Article

The Biological Condition Gradient: A Descriptive Model for Interpreting Change in Aquatic Ecosystems

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Abstract

The United States Clean Water Act (CWA; 1972, and as amended, U.S. Code title 33, sections 1251-1387) provides the long-term, national objective to "restore and maintain the ... biological integrity of the Nation's waters" (section 1251). However, the Act does not define the ecological components, or attributes, that constitute biological integrity nor does it recommend scientific methods to measure the condition of aquatic biota. One way to define biological integrity was described over 25 years ago as a balanced, integrated, adaptive system. Since then a variety of different methods and indices have been designed and applied by each state to quantify the biological condition of their waters. Because states in the United States use different methods to determine biological condition, it is currently difficult to determine if conditions vary across states or to combine state assessments to develop regional or national assessments. A nationally applicable model that allows biological condition to be interpreted independently of assessment methods will greatly assist the efforts of environmental practitioners in the United States to (1) assess aquatic resources more uniformly and directly and (2) communicate more clearly to the public both the current status of aquatic resources and their potential for restoration. To address this need, we propose a descriptive model, the Biological Condition Gradient (BCG) that describes how 10 ecological attributes change in response to increasing levels of stressors. We divide this gradient of biological condition into six tiers useful to water quality scientists and managers. The model was tested by determining how consistently a regionally diverse group of biologists assigned samples of macroinvertebrates or fish to the six tiers. Thirty-three macroinvertebrate biologists concurred in 81% of their 54 assignments. Eleven fish biologists concurred in 74% of their 58 assignments. These results support our contention that the BCG represents aspects of biological condition common to existing assessment methods. We believe the model is consistent with ecological theory and will provide a means to make more consistent, ecologically relevant interpretations of the response of aquatic biota to stressors and to better communicate this information to the public.

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... Scientific tools and approaches, like the ESG, can help to operationalize EBM in the decision-making process by identifying meaningful measures, defining reference points, communicating and monitoring the relevant social and economic impacts of actions, and evaluating tradeoffs across multi-sector objectives ). The conceptual foundation for an ESG follows that of the Biological Condition Gradient (BCG), developed over a decade ago in response to growing need to assess and effectively communicate levels of biological condition in a meaningful way (Davies and Jackson 2006;U.S. EPA 2016). The BCG leverages expert knowledge and biomonitoring data to describe ecological condition along a gradient from undisturbed to severely altered conditions. ...
... The BCG is a descriptive model that describes how attributes of biological condition change in response to increasing levels of anthropogenic stress ( Fig. 1a; Davies and Jackson 2006). The BCG approach was developed to address a need for sciencebased approaches to more precisely and effectively communicate the existing and potential condition of aquatic resources for water quality management purposes under the U.S. Clean Water Act (United States Code title 33, sections 1251-1387). ...
... In environmental management situations where protecting biological integrity is the primary goal, directly pairing an ESG with a BCG can help decision-makers understand the potential co-occurring benefits and tradeoffs of management activities and communicate them to the public (Fig. 1). Furthermore, if a waterbody is designated for a particular use, such as recreational fisheries or contact recreation, an assessment of ecosystem services in conjunction with BCG can help identify the levels of biological condition that can be protected while still supporting desired levels of services (Davies and Jackson 2006). Adapted from Cicchetti et al. 2017 An additional step (in italics) indicates where an assessment of ecosystem services could supplement the process, and in conjunction with stressor and other data, inform management decisions Along a gradient of declining biological condition, ecosystem services may decline at different rates depending on the biological attributes providing those services (Fig. 1b). ...
... Biological integrity has been defined as "the capability of supporting and maintaining a balanced, integrated, adaptive community of organisms having a composition and diversity comparable to that of the natural habitats of the region" (Frey 1977), but the term is not specifically defined in the CWA itself. Nor does the CWA define the ecological components, or attributes, that constitute biological integrity (Davies and Jackson 2006). ...
... Given this lack of specificity, a way to interpret biological condition consistently and independently of assessment methods would more clearly communicate the current status of aquatic resources and their potential for restoration (Davies and Jackson 2006), allowing scientists and managers to better assess aquatic resources. These gaps in the available management tools led the U.S. EPA Office of Water Biocriteria Program to develop the concept of a BCG. ...
... In general, measures of biological structure, non-native taxa, and condition (described above) are more available than measures of biological function and connectance as described below (Davies and Jackson 2006). Yet, these higher attributes may better address concepts of sustainability and resilience, and may help identify and predict critical ecosystem shifts and tipping points such as system-level anoxia or coral reef loss. ...
Technical Report
Full-text available
The Biological Condition Gradient (BCG) allows bioassessment data to be translated into multiple levels that provide a common scale to allow comparison of condition. Another key component of this approach is that these levels are anchored by a common baseline (as naturally occurred). This report provides guidance for application of BCG and BCG components to estuaries and coasts while providing a guide to apply BCG to other complex ecosystems. It includes guidance for incorporating data from multiple habitats and indicators to better manage aquatic resources.
... One biomonitoring framework that can be simplified and used for the assessment of ecological conditions is the United States Environmental Protection Agency's Biological Condition Gradient (BCG; Davies and Jackson, 2006;USEPA, 2016). The BCG is grounded on the concepts of stress ecology articulated by Odum et al. (1979), Odum (1985), Rapport et al. (1985), and Cairns et al. (1993). ...
... Along this disturbance gradient, assemblages of taxa are selected and used to describe ecological conditions for the sites. The original BCG was developed based on common patterns of biological response to stressors observed empirically by aquatic biologists and ecologists from different geographic areas in the United States (Courtemanch et al., 1989;Courtemanch, 1995;Yoder and Rankin, 1995;Davies and Jackson, 2006). Using the practical experience of a diverse group of aquatic scientists from different biogeographic areas and independent of specific methods of assessment, the BCG is a heuristic model based on generalized observable changes in the aquatic community that can be used as a common language expressing habitat condition and change (Davies and Jackson, 2006;USEPA, 2016). ...
... The original BCG was developed based on common patterns of biological response to stressors observed empirically by aquatic biologists and ecologists from different geographic areas in the United States (Courtemanch et al., 1989;Courtemanch, 1995;Yoder and Rankin, 1995;Davies and Jackson, 2006). Using the practical experience of a diverse group of aquatic scientists from different biogeographic areas and independent of specific methods of assessment, the BCG is a heuristic model based on generalized observable changes in the aquatic community that can be used as a common language expressing habitat condition and change (Davies and Jackson, 2006;USEPA, 2016). The USEPA has extended the use of the BCG concept to other aquatic habitats including coral reefs, estuaries, and mangroves. ...
Article
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The biological condition gradient (BCG), a scientific framework that describes the change in ecosystem characteristics in response to human-induced levels of stressors, was modified and used to characterize watershed habitats in the Upper Tana River watershed, Kenya. The inbuilt utilities of BCG, including its simplicity, versatility, and its robust nature, allowed its use by seven taxonomic groups of macroinvertebrates, diatoms, fish, herpetofauna (amphibians and reptiles), plants, macrofungi, and birds to assess and monitor landscape conditions in both terrestrial and aquatic habitats. The biological data were described using taxa abundance distribution measures followed by multivariate analyses to determine their relationship with water or soil quality and thereafter assessment of taxa tolerant levels in response to environmental stress and disturbances. Preliminary findings reported that the taxonomic groups complemented each other, with each taxonomic group reliably assessing ecological conditions to a certain degree that supported assigning all 36 sampled sites into BCG tiers. The BCG models developed for all taxonomic groups assisted in the identification and selection of taxa indicating varying levels of landscape conditions. These taxa, referred to as flagship or indicator taxa, assist in simplifying the BCG model and, hence, are possible for use by parataxonomists or ordinary citizens to assess and monitor the ecological health of habitats under consideration. Furthermore, the capability of BCG models to assess landscape conditions shows how they can be used to identify important habitats for conservation, direct investment for restoration, and track progress.
... Briefly, this is accomplished by using the residuals from regression lines as the response variables; however, such indices only assess the observed occurrences of non-rare taxa versus their expected occurrences. Rare, often sensitive, taxa are omitted from such analyses and those taxa are often the first to disappear during the early stages of anthropogenic disturbances (Davies & Jackson, 2006;Leitão et al., 2016;R. T. Martins et al., 2021). ...
... T. Martins et al., 2021). Also, some tolerant taxa are more likely to occur in the early stages of anthropogenic disturbance, thereby, resulting in no change or even an increase in taxa richness (Davies & Jackson, 2006;R. T. Martins et al., 2021). ...
... This approach has been applied at national and ecoregional (Herlihy et al., 2020;USEPA, 2016a), as well as basin I. Martins et al., 2020;Mulvey et al., 2009;Silva et al., 2017) spatial extents. An alternative approach, employing many of the same metrics used in MMIs, but with a differing concept for reference conditions and assemblage scoring, is the biological condition gradient (BCG) assessment (Davies & Jackson, 2006;USEPA, 2016c). ...
Article
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.
... The Biological Condition Gradient (BCG) is a conceptual model that relates biological condition to increasing levels of anthropogenic stress and can be used to identify biological attributes and measurable increments of change from biological condition assessments (Davies and Jackson 2006;US EPA, 2016). The BCG describes six biological condition levels ranging from undisturbed or natural (BCG level 1) to highly disturbed or degraded conditions (BCG level 6) ( Fig. 1). ...
