial processes

Body size descriptors and associated resemblance measurements may provide useful tools for forecasting ecological responses to increasing anthropogenic land‒use disturbances. Yet, the influences of agriculture and urbanisation on the size structure of biotic assemblages have seldom been investigated in running waters. Using a comprehensive dataset on stream macroinvertebrates from 21 river basins across Western Finland, we assessed whether the structure of assemblages via changes in taxonomic composition and body size distributions responded predictably to anthropogenic land‒use impacts. Specifically, we applied a combination of resemblance measurements based on cumulative abundance profiles and spatially constrained null models to understand faunal impairment by agricultural and urban development, and the most likely mechanisms underlying the observed shifts in assemblage size structure. Anthropogenically impacted stream sites showed less variation in assemblage composition and size distributions compared with least‒disturbed sites, with strong declines in internal variation also occurring for the transition from near‒pristine to moderately impacted landscapes. These results were consistent whether based on species‒level or genus‒level data. Variation in assemblage size structure seemed to be more predictable than taxonomic composition, supporting the notion that resemblance measurements based on body size distributions can represent an improvement to more traditional approaches based on taxonomic identities alone. In addition, we showed that macroinvertebrate assemblages resulted from effects of land‒use degradation mediated through local conditions and spurious spatial structures in the distribution of anthropogenic activities across the landscape. Overall, our findings suggest that existing water policies and agri‒environment schemes should be guided not only by understanding the individual effects of agricultural and urban development on taxonomic composition at a given stream site. Rather, we should also acknowledge the size structure of stream assemblages and whether concomitant changes in local conditions and the non‒random distribution of human infrastructures are likely to mitigate or accelerate these effects.

Biological assessment of western USA sandy bottom rivers based on modeling historical and current fish and macroinvertebrate data

Biological monitoring is important for assessing the ecological condition of surface waters. However, there are challenges in determining what constitutes reference conditions, what assemblages should be used as indicators, and how assemblage data should be converted into quantitative indicator scores. In this study, we developed and applied biological condition gradient (BCG) modeling to fish and macroinvertebrate data previously collected from large, sandy bottom southwestern USA rivers. Such rivers are particularly vulnerable to altered flow regimes resulting from dams, water withdrawals and climate change. We found that sensitive ubiquitous taxa for both fish and macroinvertebrates had been replaced by more tolerant taxa, but that the condition assessment ratings based on fish and macroinvertebrate assemblages differed. We conclude that the BCG models based on both macroinvertebrate and fish assemblage condition were useful for classifying the condition of southwestern USA sandy bottom rivers. However, our fish BCG model was slightly more sensitive than the macroinvertebrate model to anthropogenic disturbance, presumably because we had historical fish data, and because fish may be more sensitive to dams and altered flow regimes than are macroinvertebrates.

Multiple in-stream stressors degrade biological assemblages in five U.S. regions

Biological assemblages in streams are affected by a wide variety of physical and chemical stressors associated with land-use development, yet the importance of combinations of different types of stressors is not well known. From 2013 to 2017, the U.S. Geological Survey completed multi-stressor/multi-assemblage stream ecological assessments in five regions of the United States (434 streams total). Diatom, invertebrate, and fish communities were enumerated, and five types of potential stressors were quantified: habitat disturbance, excess nutrients, high flows, basic water quality, and contaminants in water and sediment. Boosted regression tree (BRT) models for each biological assemblage and region generally included variables from all five stressor types and multiple stressors types in each model was the norm. Classification and regression tree (CART) models then were used to determine thresholds for each BRT model variable above which there appeared to be adverse effects (multi-metric index (MMI) models only). In every region and assemblage there was a significant inverse relation between the MMI and the number of stressors exerting potentially adverse effects. The number of elevated instream stressors often varied substantially for a given level of land-use development and the number of elevated stressors was a better predictor of biological condition than was development. Using the adverse effects-levels that were developed based on the BRT model results, 68% of the streams had two or more stressors with potentially adverse effects and 35% had four or more. Our results indicate that relatively small increases in the number of stressors of different types can have a large effect on a stream ecosystem.