... As demonstrated in the present study and noted elsewhere (Jackson et al. 2014, Pandolfi et al. 2003, Pandolfi et al., 2005, undisturbed or natural reefs have largely disappeared from the Caribbean, impressing the urgency for tools such as BCG models to assist natural resource managers and stakeholders evaluate changes in coral reefs. This framework was originally implemented in freshwater systems in the USA to support state biological assessment and criteria programs (Davies and Jackson 2006). Santavy et al. (2016) proposed an adaptation of the BCG framework to apply to reef corals in the Caribbean as a proof of concept. ...
... Ten BCG attributes are generally defined in the BCG framework for all environments, and they incorporate taxa sensitivity, organism condition, and ecosystem functions (Davies and Jackson 2006; US EPA, 2016) ( Table 2). Attributes are responsive to taxa structure and compositional changes when exposed to major anthropogenic stressors. ...
Article
As coral reef condition and sustainability continue to decline worldwide, losses of critical habitat and their ecosystem services have generated an urgency to understand and communicate reef response to management actions, environmental contamination, and natural disasters. Increasingly, coral reef protection and restoration programs emphasize the need for robust assessment tools for protecting high-quality waters and establishing conservation goals. Of equal importance is the need to communicate assessment results to stakeholders, beneficiaries, and the public so that environmental consequences of decisions are understood. The Biological Condition (BCG) model provides a structure to evaluate the condition of a coral reef in increments of change along a gradient of human disturbance. Communication of incremental change, regardless of direction, is important for decision makers and the public to better understand what is gained or lost depending on what actions are taken. We developed a narrative (qualitative) Biological Condition Gradient (BCG) from the consensus of a diverse expert panel to provide a framework for coral reefs in US Caribbean Territories. The model uses narrative descriptions of biological attributes for benthic organisms to evaluate reefs relative to undisturbed or minimally disturbed conditions. Using expert elicitation, narrative decision rules were proposed and deliberated to discriminate among six levels of change along a gradient of increasing anthropogenic stress. Narrative rules for each of the BCG levels are presented to facilitate the evaluation of benthic communities in coral reefs and provide specific narrative features to detect changes in coral reef condition and biological integrity. The BCG model can be used in the absence of numeric, or quantitative metrics, to evaluate actions that may encroach on coral reef ecosystems, manage endangered species habitat, and develop and implement management plans for marine protected areas, watersheds, and coastal zones. The narrative BCG model is a defensible model and communication tool that translates scientific results so the nontechnical person can understand and support both regulatory and non-regulatory water quality and natural resource programs.
... Pollution tolerant and sensitive diatom assemblages accurately indicate the variation in environmental conditions under human disturbance with a loss of sensitive species or an increment of tolerant species (Davies and Jackson, 2006). Strong relationships between diatoms and stressors (e.g., nutrients especially soluble reactive phosphorus and TP electrical conductivity, salinity, acidity, etc.) are quantifiable in the different trophic gradients from reference sites to highly disturbed sites. ...
... The BCG was developed in the United States to standardize bioassessment in freshwater bodies with CWA's objectives. The BCG, a scientific characterization of the biological response to increasing effects of stressors, is an ecosystembased framework that independently evaluates chemical, physical, and biological conditions (Davies and Jackson, 2006). ...
... Ecological features reflecting the degree to which a system is moving away from its natural structure are expressed in the concept of biological status (Davies and Jackson, 2006;Hausmann et al., 2016;Charles et al., 2019;Ruaro et al., 2020). Six levels in the BCG have been briefly defined as level 1-natural or very little affected condition, level 2-minimal changes in biotic structure and ecosystem function, level 3-minimal changes in ecosystem Table 2. function and significant changes in biotic community structure, level 4-moderate changes in biotic structure, minimal changes in ecosystem function, level 5-major changes in biotic community structure, moderate changes in ecosystem function, and level 6-biotic community dramatically changed, a great loss of ecosystem (Davies and Jackson, 2006;Hausmann et al., 2016). ...
Article
Full-text available
Bioassessment of surface waters is one of the most important approaches to predict the deterioration of ecosystems and achieve environmental sustainability according to the application of the European Water Framework Directive. The present review emphasizes the importance of the bioassessment of freshwater quality especially running waters based on diatom metrics. Nutrient enrichment and hydromorphological alternation driven by human activities are the main factors for the ecological compromise of freshwater ecosystems. Currently, the bioassessment of the ecological condition of inland water bodies is adopted worldwide. Bioassessment is complementary to physico-chemical and hydromorphological data for evaluating the ecological conditions of rivers; however, measuring all the physical and chemical changes is expensive and impractical. Therefore, monitoring biota helps to determine the changes occurring in ecosystems. Thus, diatoms are used as bioindicators to assess environmental conditions of the ecosystems, but their use requires great taxonomic knowledge, otherwise, the results will be biased. Many diatom indices have been developed based on the trophic weight and indicator values of diatoms in different ecoregions in the last decades. This review highlights the importance and advantages of using diatom metrics in the bioassessment of the ecological status of surface waters in the different ecoregions, especially running water. To analyze the complex response of diatom communities to environmental gradients and assess the quality of the ecosystem, multivariate statistical approaches are needed. The challenge here is how to define criteria for classes of water bodies in a biologically meaningful way. For this reason, Biological Condition Gradient is suggested as an appropriate and effective approach to develop trophic criteria based on the relationships between nutrient concentrations and biological indicators of ecological conditions.
... MMIs also behave like species-rich fish assemblages and life-history rich fish populations that respectively limit assemblage and species variability (Karr et al., 1986;Schindler et al., 2010). Therefore, Karr (1981), Davies and Jackson (2006) and Hughes and Noss (1992) argued that biological condition is best assessed by evaluating multiple structural and functional metrics. ...
... (5) A relatively low score for one metric might lower the overall MMI score slightly, but it will not overwhelm the total MMI score. For example, an otherwise high-quality stream may be dominated by invasive non-native trout species and would, therefore not be considered as being in as good an ecological condition as a stream supporting only native fish species (Davies and Jackson, 2006;Hughes et al., 2004;Lomnicky et al., 2021;Mebane et al., 2003). (6) Major reasons for poor MMI scores are known. ...
... Failing to make them so will lead to biased measurements of deviation (Feio et al., 2014;Hawkins et al., 2010). In addition, Davies and Jackson (2006) emphasized characterizing reference condition quality by using a biological condition gradient (BCG). The BCG provides a step toward a standardized scale for assessing biological condition. ...
Article
Full-text available
Freshwater biota are more comprehensive and direct indicators of biological impacts, and more meaningful to the public than water quality or physical habitat surrogates. Freshwater biotic data and the multiple biological indicators developed from them offer a much richer array of data for assessing the impacts of pollution controls than a limited set of physical or chemical measures. In recent decades, assemblage-based assessments by ecologists, environmental scientists, and water quality agencies have been employed globally for determining the condition of, and threats to, freshwater ecosystems. A key step in this advance has been the development of multimetric indices (MMIs) or indices of biotic integrity (IBIs) based on quantitative assessments of algae, macrophyte, macroinvertebrate, fish or riparian bird assemblages. In Europe, where biological assemblages are mandated for assessing freshwater ecosystem health, many indices are multimetric. However, the proliferation of MMIs globally has not always occurred through the application of rigorous study designs and monitoring protocols, nor have they always effectively incorporated functional metrics, stressor assessments, and statistical analyses. Therefore, in this review, we discuss eleven major concerns with the development and application (including logistical limitations) of multimetric indicators based on freshwater biota to encourage more rigorous and widely applicable (transferable) MMI use and implementation. Specifically, our concerns focus on reference conditions; sampling effort, methods, and season; trophic guild definition; metric comprehensiveness, options, screening and scoring; and MMI validation. MMIs could also benefit from increased attention to ecological mechanisms and metric development, to further improve our understanding of anthropogenic impacts as well as rehabilitation effects on freshwater ecosystems globally. Paying closer attention to study designs, ecological mechanisms and metric development should further improve our understanding of anthropogenic impacts and better facilitate rehabilitation of degraded freshwater ecosystems, as well as aiding in the conservation of healthy freshwater ecosystems globally.
... Biological integrity has been defined as "the capability of supporting and maintaining a balanced, integrated, adaptive community of organisms having a composition and diversity comparable to that of the natural habitats of the region" (Frey 1977), but the term is not specifically defined in the CWA itself. Nor does the CWA define the ecological components, or attributes, that constitute biological integrity (Davies and Jackson 2006). ...
... Given this lack of specificity, a way to interpret biological condition consistently and independently of assessment methods would more clearly communicate the current status of aquatic resources and their potential for restoration (Davies and Jackson 2006), allowing scientists and managers to better assess aquatic resources. These gaps in the available management tools led the U.S. EPA Office of Water Biocriteria Program to develop the concept of a BCG. ...
... In general, measures of biological structure, non-native taxa, and condition (described above) are more available than measures of biological function and connectance as described below (Davies and Jackson 2006). Yet, these higher attributes may better address concepts of sustainability and resilience, and may help identify and predict critical ecosystem shifts and tipping points such as system-level anoxia or coral reef loss. ...
Technical Report
Full-text available
Technical Report by the US EPA describes the Biological Condition Gradient (BCG) approach and utilizes data within an estuarine ecosystem gradient to assist in projecting realistic environmental ecosystem restoration goals
... Biological Condition Gradient (BCG) models for fish assemblages in Minnesota lakes were developed independently of the FIBIs to define changes to the fish communities along a gradient of increasing anthropogenic stress. The BCG is a conceptual model that describes changes in aquatic communities along a gradient in response to increasing levels of human disturbance and is useful in establishing ecologically meaningful thresholds (Davies and Jackson, 2006). The BCG models in this study used rules to classify lakes into six levels along a degradation gradient with level one describing lakes where system functionality is intact and all natural biological components are retained. ...
... Lakes with FIBI scores near the General Use impairment threshold generally contained a lower diversity and proportion of intolerant species, a higher proportion of biomass from tolerant species, and a higher proportion of biomass from omnivores relative to insectivores. These observations were consistent with the description provided by Davies and Jackson (2006), where BCG level 4 corresponds with moderate changes in the structure of the biotic community due to replacement of some sensitive taxa by more tolerant taxa. The Exceptional Use threshold was assigned for lake groups 2 and 4 at scores corresponding to the upper quartile of BCG level 3, which was very similar in value to the median of BCG level 2 (Fig. 12). ...
... Likewise, insectivores, top carnivores, and vegetation-dwelling species represented a large proportion of the catch in these lakes. These observations were also in alignment with the descriptions of BCG levels 2 and 3, where either virtually all native taxa are maintained or where some changes in biotic community structure have occurred due to loss of some rare native taxa but where sensitive taxa are still common and abundant (Davies and Jackson, 2006). Impairment thresholds varied from 24 to 45 (Fig. 12). ...
Article
Full-text available
Indices of biological integrity (IBIs) have been developed for a wide variety of locales and ecological systems to describe their biological condition. Due to variability in geophysical and chemical conditions, IBIs are often developed regionally and applied to similar ecological systems. Researchers in Minnesota previously developed a fish IBI (FIBI) for lakes; however, its application was limited to lakes 40–200 ha surface area and located in central Minnesota. The objectives of this study were to develop FIBIs and ecologically meaningful thresholds for application to a broader suite of Minnesota lakes with surface areas 40–4,050 ha. Fish communities in 419 lakes throughout Minnesota were sampled using gill nets, trap nets, backpack electrofishers, and beach seines between mid-June and early-September 2005–2013. Fish species were assigned to functional groups based on family, tolerance, primary feeding niche, special habitat use, and whether they were native to Minnesota. Lakes were classified into seven groups based on their geophysical and chemical attributes, and four groups were ultimately used in FIBI development. A suite of potential metrics was evaluated for each of the four FIBIs based on their relationships to measures of human-induced watershed and in-lake stressors and 8–15 were retained for each FIBI. Metrics that were retained were summed, and composite scores were scaled 0–100. Biological Condition Gradient (BCG) models were developed for each FIBI. The BCG models established thresholds for impairment and exceptional condition. The FIBIs and thresholds are being used to guide clean water planning, restoration, and protection efforts and to complement pollutant-based water quality sampling efforts in lakes during the Minnesota watershed assessment process.
... Proving information on the extent of lakes and streams that support healthy biological condition is one important purpose of National Lake Assessment (NLA) project and National Rivers and Streams Assessment (NRSA) project of the US Environmental Protection Agency (USEPA). Assessment of biological condition of freshwater ecosystems is better than chemistry and physical habitat structure assessment because it can integrate multiple long-term anthropogenic stressors (Karr and Dudley, 1981;Davies and Jackson, 2006) and is less affected by natural variability and effort put in sampling (Hughes, 2019). Structure and functional measures of fish (Santos and Esteves, 2015;Gonino et al., 2020), macroinvertebrates (Lau and Lauer, 2015;Silva et al., 2018;Shull et al., 2019), plants (Feio et al., 2012;Noordhuis et al., 2015;Moges et al., 2016), and algae (Cao et al., 2007;Fetscher et al., 2014;Liu et al., 2020a) are commonly used in ecological condition assessment of freshwater ecosystems. ...
... MMI result consistency, reproducibility and interpretability are valuable for large scale assessments and communicate more clearly to the public of the biological condition of freshwater ecosystems (Davies and Jackson, 2006;Cao and Hawkins, 2011). Previously, development and application of MMI method was criticized for problems such as method on metric selection (Suter, 1993). ...
... separation power). However, the consistency of an assessment is undermined at the same time (Davies and Jackson, 2006). So far, for national scale assessments in the US, varying metrics worked well on improve performance of assessment when used together with site specific metric modeling in streams and rivers (Tang et al., 2016) but not in lakes (Table 2, Liu and Stevenson, 2017). ...
Article
Multimetric index (MMI) approach is a broadly used in ecological assessment because it can integrate information of various kinds of ecologically related metrics of freshwater ecosystems and provide an easily understandable score for purpose of further evaluation and managements. Accounting for natural variation and disentangling covariation between natural environmental factors and human disturbance factors are imperative for an accurate assessment. Lots of progress has been made recently on the aforementioned two aspects. Three approaches, a priori classification of sites by regions or typologies, site-specific modeling of expected reference condition and varying metrics in site groups, have been tested in lakes and streams to improve assessment accuracy. All existed studies support that site-specific modeling can efficiently account for natural variation and generate a MMI with good performance. However, until now, no strong evidence has shown that diatom/blue-algae typologies are better than regionalization frameworks on accounting for natural variation either in lakes or in streams. To separate the natural variation explained by site specific modeling from that of varying metrics is necessary for a thorough and accurate evaluation on the valuableness of site-grouping by typologies. Different performance of varying metrics among site groups of streams and lakes was most probably caused by the lack of representativeness of diatom metrics on biological condition rather than the complex multi-stressor gradients in streams and rivers. A recent study showed that blue-green algae enhanced performance of diatom-based MMI on defining lake condition under high level of human disturbance. On the other hand, with more and more extensive and intensive use of statistics techniques in developing MMI, we also discussed some statistical challenges faced by scientists in field of ecological assessment, especially on setting significance level of a statistical test and multiple comparison issue in MMI performance comparation.
... Scientists may use reintroduction as a research tool to test hypotheses about limits to recovery, identify linkages between species and stressors (Davies andJackson 2006, Paul et al. 2009), understand species' tolerances, and create metapopulations (Patrick et al. 2021). The study's goals will help determine what information is needed pre-and postreintroduction to evaluate reintroduction success (Table 1) and develop shared expectations among stakeholders. ...
... Defining success Before reintroduction projects begin, it is important to consider how success will be defined and assessed. Definitions of ecological success vary (Table 1) and depend on project goals (see What are the goals of reintroduction?) and the stream's potential to support a more diverse assemblage of macroinvertebrates (Davies andJackson 2006, Paul et al. 2009). ...
... Ecological monitoring activities for many state and federal agencies are implemented with the goal of characterizing changes in the biological condition of an ecosystem (Barbour et al., 1999;Stoddard et al., 2006). These quantitative assessments are typically grounded on empirical data collected from numerous "reference" or "least disturbed" sites to construct regionally calibrated biological indices that typically employ a space-for-time study design across a gradient of environmental conditions (Davies and Jackson, 2006). By combining multiple, instream physicochemical predictors with associated landscape changes, these assessments can help identify the important drivers of biological stream condition and determine if stream health is degraded compared to "reference" conditions (Davies and Jackson, 2006). ...
... These quantitative assessments are typically grounded on empirical data collected from numerous "reference" or "least disturbed" sites to construct regionally calibrated biological indices that typically employ a space-for-time study design across a gradient of environmental conditions (Davies and Jackson, 2006). By combining multiple, instream physicochemical predictors with associated landscape changes, these assessments can help identify the important drivers of biological stream condition and determine if stream health is degraded compared to "reference" conditions (Davies and Jackson, 2006). But biological condition may change over time, if environmental degradation or restoration efforts progress, so repeated sampling at the same site across a range of environmental conditions could facilitate a clearer understanding of how modifications in landscape, climate, and instream predictors can influence biological stream condition. ...
Article
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Stream ecosystems are complex networks of interacting terrestrial and aquatic drivers. To untangle these ecological networks, efforts evaluating the direct and indirect effects of landscape, climate, and instream predictors on biological condition through time are needed. We used structural equation modeling and leveraged a stream survey program to identify and compare important predictors driving condition of benthic macroinvertebrate and fish assemblages. We used data resampled 14 years apart at 252 locations across Maryland, USA. Sample locations covered a wide range of conditions that varied spatiotemporally. Overall, the relationship directions were consistent between sample periods, but their relative strength varied temporally. For benthic macroinvertebrates, we found that the total effect of natural landscape (e.g., elevation, longitude, latitude, geology) and land use (i.e., forest, development, agriculture) predictors was 1.4 and 1.5 times greater in the late 2010s compared to the 2000s. Moreover, the total effect of water quality (e.g., total nitrogen and conductivity) and habitat (e.g., embeddedness, riffle quality) was 1.2 and 4.8 times lower in the 2010s, respectively. For fish assemblage condition, the total effect of land use-land cover predictors was 2.3 times greater in the 2010s compared to the 2000s, while the total effect of local habitat was 1.4 times lower in the 2010s, respectively. As expected, we found biological assemblages in catchments with more agriculture and urban development were generally comprised of tolerant, generalist species, while assemblages in catchments with greater forest cover had more-specialized, less-tolerant species (e.g., Ephemeroptera, Plecoptera, and Trichoptera taxa, clingers, benthic and lithophilic spawning fishes). Changes in the relative importance of landscape and land-use predictors suggest other correlated, yet unmeasured, proximal factors became more important over time. By untangling these ecological networks, stakeholders can gain a better understanding of the spatiotemporal relationships driving biological condition to implement management practices aimed at improving stream condition.