Temporal Variability of Macroinvertebrate Assemblages in a Mediterranean Coastal Stream: Implications for Bioassessment

Macroinvertebrates from a small forest stream in central-south Chile were sampled monthly from September 2017 to August 2018 to assess temporal variability in the assemblage and the effects of that variability on ecological indicators. Higher precipitation and flows occurred in winter months, and water quality varied among months. We collected 59 macroinvertebrate taxa, finding higher taxa richness and abundances in summer months than in winter months. Four taxa demonstrated marked seasonality, being abundant in some months and then decreasing in following months (Limnoperla jaffueli (Navás), Nousia maculata (Demoulin), Smicridea sp. (McLachlan), Chironomidae spp.). The scores of the family Hilsenhoff Biotic Index (HBI), Hilsenhoff Species-level Biotic Index (HSBI), Multimetric Macroinvertebrate Index (MMI), and Chilean Biological Monitoring Working Party (ChBMWP) index varied throughout the year reflecting natural variability. However, only HBI and HSBI scores were significantly different among seasons, ranging across three water quality classes (excellent, very good, and good), showing the lowest water classes in spring, coinciding with higher abundances of tolerant species. The MMI and ChBMWP indicated good and very good site conditions throughout the year, respectively. Shannon-Weaver diversity ranged between 2.59 (April) and 1.78 (February); however, Pielou evenness had high values throughout the year (> 0.62), except in February. Changes in macroinvertebrates composition throughout the year were explained primarily by discharge, water temperature, and conductivity. Our findings indicate that natural monthly variability in macroinvertebrate assemblages influences the scores of biological indices throughout the year. Therefore, we recommend that natural stream variability be accounted for in biomonitoring programs. We also emphasize the need to use caution when interpreting biological index scores to avoid misinterpretations in stream quality classification.

Comparison of benthic macroinvertebrate assessment methods along a salinity gradient in headwater streams

Benthic macroinvertebrate community assessments are used commonly to characterize aquatic systems and increasingly for identifying their impairment caused by myriad stressors. Yet sampling and enumeration methods vary, and research is needed to compare their abilities to detect macroinvertebrate community responses to specific water quality variables. A common assessment method, rapid bioassessment, uses subsampling procedures to identify a fixed number of individual organisms regardless of total sample abundance. In contrast, full-enumeration assessments typically allow for expanded community characterization resulting from higher numbers of identified organisms within a collected sample. Here, we compared these two sampling and enumeration methods and their abilities to detect benthic macroinvertebrate response to freshwater salinization, a common stressor of streams worldwide. We applied both methods in headwater streams along a salinity gradient within the coal-mining region of central Appalachia USA. Metrics of taxonomic richness, community composition, and trophic function differed between the methods, yet most metrics exhibiting significant response to SC for full-enumeration samples also did for rapid bioassessment samples. However, full-enumeration yielded taxonomic-based metrics consistently more responsive to the salinization gradient. Full-enumeration assessments may potentially provide more complete characterization of macroinvertebrate communities and their response to increased salinization, whereas the more cost-effective and widely employed rapid bioassessment method can detect community alterations along the full salinity gradient. These findings can inform decisions regarding such tradeoffs for assessments of freshwater salinization in headwater streams and highlight the need for similar research of sampling and enumeration methodology in other aquatic systems and for other stressors.

Influence of a low-head dam on water quality of an urban river system

Dam removal in the United States is becoming a common practice for stream restoration as these structures age, climate driven precipitation patterns change, and ecological uplift becomes desirable. Yet in highly urbanized watersheds, these dams may operate as retention basins removing pollutants and mitigating hydrological change. While elimination may be ecologically and economically advantageous, sediment and pollutant removal processes may be better protective of water quality and damaging flooding. In Central Virginia, we compared a watershed split between an urbanized subwatershed (>20% impervious surface encompassing 37.8% of the total watershed land surface) flowing through a 18 Ha reservoir with a rural subwatershed (<5% impervious encompassing 63.2% of the total watershed land surface) located in the James River and Chesapeake Bay watersheds. This reservoir is scheduled for removal in the near future. Comparisons of data suggest that while portions of the urbanized watershed are degraded, this condition is not reflected at the confluence where water quality more closely resembles the rural and minimally impervious subwatershed. This conclusion was further strengthened from data collected following an unexpected dam overtopping in August 2018 where the reservoir was temporarily drained because of safety concerns. After the draining, water quality reversed with the confluence resembling the urbanized rather than the rural subwatershed. Most significantly, water quality flowing into the James River quickly and significantly shifted from a good to a degraded condition. This case study suggests reservoirs in highly urbanized watersheds may serve as critical water quality improvement structures and removal as part of a stream restoration strategy must be carefully considered.

Measuring stream habitat conditions: Can remote sensing substitute for field data?

The ongoing encroachment of agricultural activities into natural areas is a growing problem for the ecological condition of streams. Stream ecological condition is best measured using both biotic and abiotic parameters that reflect different channel, riparian zone and catchment aspects. Multiple physical-chemical measures of water quality have long been widely used to represent the environmental conditions of water bodies. More recently, physical habitat structure, catchment land use and land cover have been employed to better understand water body conditions. Both water quality and physical habitat structure metrics are usually measured in the field and often have strong predictive power to analyze biological assemblage conditions. On the other hand, remote sensing of catchment land use and land cover provide relatively low-cost environmental information at large spatial extents, minimizing the need for fieldwork and reducing analytical time. Given these considerations, our aim in the present study was to evaluate the degree to which stream environmental conditions could be measured reliably via remote sensing. In particular, we assessed whether a remote sensing index (Normalized Difference Vegetation Index) and land use can be used as reliable surrogates for site habitat condition, channel dimensions, and water quality. We found that our remote sensing variables were not sufficient for predicting stream water quality or habitat structure. Therefore, we recommend using remote sensing indicators only when it is impossible to measure water quality and habitat structure in the field directly.

Agricultural Effects on Streams and Rivers: A Western USA Focus

Globally, croplands and rangelands are major land uses and they have altered lands and waters for millennia. This continues to be the case throughout the USA, despite substantial improvements in treating wastewaters from point sources—versus non-point (diffuse) sources. Poor macroinvertebrate assemblage condition occurs in 30% of conterminous USA streams and rivers; poor fish assemblage condition occurs in 26%. The risk of poor fish assemblage condition was most strongly associated with excess nutrients, salinity and sedimentation and impaired riparian woody vegetation. Although the Clean Water Act was passed to restore and maintain the integrity of USA waters, that will be impossible without controlling agricultural pollution. Likewise, the Federal Land Policy and Management Act was enacted to protect the natural condition of public lands and waters, including fish habitat, but it has failed to curtail the sacred cows of livestock grazing. Although progress has been slow and spotty, promising results have been obtained from basin and watershed planning and riparian zone protections.

Big data challenges in overcoming China's water and air pollution: relevant data and indicators

Big data are potentially useful for environmental management planning and actions that can be directed toward pollution control. China is using big data approaches to help reduce its current levels of pollution. However, also needed are better environmental indicators, measurement technologies, data management and reporting, and adaptive management and enforcement. Based on continental-extent monitoring and assessment programs in Europe and the USA, we recommend three major programmatic changes for China. (1) Establish long-term systemic environmental and human health objectives and indicators. (2) Adopt national standard methods for survey designs, sampling and analytical protocols, statistical analyses, and collaborative sampling programs. (3) Provide a transparent process for reporting and correcting data errors.

Beta diversity of aquatic macroinvertebrate assemblages associated with leaf patches in neotropical montane streams

Over 70% of the total channel length in all river basins is formed by low order streams, many of which originate on mountaintops. Headwater streams play fundamental roles in processing and transporting terrestrial and aquatic organic matter, often harboring high biodiversity in bottom leaf patches deposited from riparian vegetation. The objective of this study was to assess the variation in taxonomic composition (measured by beta diversity of aquatic macroinvertebrates) among stream sites located in the Espinhaço Meridional Mountain Range, part of a UNESCO Biosphere Reserve in eastern Brazil. We tested two hypotheses. (a) Taxa turnover is the main reason for differences in aquatic insect assemblages within stream sites; we predicted that turnover would be higher than nestedness in all stream sites. (b) Stream site altitude and catchment elevation range are the main explanatory variables for the differences in beta diversity; we predicted that local stream site variables would account for only minor amounts of variation. In both dry and wet seasons, we sampled twice in two habitat types (five leaf patches in pools and five in riffles) in each of nine stream sites distributed in three different river basins. We computed average pairwise beta diversity among sampling stations and seasons in each stream site by using Jaccard and Bray-Curtis indices, and calculated the percentages of diversity resulting from turnover and nestedness. Finally, we tested the degree that local- or catchment-level predictor variables explained beta diversity. We found that turnover was the main component of beta diversity and that both dissolved oxygen and elevation range best explained Bray-Curtis beta diversity. These results reinforce the importance of leaf patches in montane (sky islands) Neotropical savanna streams as biodiversity hotbeds for macroinvertebrates, and that both local and landscape variables explained beta diversity.