... Models of the response of aquatic ecosystems to stress have been proposed. For example, the Biological Condition Gradient is a conceptual model that describes structural and functional changes in streams in response to increasing levels of stressors (Davies and Jackson 2006). This model has been applied to a variety of situations (Davies and Jackson 2006, Gerritsen et al. 2017, Paul et al. 2020, including some cases of AMD (Smucker et al. 2014 and references therein). ...
... For example, the Biological Condition Gradient is a conceptual model that describes structural and functional changes in streams in response to increasing levels of stressors (Davies and Jackson 2006). This model has been applied to a variety of situations (Davies and Jackson 2006, Gerritsen et al. 2017, Paul et al. 2020, including some cases of AMD (Smucker et al. 2014 and references therein). Niyogi et al. (2002) proposed that stress on a system (even at low levels) reduces biodiversity but does not change the biomass or the functions unless the stress is intense. ...
Article
This study investigated seasonal changes in the longitudinal pH gradient of a naturally acidified river and how the attributes of epilithic algae (biomass, abundance, diversity) react to these variations. Five sites were selected on the Río Agrio river for in situ measurements, water sampling, and epilithic algae collection in different seasons from 2007 to 2018. Water pH increased along the length of the river, the average increase being highest in summer (from 2.5 to 7.0, acidity to neutrality) and lowest in spring (from 2.8 to 4.0, acidity to acidity). Conductivity and nutrient and ion concentrations decreased along the length of the river, showing a seasonal pattern of variation mainly influenced by the hydrological cycle. Epilithic algal biomass varied seasonally along the river, generally increasing in summer and decreasing in spring, with seasonal maximum values at different locations mainly associated with the dynamics of iron precipitation and nutrient availability. Species diversity and numbers were low at the most acidic site (regardless of season), but in the remaining sites these attributes tended to increase during summer–autumn and decrease during winter–spring. Statistical analysis showed that differences between sites responded mainly to the chemical gradient of the river and seasonality. Therefore, seasonal changes in the longitudinal chemical gradient of the river imposed differential, changing conditions on the epilithic algae present in each site, allowing identification of characteristic zones and their respective epilithic algal attributes. In the context of proposed models of ecosystem response to stress, similarities with systems acidified by anthropic activities are discussed.
... ecosystem state (Table 2) are based on Xu et al. (2001), Odum (2014), Odum (1985), Qi et al. (2018a), Qi et al. (2018b), and Davies and Jackson (2006). TCA index calculation ways are shown in Table S2. ...
Article
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Assessing ecosystem states quantitatively or qualitatively is important for ecosystem management. Currently, Traditional Comprehensive Assessment (TCA), including ecosystem health, risk, and service assessment is used most often. Ecosystem stability theory (EST) and ecosystem regime shift theory (RST) from mathematical ecology have not been widely used. In this paper, we compare TCA and EST and RST result using two lakes, Onondaga Lake and Poyang Lake, as case studies. We find that biological oxygen demand (BOD) could be a suitable variable to calculate temporal stability and variance indexes in EST and RST, and trend in general. The result could replace TCA when the key lake driver is not too extreme. This recommendation is preliminary, needing validated with data.
... The regression and disturbance threshold method I applied is very similar to the theoretical methodology in Rocchio & Crawford (2013). Rocchio & Crawford (2013) present a hypothetical regression relationship between a continuous measure of human disturbance and MeanCC (adapted from Davies & Jackson 2006) and indicate how reference values in MeanCC could be determined through use of thresholds in human disturbance score. ...
Thesis
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Floristic Quality Assessment (FQA) is used to describe the quality of natural areas based on plant species composition. Despite widespread application of FQA in the USA, less research exists in Ontario. To better understand FQA's monitoring, reporting, and management relevance to southern Ontario I investigated: (1) performance of FQA against a composite disturbance gradient; and, (2) differences in FQA between different vegetation communities and successional stages. My work utilized monitoring data from 422 Vegetation Sampling Protocol plots sampled throughout Lake Simcoe watershed. FQA indices were found to significantly decrease in response to increasing disturbance, outperforming native species richness and percent exotic species as indicators of disturbance. Values of FQA indices differed among vegetation communities and successional stages, indicating comparisons should not be made across natural area classes. I demonstrate FQA as an effective tool for assessing natural cover quality; however, appropriate interpretation and management application require understanding FQA's properties. https://tspace.library.utoronto.ca/handle/1807/101352
... The ecosystem assessment framework is given in Table 2. The relevant relationships between the direction of change for each index and the ecosystem state are established based on certain literature [11] [14] [24] [25], where a positive sign represents an increase in the index value and a negative sign represents a decrease, and each index is associated with movement toward a 'better state'. Because the seasonal cycle of the water volume time series is approximately 4 years, in the first case study, the mean value of the variable is calculated as a 4-year moving average. ...
Article
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Energy engineering, such as hydroelectric stations, greatly affects the environment. Under the effect of the Three Gorges Dam, the water level of Poyang Lake has decreased. The dry season of Poyang Lake has become longer, leading to many consequences. The government proposed that a sluice be built in Poyang Lake to regulate the water level. We established AQUATOX model of Poyang Lake with different water flow in and out to simulate the ecosystem with changing water volume (water level). The data used in this paper are the output of the AQUATOX model. This paper proposes and uses a framework for ecosystem assessment of the body of Poyang Lake. The results show that the ecosystem quality of the body of Poyang Lake will become increasingly worse if no action is taken. If the necessary connectivity (for migratory creatures) is ensured, building a sluice can improve the ecosystem quality of the body of Poyang Lake. We also discusses the possibility of using ecosystem stability and regime shift indexes in ecosystem assessments.
... The statistical pressure-response relationship between phosphorus and eutrophication (as expressed by phytoplankton metrics) has been often recorded as stronger than that for nitrogen [8] and thus, it is not surprising that the majority of European MSs have already established boundary for P values [33]. Model approaches developed more than 20 years ago [34,35] simulating BQEs responses to a given environmental gradient reflecting ecological condition set the basis for the contemporary WFD ecological quality classification. Different BQEs can act as pressure-respondents with complementary roles as proxies of structural and functional ecology [36]. ...
Article
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Eutrophication caused by nutrient enrichment is a predominant stressor leading to lake degradation and, thus, the set-up of boundaries that support good ecological status, the Water Framework Directive’s main target, is a necessity. Greece is one of the Member States that have recorded delays in complying with the coherent management goals of European legislation. A wide range of different statistical approaches has been proposed in the Best Practice Guide for determining appropriate nutrient thresholds. To determine the nutrient thresholds supporting the good status of natural Greek lakes, the phytoplankton dataset gathered from the national monitoring programme (2015–2020) was used for shallow and deep natural lakes. The regression analyses were sufficient and robust in order to derive total phosphorus thresholds that ranged from 20 to 41 μg/L in shallow and 15–32 μg/L in deep natural lake types. Nutrient boundaries that encompass the stressors these lakes are subject to, are essential in proper lake management design.
... To better assess the sensitivities of aquatic biota, it is useful to examine their threshold responses to anthropogenic stressors and pressures, instead of assuming linear responses (With and King, 1999;Davies and Jackson, 2006;Baker and King, 2010;King and Baker, 2010). Although the vast majority of threshold studies have focused on a single assemblage, it is important to assess threshold responses of different groups of organisms (e.g., fish and macroinvertebrates) because they play different roles in ecosystems and have differing sensitivities to stressors and pressures (Chen et al., 2017). ...
Article
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Deforestation is a major threat globally, but especially in tropical regions because they are biodiversity strongholds and carbon storehouses. Some studies have reported changes in species richness and composition in lotic ecosystems with increased forest-loss in their catchment, presumably resulting from the replacement of sensitive taxa by more resistant or tolerant taxa. Also, sensitive taxa respond to deforestation in a non-linear manner and fish and macroinvertebrates have different sensitivities to landscape pressures. Therefore, it is useful to determine the effects of forest-loss on widespread sensitive or threshold taxa in aquatic ecosystems. We used Threshold Indicator Taxa Analysis (TITAN) to assess forest-loss and land use history impacts in 92 eastern Amazonian stream sites. We determined TITAN peak-change thresholds for fish at 1% and 6% of forest-loss at total-catchment and local-riparian spatial extents, respectively, and at 2% and 40% of land-use intensity change at total-catchment and local-riparian spatial extents, respectively. For macroinvertebrates, TITAN peak-change thresholds were 1% and 11% of forest loss at total-catchment and local-riparian spatial extents, respectively, and at 3% of land-use intensity change for both total-catchment and local-riparian spatial extents. Because of these thresholds, inherent ecoregional variability and key literature, we have three major recommendations. 1) Logging should be prohibited in riparian reserves that are at least 100-m wide on each side of headwater streams and in a network of catchments across all biomes and as many landscape types as possible. 2) An ecologically and statistically rigorous monitoring program with standard methods should be implemented to assess and regulate land uses better. 3) Conservation planning areas should consider aquatic biota as well as terrestrial biota.
... They pre-date some of the rapidly changing uses of land and environmental conditions, and do not capture the state of current fish communities and overall ecosystem health status (Masese and McClain, 2012;Masese et al., 2020a). To develop fish indices that will reliably assess the health of riverine ecosystems in the LVB, it is necessary to consider fish communities that reflect the period of disturbance, as disturbance gradients are associated with losses of sensitive or intolerant species and increases in tolerant species (Vázquez and Simberloff, 2002;Davies and Jackson, 2006). As a result, species that are considered generally sensitive or tolerant to human disturbances are commonly used as indicators of healthy ecosystems or ecosystem deterioration respectively (Segurado et al., 2011;Zeni et al., 2017;Brejão et al., 2018). ...