Sampling Efforts for Estimating Fish Species Richness in Western USA River Sites

Fish species richness is an indicator of river ecological condition but it is particularly difficult to estimate in large unwadeable rapidly flowing rivers. Intensive multi-gear sampling is time consuming, logistically complex and expensive. However, insufficient sampling effort underestimates species richness and yields inaccurate data about the ecological condition of river sites. We raft-electrofished 10 river sites in 10 different ecoregions and six western USA states for distances equal to 300 times their mean wetted channel widths (MCWs) to estimate the effort needed to approach asymptotes in fish species richness. To collect 90% of the observed fish species at the sites, we found that an average of 150 MCWs (ranging 80-210 MCWs) were needed, with the number of MCWs increasing in rivers with a higher proportion of spatially rare species. Frequently, the second or third additional 100 MCWs produced only one or two additional singletons or doubletons (species occurring only once or twice at a site). Before initiating sampling programs for adequately estimating species richness, we recommend assessing sampling effort, particularly if rare or uncommon species are expected or desired.

The Biological Assessment and Rehabilitation of the World's Rivers: An Overview

The biological assessment of rivers i.e., their assessment through use of aquatic assemblages, integrates the effects of multiple-stressors on these systems over time and is essential to evaluate ecosystem condition and establish recovery measures. It has been undertaken in many countries since the 1990s, but not globally. And where national or multi-national monitoring networks have gathered large amounts of data, the poor water body classifications have not necessarily resulted in the rehabilitation of rivers. Thus, here we aimed to identify major gaps in the biological assessment and rehabilitation of rivers worldwide by focusing on the best examples in Asia, Europe, Oceania, and North, Central, and South America. Our study showed that it is not possible so far to draw a world map of the ecological quality of rivers. Biological assessment of rivers and streams is only implemented officially nation-wide and regularly in the European Union, Japan, Republic of Korea, South Africa, and the USA. In Australia, Canada, China, New Zealand, and Singapore it has been implemented officially at the state/province level (in some cases using common protocols) or in major catchments or even only once at the national level to define reference conditions (Australia). In other cases, biological monitoring is driven by a specific problem, impact assessments, water licenses, or the need to rehabilitate a river or a river section (as in Brazil, South Korea, China, Canada, Japan, Australia). In some countries monitoring programs have only been explored by research teams mostly at the catchment or local level (e.g., Brazil, Mexico, Chile, China, India, Malaysia, Thailand, Vietnam) or implemented by citizen science groups (e.g., Southern Africa, Gambia, East Africa, Australia, Brazil, Canada). The existing large-extent assessments show a striking loss of biodiversity in the last 2-3 decades in Japanese and New Zealand rivers (e.g., 42% and 70% of fish species threatened or endangered, respectively). A poor condition (below Good condition) exists in 25% of South Korean rivers, half of the European water bodies, and 44% of USA rivers, while in Australia 30% of the reaches sampled were significantly impaired in 2006. Regarding river rehabilitation, the greatest implementation has occurred in North America, Australia, Northern Europe, Japan, Singapore, and the Republic of Korea. Most rehabilitation measures have been related to improving water quality and river connectivity for fish or the improvement of riparian vegetation. The limited extent of most rehabilitation measures (i.e., not considering the entire catchment) often constrains the improvement of biological condition. Yet, many rehabilitation projects also lack pre-and/or post-monitoring of ecological condition, which prevents assessing the success and shortcomings of the recovery measures. Economic constraints are the most cited limitation for implementing monitoring programs and rehabilitation actions, followed by technical limitations, limited knowledge of the fauna and flora and their life-history traits (especially in Africa, South America and Mexico), and poor awareness by decision-makers. On the other hand, citizen involvement is recognized as key to the success and sustainability of rehabilitation projects. Thus, establishing rehabilitation needs, defining clear goals, tracking progress towards achieving them, and involving local populations and stakeholders are key recommendations for rehabilitation projects (Table 1). Large-extent and long-term monitoring programs are also essential to provide a realistic overview of the condition of rivers worldwide. Soon, the use of DNA biological samples and eDNA to investigate aquatic diversity could contribute to reducing costs and thus increase monitoring efforts and a more complete assessment of biodiversity. Finally, we propose developing transcontinental teams to elaborate and improve technical guidelines for implementing biological monitoring programs and river rehabilitation and establishing common financial and technical frameworks for managing international catchments. We also recommend providing such expert teams through the United Nations Environment Program to aid the extension of biomonitoring, bioassessment, and river rehabilitation knowledge globally.