Article
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Streams and rivers are globally threatened ecosystems due to increasing levels of exploitation, habitat degradation and other anthropogenic pressures. In the Lake Victoria Basin (LVB) in East Africa, these threats are mostly caused by unsustainable land use, however, the monitoring of ecological integrity of river systems has been hampered by a lack of locally developed indices. This study assessed the health of four rivers (Nzoia, Nyando, Sondu-Miriu and Mara) on the Kenyan side of the LVB using physico-chemical water quality parameters and a fish-based index of biotic integrity (IBI). Fish tolerance ranking was derived from principal component analysis of water quality parameters, and the concept of niche breadth (NB). The relationship between fish species and water quality parameters was examined with canonical correspondence analysis, while community metrics and stressors were evaluated through Pearson network correlation analysis. Fish species richness, trophic structures, taxonomic composition and species tolerance were used to generate the metrics for fish-based IBI. NB showed that most of the fish species were moderately tolerant to poor water. Moderately tolerant and intolerant fish species were negatively correlated with a high level of organic loading in the Mara River. Fish-based IBI scores for the rivers ranged from 26 to 34, with Sondu-Miriu scoring the lowest. Our results show that the cumulative effect of stressors can adequately rank fish species tolerance according to the disturbance gradients, and further develop regional metrics to assess river health. Despite the fact that fish communities are declining, continual management and enforcement of environmental regulations are important, with conservation and management of headwaters and low-order streams being essential while they are still species-rich.
... In addition, local governments and landowners have resisted land use controls, federal funding for 208 planning ended in 1981, and Congressional funding for Section 319 planning and implementation is insufficient. (4) Despite its objectives, CWA enforcement still focuses mostly on water quality pollution, ignoring the substantial impacts of agriculture on physical habitat structure, flow regimes, riparian zones and biota [94][95][96][97]. For example, Ohio EPA [98] detected stream biological impairment 50% of the time that chemical criteria were met. ...
Article
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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. ## See also https://today.oregonstate.edu/news/study-buffer-zones-better-regulation-needed-prevent-agricultural-pollution-rivers-streams ## This article isn't affiliated w/ any organization for RLV, although my past BC & CA postdocs contributed to my coauthorship. ## Further info: https://today.oregonstate.edu/news/study-buffer-zones-better-regulation-needed-prevent-agricultural-pollution-rivers-streams
... Awareness of critical stakeholders, including government officials, policymakers, and water managers on the value of biomonitoring should be raised (Davies and Jackson 2006;Paulsen et al. 2008;Gabriels et al. 2010;Li et al. 2010;Khundi et al. 2011;Birk et al. 2012;Anyadiegwu and Uwaezuoke 2015). Electronic media, such as television and print media, published articles, bulletins, newsletters, and contemporary social media platforms are potential avenues to target stakeholders (Morse et al. 2007). ...
Article
Worldwide, water resources have an impact on all forms of life as lotic systems are networks that interconnect water resources and land. They are important for navigation, water supplies, agriculture, recreation, and industrial development and help to regulate changes in climate and support social, spiritual, educational, and ecosystem health services. These ecosystems are, however, facing both natural and anthropogenic threats. Anthropogenic threats are driven by population increase, economic development, and catchment degradation. They are now the most threatened resources worldwide, and in Africa in particular. To design proper management strategies, the causes and impacts of the threats must be properly diagnosed. Monitoring and assessment approaches that show degradation and integrate it over time are essential to generate data and information required by water managers for decision making. Biomonitoring using macroinvertebrates is an effective tool in this regard, because it integrates causes of degradation and aquatic biotic responses to the impacts thereof. This review summarises the needs, challenges, and legal implications of biomonitoring in Africa using lessons from countries with successful biomonitoring as benchmarks.
... (c) Human activities such as forest logging, pollutant discharge and engineering construction can influence the balance between evapotranspiration and runoff, thereby changing river runoff [56] and affecting the river ecosystem. Furthermore, increasing unsustainable human activities result in the transition of the biological status of a river ecosystem from a natural state to degenerated state [62]. In conclusion, rivers located in areas with good water quality, high forest cover and low human impacts usually possess good ecosystem integrity and authenticity. ...
Article
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The establishment of protected areas for a river (PARs) is an efficient approach for the conservation of its ecosystem and biodiversity. This study selected the free-flowing Qingzhu River, located in the mountains of southwest China and one of 34 global biodiversity hotspots, as a case study. This study applied the ecosystem approach to develop a model for identifying priority conservation areas for a river (PCARs) based on integrity and authenticity. Three model elements were selected, namely streams, forest and human activity, characterized by three indicators: irreplaceability, tree cover and human activity, respectively. The spatial distributions of these indicators were overlaid according to different weights to generate a map (SCPV) of comprehensive protected value (CPV), which was used to indicate ecosystem integrity and authenticity in the study catchment. Lastly, PCARs were identified by comparing existing protected areas with the calculated SCPV. The application of the model to the Qingzhu River indicated the area of PCARs to be ~71.88 km2, accounting for 15.13% of the total PAR area. Priority reaches for protection were then identified, with many falling within the mainstem of the river in the middle and lower reaches. The total length of priority protected reaches was ~75.97 km, accounting for 49.33% of the total length of the river mainstem within Qingchuan County. This study validated the model at both the theoretical and practical level, confirming that the model is useful for facilitating the precise protection and smart management of rivers.
... 2) MMIs are developed and scored by using minimally or least-disturbed reference conditions, whereas the environmental conditions required for supporting recreational fisheries span a broad range of ecological conditions. Hughes and Gammon (1987) and Davies and Jackson (2006) described how sensitive species are replaced by more tolerant and common game fish species as the levels of anthropogenic disturbance increase. 3) RFIs include non-native game fish species, many of which are deliberately introduced, actively sought by anglers, and negatively affect native fish assemblages and the MMIs used to assess them. ...
Article
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 U.S.A. public and traditional fishery management agencies than are MMIs, which tend to be more useful for ecologists, environmentalists and environmental quality agencies.
... However, managers concerned with environmental condition as defined by regulatory statutes more often rely on indicators of "ecological health." Managers use indicators, such as dominance by pollution-tolerant organisms and other communitybased attributes to assess the effects of pollution, sedimentation, and a variety of other stressors, often acting in combination, on ecological condition of streams and rivers (Barbour et al., 2000;Davies and Jackson, 2006). Building the tools to predict condition or indicator scores under future land use and climate conditions could thus provide particular value to managers and regulators charged with meeting environmental standards, e.g., as established under the U.S. Clean Water Act. ...
Article
A continuous-variable Bayesian network (cBN) model is used to link watershed development and climate change to stream ecosystem indicators. A graphical model, reflecting our understanding of the connections between climate change, weather condition, loss of natural land cover, stream flow characteristics, and stream ecosystem indicators is used as the basis for selecting flow metrics for predicting macroinvertebrate-based indicators. Selected flow metrics were then linked to variables representing watershed development and climate change. We fit the model to data from two river basins in southeast US and the resulting model was used to simulate future stream ecological conditions using projected future climate and development scenarios. The three climate models predicted varying ecological condition trajectories, but similar worst-case ecological conditions. The established modeling approach couples mechanistic understanding with field data to develop predictions of management-relevant variables across a heterogeneous landscape. We discussed the transferability of the modeling approach.
... NatureServe and its network partners from state Natural Heritage Programs, in collaboration with a variety of agency partners, have developed methods to assess ecosystem condition, structured around the concept of ecological integrity ). Our EIA method follows a multi-metric approach similar to the Index of Biotic Integrity (Karr & Chu 1999) and Tiered Aquatic Life Use (Davies & Jackson 2006) frameworks for aquatic systems, and a variety of state-based wetland rapid assessment methods (Fennessy et al. 2007;Wardrop et al. 2013). We developed the EIA method for various data sources practical at the state level, but repeatable across ecosystems, states, and wherever applied nationally . ...
... Ten BCG attributes are defined in the BCG framework for all environments and include taxa sensitivity, organism condition, and various ecosystem functions that are responsive to taxa structure and compositional changes when exposed to major anthropogenic stressors (Davies and Jackson 2006;US EPA, 2016) (Supplemental Information Table D1). A total of 46 Caribbean coral species and three hydrozoan species with calcareous skeletons were assigned to one of the BCG attributes I-VI (herein represented by Roman numerals) based on their sensitivity or tolerance to pollution (I-V) or whether the species was non-native (VI) (Santavy et al., in review). ...
Article
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The Biological Condition Gradient (BCG) is a conceptual model used to describe incremental changes in biological condition along a gradient of increasing anthropogenic stress. As coral reefs collapse globally, scientists and managers are focused on how to sustain the crucial structure and functions, and the benefits that healthy coral reef ecosystems provide for many economies and societies. We developed a numeric (quantitative) BGC model for the coral reefs of Puerto Rico and the US Virgin Islands to transparently facilitate ecologically meaningful management decisions regarding these fragile resources. Here, reef conditions range from natural, undisturbed conditions to severely altered or degraded conditions. Numeric decision rules were developed by an expert panel for scleractinian corals and other benthic assemblages using multiple attributes to apply in shallow-water tropical fore reefs with depths <30 m. The numeric model employed decision rules based on metrics (e.g., % live coral cover, coral species richness, pollution-sensitive coral species, unproductive and sediment substrates, % cover by Orbicella spp.) used to assess coral reef condition. Model confirmation showed the numeric BCG model predicted the panel’s median site ratings for 84% of the sites used to calibrate the model and 89% of independent validation sites. The numeric BCG model is suitable for adaptive management applications and supports bioassessment and criteria development. It is a robust assessment tool that could be used to establish ecosystem condition that would aid resource managers in evaluating and communicating current or changing conditions, protect water and habitat quality in areas of high biological integrity, or develop restoration goals with stakeholders and other public beneficiaries.
... A scientific model that describes the biological responses within an aquatic ecosystem to the increasing effects of stressors as defined by Davies and Jackson (2006) and U.S. EPA (2016). ...
Technical Report
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The technical report entitled Biological and Water Quality Assessment the Middle Scioto River, Lower Olentangy River, and Selected Olentangy Tributaries 2020: Including a 50 Year Retrospective Analysis of Available Biological and Water Quality Data. Franklin and Pickaway Counties, Ohio (MBI Technical Report MBI 2022-4-6), is a major milestone in the management and assessment of rivers and streams as affected by 50 years of the implementation by the Clean Water Act (CWA) by private, local, state, and federal agencies and organizations. The scope of the report’s 2020 biological and water quality assessment, included the Scioto River mainstem between Griggs Dam in Columbus to Canal Park in Circleville, the Olentangy River mainstem from Powell Rd. to the mouth in downtown Columbus, and three Olentangy River tributaries in Columbus, two of which are part of Project Blueprint. Historical analysis of data spanning more than 50 years focused on the Scioto River in and downstream from Columbus and as affected by major municipal wastewater treatment plants, the sanitary and storm sewer systems, the hydrological dynamics, and habitat changes mostly related to dam removals through that time period. The analysis documents trends in commonly measured pollutants in water and sediment, habitat, and the fish and macroinvertebrate assemblages with the highlight being the attainment of the Exceptional Warmwater Habitat (EWH) aquatic life use designation downstream from Big Walnut Creek to Circleville.
... A score between 3 and 5 is representative of an impaired system and reflects the point where diatom assemblages change due to increased human activity (Hausmann et al., 2016). Gomphonema as a genus which tends to be located within unimpaired systems (Spaulding and Edlund, 2009), but as this information is based on the ecoregion of California as opposed to eastern Canada (Davies and Jackson, 2006), this may indicate that Gomphonema are more tolerant to poorer water quality in southern Ontario. Similarly, the Hilsenhoff Biotic Index (HBI) scores for identified 'fair' macroinvertebrate bioindicators ranged from 6 to 10, which falls within the 'Fairly Poor' to 'Very Poor' water quality categories (Mandaville, 2002). ...
Article
Freshwater systems are experiencing rapid biodiversity losses resulting from high rates of habitat degradation. Ecological condition is typically determined through identifying either macroinvertebrate or diatom bioindicator assemblages and comparing them to their known tolerance to stressors. These comparisons are typically conducted at family or genus levels depending on the availability of taxonomic keys and expertise for focal groups. The objective of this study was to test whether a more taxonomically comprehensive assessment of communities in benthic samples can provide a different perspective of ecological conditions. DNA metabarcoding was used to identify macroinvertebrates and diatoms from kick-net samples collected from sites with different habitat status. Sites with ‘good’ condition were associated with higher beta diversity as well as slightly higher directed connectance and modularity indicating higher resilience compared with ‘fair’ condition sites. Indicator value and correlation analyses used DNA metabarcoding data to detect 29 site condition indicator species consistent with known bioindicators and expected relative tolerances. DNA metabarcoding and trophic network analysis also recovered 11 keystone taxa. This study demonstrates the importance of taxonomic breadth across trophic levels for generating biotic data to study ecosystem status, with the potential to scale-up ecological assessments of freshwater condition, trophic stability, and resilience.
... While responses to anthropogenic change may be linear, aquatic communities often respond nonlinearly to environmental disturbance or increasing anthropogenic land use intensity (Rosenfield 2002, Allan 2004. Nonlinear relationships between environmental drivers and ecological responses arise when interactions among ecosystem components are not directly proportional and a high rate of change occurs abruptly over a narrow range along an environmental gradient (Allan 2004, Davies andJackson 2006). The frequency and strength of nonlinear responses are predicted to increase in aquatic ecosystems under future land use and climate change scenarios, particularly in systems already approaching existing thresholds (e.g. ...
Article
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The characteristic pattern of variation in flow magnitude, frequency, duration, timing, and rate of change defines the flow regime of rivers and streams and is a key driver of ecosystem processes in fluvial ecosystems. Understanding how freshwater biotic assemblages change across gradients of hydrology and anthropogenic-source disturbance in different streamflow regimes is crucial to managing for sustainable environmental flows and watershed conservation. We compiled long-term (1916–2016) occurrence records for fishes collected in the Ouachita-Ozark Interior Highlands and West Gulf Coastal Plain streams, together with hydrologic metrics calculated from daily streamflow data measured at USGS stream gauging stations (n = 111), to examine important drivers and thresholds for fish assemblage turnover in groundwater (GW), runoff (RO), and intermittent (INT) flow regimes. We also examined the importance of spatial gradients (latitude, longitude, elevation, drainage area) and anthropogenic-source stressors (Hydrologic Disturbance Index; HDI) for fish assemblage turnover using a gradient forest modeling approach. Watershed fragmentation was of high importance for fish assemblage turnover in RO and INT streams, while changes in dam storage were more important for fishes in GW streams. Hydrologic metrics describing seasonal and stochastic properties of daily streamflow (Mag6) were most important for fish assemblage turnover in INT streams. Timing of high flow events had significantly higher importance compared to flow magnitude, duration, and frequency metrics, especially for fish assemblages in GW and INT streams. The frequency and timing of low flow events had high importance for fish assemblage turnover across all stream flow classes, while the magnitude of low flows and the magnitude and rate of change of average flows was most important for INT stream fish assemblages. In addition to benefiting multi-species conservation and management actions through identification of local and regional flow-ecology relationships generalized across different flow regimes, the results of this study provide a better understanding of complex nonlinear threshold effects, which is critical to anticipating changes in aquatic ecosystems and communities.
... These ecosystems are also hot spots for human activity (e.g., urban development, agriculture, recreation, resource extraction, etc.) that has threatened biodiversity, decreased the prevalence of freshwater and terrestrial species, and impacted the functioning of ecosystem services, amongst other impacts (Granco et al., 2019). Ecosystem sustainability has received increasing attention from researchers concerned with the degradation of these important environmental systems (Fahrig, 2001;Davies and Jackson, 2006;Strayer and Dudgeon, 2010). However, public views about the information and findings of these studies and others can be divisive. ...
Article
Science has played a mixed role in guiding conservation and sustainability-oriented decision-making by individuals, policymakers, institutions, and governments. Not all science-based conservation and sustainability initiatives that address issues facing humanity and ecosystems and global problems have gained public support. Conservation decisions and policy prescriptions are and may be based on perceptions about and experiences with the environment, local land use, and ecosystems that may not align with or be grounded in science or evidence from experts in the field. Values, beliefs, and perceptions associated with nature play a critical role in how individuals view biodiversity conservation, sustainability, and natural resource management. This study first examines the gap between experts (scientists and other field experts) and the public (farmers and non-farmers) about the state of water and land resources, wildlife and associated habitats, and aquatic biodiversity in the Smoky Hill River Watershed in western Kansas. Second, the study examines the role that values and beliefs play in shaping environmental perceptions for farmers and non-farmers. Analysis confirms that a gap between experts and farmers/non-farmers does exist, especially with respect to the state of the Ogallala Aquifer, playas, rivers and streams, lakes and reservoirs, native grasslands, wildlife habitats, farmland, native fish populations, and wildlife species. Ordered-logistic regression analyses, meanwhile, indicate that farmer and non-farmer perceptions about the state of the local environment are influenced by traditional and self-interested values, as well as environmental values and beliefs, but less so by religiosity and political ideology. Despite broad takeaways, results exhibited heterogeneity across the farmer and non-farmer subpopulations. If environmental professionals cannot align ecological data, stakeholders’ values/perceptions, and policies, then the existing body of technical research and management on sustainability in natural and social sciences may be of little value.
... However, accumulating results from different studies suggest that metrics that detect changes in taxonomic composition (identity) tend to be more sensitive to environmental changes than those based on total richness or total abundance. Presumably, this is because both are susceptible to ecological compensatory mechanisms, such as enrichment (Davies & Jackson, 2006) and turnover , vagaries in sampling effort (dos Anjos & Zuanon, 2007;Terra et al., 2013a;Silva et al., 2016), and natural variability (Moya et al., 2011;Chen et al., 2017). ...
Article
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Stream degradation in Amazonia is outpacing our ability to effectively monitor it for three key reasons: (1) Many changes are cumulative and occur gradually; (2) Scientists have failed to clearly link anthropogenic disturbances with ecological and economic indicators of concern to decision makers and the public; (3) There are too many potential indicators to assess in a cost-effective manner. Therefore, we sought to assess congruency at three taxonomic resolutions (species, genus and family) and between assemblages (fish species and macroinvertebrate genera) and groups of taxa (fish: Characiformes and Siluriformes; macroinvertebrates: Anisoptera, Heteroptera, Odonata, Trichoptera, Zygoptera, EPT [Ephemeroptera, Plecoptera and Trichoptera] and THZ [Trichoptera, Heteroptera and Zygoptera]). To do so, we assessed taxonomic, land-use and habitat data from 92 stream sites in the eastern Amazonian state of Pará. We found that anthropogenic disturbances of our sites influenced abundance and incidence of macroinvertebrate and fish taxa, but the two assemblages responded to slightly different stressors. Family and genera levels were suitable substitutes for similarity patterns measured at the macroinvertebrate genera and fish species levels, respectively. Odonata, Trichoptera, EPT and THZ were highly congruent with whole macroinvertebrate assemblage (genus level) variation. Characiformes was also congruent with whole fish assemblage (species level) variation. Congruence among macroinvertebrates and fish was intermediate (55% to 79%) and related to differing responses to environmental variables. Our results suggest that some groups (e.g., Odonata, Trichoptera and Characiformes) are useful surrogates of macroinvertebrate or fish assemblages to evaluate anthropogenic disturbance in Amazonian streams.