Correspondence between a recreational fishery index and ecological condition for U.S.A. streams and rivers

Sport fishing is an important recreational and economic activity, especially in Australia, Europe and North America, and the condition of sport fish populations is a key ecological indicator of water body condition for millions of anglers and the public. Despite its importance as an ecological indicator representing the status of sport fish populations, an index for measuring this ecosystem service has not been quantified by analyzing actual fish taxa, size and abundance data across the U.S.A. Therefore, we used game fish data collected from 1,561 stream and river sites located throughout the conterminous U.S.A. combined with specific fish species and size dollar weights to calculate site-specific recreational fishery index (RFI) scores. We then regressed those scores against 38 potential site-specific environmental predictor variables, as well as site-specific fish assemblage condition (multimetric index; MMI) scores based on entire fish assemblages, to determine the factors most associated with the RFI scores. We found weak correlations between RFI and MMI scores and weak to moderate correlations with environmental variables, which varied in importance with each of 9 ecoregions. We conclude that the RFI is a useful indicator of a stream ecosystem service, which should be of greater interest to the USA public and traditional fishery management agencies than are MMIs, which tend to be more useful for ecologists, environmentalists and environmental quality agencies.

Choice of field and laboratory methods affects the detection of anthropogenic disturbances using stream macroinvertebrate assemblages

Accurate and precise detection of anthropogenic impacts on stream ecosystems using macroinvertebrates as biological indicators depends on the use of appropriate field and laboratory methods. We assessed the responsiveness to anthropogenic disturbances of assemblage metrics and composition by comparing commonly employed alternative combinations of field sampling and individuals counting methods. Four datasets were derived by, in the field 1) conducting multihabitat sampling (MH) or 2) targeting samples in leaf packs (single-habitat sampling - SH) and, in the laboratory A) counting all individuals of the samples, or B) simulating subsampling of 300 individuals per sample. We collected our data from 39 headwater stream sites in a drainage basin located in the Brazilian Cerrado. We used a previously published quantitative integrated disturbance index (IDI), based on both local and catchment disturbance measurements, to characterize the intensity of anthropogenic alterations at each site. Family richness and % Ephemeroptera, Plecoptera and Trichoptera (% EPT) individuals obtained from each dataset were tested against the IDI through simple linear regressions, and the differences in assemblage composition between least- and most-disturbed sites was tested using Permutational Multivariate Analysis of Variance (PERMANOVA). When counting all individuals, differences in taxonomic richness and assemblage composition of macroinvertebrate assemblages between least- and most-disturbed sites were more pronounced in the MH than in the SH sampling method. Leaf packs seemed to concentrate high abundance and diversity of macroinvertebrates in highly disturbed sites, acting as 'biodiversity hotbeds' in these situations, which likely reduced the response of the assemblages to the disturbance gradient when this substrate was targeted. However, MH sampling produced weaker results than SH when subsampling was performed. The % EPT individuals responded better to the disturbance gradient when SH was employed, and its efficiency was not affected by the subsampling procedure. We conclude that no single method was the best in all situations, and the efficiency of a sampling protocol depends on the combination of field and laboratory methods being used. Although the total count of individuals with multihabitat sampling obtained the best results for most of the evaluated variables, the decision of which procedures to use depends on the amount of time and resources available, on the variables of interest, on the availability of habitat types in the sites sampled, and on the other methods being employed in the sampling protocol.