... Studies have applied the use of lower species dominance and higher species richness of macroinvertebrates as reference indicators for disturbed environments [63,64]. From this study, the greater dominance of species that is, Chironomus and T. tubifex in areas with depleted riparian buffer (stations 1 and 2), suggests a proliferation of opportunistic species due to varied sensitivity of macroinvertebrates under gradients of pollution. ...
Article
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Riparian vegetation and built-up density along the urbanised section of the Calabar river were estimated using NDVI (Normalised Differential Vegetation Index) and NDBI (normalised differential built-up index), respectively. Four sampling stations representing riparian density and built-up gradients i.e. Station 1 (sparse riparian + high-density built-up), 2 (sparse riparian + high to intermediate-density built-up), 3 (moderate riparian + intermediate to low-density built-up) and station 4 (moderate riparian + low-density built-up) were selected. Station-specific variations of metal (Pb, Cd, Cr, Fe and Cu) in surface water and benthic macro-invertebrate communities were examined between January and December 2013 and correlated using redundancy analysis (RDA). Buffer analysis revealed that stations having low NDBI with over 120 m dense riparian areas showed a marked abundance of muddy/coarse substrate while sparse riparian areas showed siltier and sandier substrate. Redundancy analysis revealed a marked delineation of macroinvertebrate occurrence with the riparian density of stations. High diversity macroinvertebrate assemblages showed a strong positive association with alkaline pH, the density of riparian vegetation and substrate type. This first report highlights the critical relationship between riparian density, water quality and benthic macroinvertebrates in a tropical river. ARTICLE HISTORY Highlights. Urbanisation depletes the density of riparian vegetation. Degraded watersheds were assessed using spectral indices. Substrate-type and water quality strongly correlate with the riparian density. Depleted riparian buffer exposes surface water to contaminant-laden runoff. Water quality and substrate type affected the occurrence of species diversity
... Naturalness and integrity are often judged by historical fidelity (connectivity in time), a full complement of native species, characteristic species dominance and productivity, presence of typical ecological processes such as fire, flooding, and windstorms, and minimal evidence of anthropogenic stressors . This information can be used to set levels of ecological integrity along a gradient from minimally disturbed conditions to severely impacted sites (Davies and Jackson 2006). Given the extensive loss or alteration of ecosystems in many jurisdictions, current ecological conditions may only include conditions that are outside the NRV. ...
Chapter
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This chapter provides an introduction to "Conserving Biodiversity on Military Lands – A Guide for Natural Resources Managers, 3rd Edition". The chapter describes what biodiversity is, how it is faring across the United States, and the role that military lands play in conserving the nation's biodiversity. The chapter also describes DoD's evolving approach to conservation and natural resource management and how effective biodiversity conservation is key to sustaining military readiness. The chapter ends with a discussion of recent trends in military biodiversity conservation, including a focus on broader landscape collaborations, innovation in endangered species recovery, and climate change adaptation and resilience.
... In order to facilitate the landscape planning and the ecological restoration of the riparian zone, a standard should be established. Scholars proposed the concept of reference systems to define and describe the real state of the riparian zone under natural conditions [42][43][44]. However, rivers flowing through the cities are likely to be regarded as artificial landscapes to provide other functions as well compared to other rivers. ...
Article
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Vegetated buffer zones (VBZ) are accepted worldwide as a low impact method to avoid non-point source pollution and restore the balance of river ecosystems. Strongly influenced by industrialization and urbanization, urban river ecology is seriously damaged, and restoration is tricky. This study established a complete buffer zone construction framework suitable for the small urban watershed, and its feasibility is verified in a small watershed in Northern China. First, common plants in the study area were selected to test their ability to purify pollutants, and plant combinations were optimized. Secondly, according to the field investigation, the reference buffer zone was determined, and its sewage interception capacity was tested through a runoff simulation experiment. Then, based on GIS and Phillips time and hydraulic models, the normal buffer width of the study area was obtained; 60 m for mainstream and 40 m for tributaries. By optimizing the vegetation scheme and delimiting an efficient buffer zone, the land occupation can be reduced by 17%. Finally, combined with the characteristics of different river sections, an elaborate VBZ restoration scheme is designed from the aspects of vegetation, planning, and zoning. Generally, this research will provide government and land managers scientific and practical ideas and technologies to formulate a land management policy for urban river buffer zones in order to find a balance between aquatic ecological protection and urban land use planning and optimize the allocation of construction funds.
... Approaches in this toolkit should also protect particular levels on the "biological condition gradient", as used in the USA (Davies and Jackson, 2006;Charles et al., 2021). It is also possible to derive nutrient boundaries from ecological data without the need to summarise the latter as a metric (e.g. ...
Article
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... We believe these results from the same processes that make measures of taxonomic richness, diversity, evenness, and specialization relatively insensitive measures of disturbance. For example, sensitive taxa respond to low levels of disturbance before tolerant taxa, but at moderate levels of disturbance the sensitive taxa are replaced by tolerant taxa, thereby resulting in no change-or even increased-total taxa richness (Brito et al., 2020; Davies and Jackson, 2006;Oliveira-Junior et al., 2017). Those same responses affect total taxonomic diversity, evenness, and specialization, which is why such metrics alone have tended to be less frequently employed in rigorous biomonitoring programs (Chen et al., 2019;Silva et al., 2017;Stoddard et al., 2008). ...
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Biomonitoring is an essential tool for assessing ecological conditions and informing management strategies. The application of DNA metabarcoding and high throughput sequenc-ing has improved data quantity and resolution for biomonitoring of taxa such as macroinvertebrates, yet, there remains the need to optimise these methods for other taxo-nomic groups. Diatoms have a longstanding history in freshwater biomonitoring as bioindi-cators of water quality status. However, multi-substrate periphyton collection, a common diatom sampling practice, is time-consuming and thus costly in terms of labour. This study examined whether the benthic kick-net technique used for macroinvertebrate biomonitoring could be applied to bulk-sample diatoms for metabarcoding. To test this approach, we collected samples using both conventional multi-substrate microhabitat periphyton collections and bulk-tissue kick-net methodologies in parallel from replicated sites with different habitat status (good/fair). We found there was no significant difference in community assemblages between conventional periphyton collection and kick-net methodologies or site status, but there was significant difference between diatom communities depending on site (P = 0.042). These results show the diatom taxonomic coverage achieved through DNA metabarcoding of kick-net is suitable for ecological biomonitoring applications. The shift to a more robust sampling approach and capturing diatoms as well as macroinvertebrates in a single sampling event has the potential to significantly improve efficiency of biomonitoring programmes that currently only use the kick-net technique to sample macroinvertebrates.
Chapter
Threats to inland water insects can only be appraised realistically in the wider perspective of threats to freshwater biodiversity and are dominated by changes to their habitats from human activities. The major threats to freshwater ecosystems are driven by human population growth associated with anthropogenic climate change which itself exacerbates previously less intensive threats such as fire and vegetation removals.
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This paper describes our efforts to integrate economic and biophysical models to evaluate the effects agri-environmental policies have on the value of freshwater ecosystem services. We are developing an integrated assessment model (IAM) that links changes in phosphorus-related management practices on farm fields to changes in the value of key freshwater ecosystem services, including biological condition, water clarity, species-specific fish biomasses, and beach algae. Our IAM approach enables examination of the effects of policies and conservation programs on ecosystem services and values. Results will help policy makers allocate conservation dollars to improve water quality, enhance ecosystem services, and promote more sustainable agricultural production. (JEL Q24, Q51) © 2020. by the Board of Regents of the University of Wisconsin System. All Rights Reserved.
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Se consideró relevante monitorear y caracterizar la calidad del agua en un tramo del río Uruguay, utilizando diatomeas, como bioindicadoras, su relación con factores fisicoquímicos y plaguicidas, en un ciclo anual. Los máximos valores de los parámetros fisicoquímicos y DBO se registraron en su mayoría en La Verde, Benito Lejerén y Yuquerí Chico. Por otro lado, las diatomeas determinadas en estos sitios, fueron tolerantes a altos niveles de contaminación, demostrando así, que son excelentes bioindicadoras de la calidad del agua. Se identificaron 285 taxones distribuidos en los géneros Nitzschia, Navicula, Gomphonema, entre otros. El índice de Diatomeas Pampeano, resultó apropiado para la evaluación de la calidad de agua en este tramo del río. Sin embargo, en algunos sitios se encontró dominancia de especies que no cuentan con un valor asignado de IDP, por lo tanto, se plantea la necesidad de elaborar un nuevo índice local. Se determinó la presencia de plaguicidas organoclorados a lo largo de todo el año, alcanzando niveles muy elevados en el cuarto muestreo. Resulta importante, que los programas de monitoreo de calidad de agua se complementen además, con la incorporación de bioindicadores, lo cual, sería de gran utilidad para el asesoramiento del estado trófico de ríos.
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Human impacts on stream ecosystems are expected to intensify with population growth and climate change. Decisive information on how stream communities respond to cumulative human impacts is therefore integral for protecting streams draining multi-use catchments. To determine cumulative influences of nutrient enrichment and assess more nuanced approaches for the evaluation of human impacts, we present results from one factorial and two gradient assessment designs applied to benthic algae and macroinvertebrate data from 14 mid-order streams in southern Ontario, Canada with pre-existing human impacts (i.e., sewage effluent and agriculture). We found that among stream variability in ecological indicators measured downstream of sewage effluent outfalls confounded our generalized factorial assessment and provided inconclusive information on a known human impact. Despite our gradient assessment also not having strong statistical support, accounting for the extent of nutrient enrichment associated with differences in sewage effluent and agricultural inputs revealed that larger longitudinal changes in stream communities were associated with increased nutrient enrichment. However, re-weighting our nutrient enrichment gradient based on upstream nutrient concentrations to account for nonlinearities in the response of stream communities to nutrient enrichment produced more robust assessment results that were consistent with predicted effects of nutrients on stream ecosystems. Thus, while our factorial assessment suggests that the communities are resistant to nutrients from cumulative human impacts, our targeted gradient assessment demonstrates that the effects of nutrient enrichment are highly conditional on upstream ecosystem conditions. Future assessments may need to go beyond traditional approaches (i.e., impact presence/absence) and more explicitly consider the environmental stressors and their associated complexities related to the impact under investigation.
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Few ecotoxicity studies are available on thorium (Th) which hinders the ability to evaluate its ecotoxicological risk. Its release in the environment is often associated with the extraction of rare earth elements and uranium, as well as the field applications of phosphate fertilizers. This study investigates the effects of Th on microbial communities of periphytic biofilms. Ceramic plates were left to colonize for one month in the laboratory with a biofilm sampled from Cap Rouge river (QC, Canada). Plates were randomly placed in channels containing culture media representing three different conditions: a control condition (C0; background Th concentrations of 0.004 ± 0.002 nM), a low Th concentration condition (C1; 0.18 ± 0.09 nM Th) and a moderately high Th condition (C10; 8.7 ± 3.4 nM) for up to 4 weeks. The presence of Th modified the diatom community by changing its taxonomic structure, reducing diversity and increasing cell density. The taxonomic structure of the bacterial community, followed by 16S metabarcoding analysis, was affected with a significant decrease in Pseudanabaena and Shingopyxis genera in the two Th exposed conditions. No direct toxic effect of Th was observed on counted micromeiofauna but the changes in diatom and bacterial communities could explain the higher number of individual diatoms and micromeiofauna observed in Th-exposed conditions. This work shows that low concentrations of Th can modify biofilm structure, which, in turn, could disturb its ecologically key functions.
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The Santa Margarita River (SMR) watershed encompasses approximately 750 square miles in northern San Diego and southwestern Riverside counties. Urban and agricultural land uses in the watershed result in modified flow and increased nutrient supply to the mainstem of the River and the estuary, resulting in eutrophication in some reaches, defined as the increase in the rate of supply and/or in situ production of organic matter (from aquatic plants) in a water body. Several river and tributary reaches and the SMR estuary were listed on the 2010 Clean Water Act (CWA) section 303(d) list of water quality limited segments as impaired for biostimulatory substances and conditions linked to eutrophication. The listings were based on exceedances of a specific numeric interpretation of the biostimulatory narrative objective in the Water Quality Control Plan for the San Diego Basin for nitrogen and phosphorus that were established in 1975. The availability of more recent scientific advances provides a more modern scientific framework with which to evaluate the effects on water quality and beneficial uses from biostimulatory substances and conditions. The goal of this report is to synthesize information to support stakeholder conversations and Water Board management actions to support SMR watershed beneficial uses. Specifically, this includes: • Synthesis of the scientific lines of evidence supporting decisions on biostimulatory targets, specifically for TN, TP, dissolved oxygen, and organic matter accumulation, expressed as algal biomass (benthic chlorophyll-a) and ash-free dry mass (AFDM). • Analyses of how climate change can impact SMR flow and temperature regimes that will alter nutrient loading and other biostimulatory conditions and influence biological integrity. • Analyses of load allocations by land use and jurisdiction that correspond with Water Board proposed biostimulatory targets in the SMR main stem and how this compares to previously established allocations for the Santa Margarita River Estuary (SMRE).
Chapter
Aim: This chapter introduces the standard DPSIR model for managing impact and how the measurement of an impact requires a reference condition, or baseline, with which to compare its current state. Establishing the baseline is essential for measuring the current state of the ecosystem. The reference state provides a form of anchoring against which the health of an ecosystem is estimated, for setting targets of what might be the limits of acceptable change, or to guide ambitions for restoration. Main concepts covered: The DPSIR model of environmental management and importance of a reference state; defining and distinguishing concepts of reference state; methods for deciding a reference state, and uncertainties of that; the use of reference state in policy and management; shifting perceptions of reference state; and implications of reference state for management. Main methods covered: Historical records for Reference description, including those from the landscape and sediment of lakes; Different approaches to the estimation of baselines and reference state; Judgment of experts and shifting baselines; and baseline from first monitoring and associated risks. Conclusion/Synthesis: An assessment of anthropogenic impact of a waterbody requires an estimate of a reference value under no or minimal impact. This allows judgement of the extent of impact, but can be practically difficult to do. It is, therefore, important to clearly define and describe whatever methods are used to assess the baseline condition.
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Here we present two multiproxy records covering the last 5000 years from the Akrotiri Marsh in southern Cyprus. Pollen and diatom analysis of radiocarbon dated marsh sediments with an average chronological resolution of one date every thousand years, reveal expansion and contraction of the marsh in response to mid-late Holocene climate events, with peak aridity reconstructed in the early Bronze Age, inferred between 4.3 and 4.1 cal ka BP, and repeated dry intervals in the Late Bronze Age, inferred between 3.4 and 3.1 cal ka BP. The record provides important contextual climate data to the debate surrounding reported Early and Late Bronze Age societal collapse events present in numerous archaeological archives throughout the Mediterranean and Near Eastern region. This is the first multiproxy record from the island of Cyprus potentially displaying the 4.2 ka BP event. The characteristics of the inferred 3.2 ka BP event are very similar to the manifestation of the event in the east of Cyprus and on the southern Levantine mainland. These results contribute to the regional understanding of Bronze Age climates on Cyprus, give insight into the expression of global climate forcing mechanisms such as the North Atlantic Oscillation and the Siberian High, and provide potential evidence for reduced anthropogenic land-use during the 4.2 ka BP and 3.2 ka BP Events supporting what is documented in archaeological archives.
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Since recorded time, rivers have facilitated the establishment of human civilizations because of the myriad ecosystem goods and services they offer (Macklin and Lewin, 2015). Rivers provide transportation corridors, supply food in form of fisheries, and are major sources of water for irrigation, domestic use, renewable energy, and industrial development (Ripl, 2003). However, these benefits have come at a great cost to the structural and functional integrity of rivers and linked ecosystems (Dudgeon et al., 2006; Vörösmarty et al., 2010). The capacity of rivers to sustainably meet human needs for water and ecosystem services is premised on maintaining their ecological integrity, which encompasses the gamut of biological diversity and ecosystem processes that maintain them (Karr, 1993). In river networks, ecological integrity is spatiotemporally dynamic, largely driven by the natural flow regime (Poff et al., 1997), which provides a template for ecological processes and species to thrive. River managers have the challenge of reconciling human needs with the ecological requirements of healthy ecosystems. This requires innovative decision-support tools for assessing and monitoring the ecological status of rivers to guide management and conservation efforts. This Research Topic presents selected original research articles and reviews on some of the tools used to assess the ecological status of rivers in Africa. The objectives of the special issue are to: i. contribute to the development of biomonitoring tools (e.g., biotic indices, multimeric indices, models, etc.), that are affordable, rapid and easy to use for enhanced understanding of human impacts on rivers. ii. give novel insights into the effects of multiple stressors in rivers arising from human activities, such as land-use change, water pollution and excessive water withdrawals, iii. address methodological challenges related to the use of existing tools used for biomonitoring, and iv. encourage knowledge sharing and standardization of tools used for biomonitoring rivers in Africa, and promote interdisciplinary collaborations.
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The establishment of quantitative targets for algal abundance in lakes (usually expressed as water column chlorophyll a concentration in μg/L) is well‐ensconced in lake management. Setting targets for abundance of benthic/attached algae in streams has not garnered as much attention in stream ecology and management. Establishment of targets for benthic algae in streams is in part dependent upon the particular attribute that is to be protected, including water withdrawal/water supply, aesthetics, recreation, or ecosystem protection. Abundance targets may be expressed as % cover, chlorophyll a density (as mg Chl a per unit area), or standing crop (g dry weight or ash‐free dry weight per unit area). This chapter will review benthic algal abundance targets proposed in the stream literature and compare them with epiphytic and macroalgal abundance measured in a 2015 study of 14 spring‐run streams in Florida. Various investigators have proposed quantitative targets based on either mean/median or maximum algal abundance. Efforts in temperate streams have suggested macroalgal targets of 20%–40% cover, 100–150 mg/m 2 chlorophyll a density, or 40 g/m 2 ash‐free dry weight (AFDW). These targets were mainly based on aesthetics and recreational issues and may or may not be relevant for Florida spring‐run streams, but they may be adopted as a starting point. Given the changes in benthic algal abundance seen in Florida spring‐run streams over the past few decades, establishing targets for algal abundance to guide restoration attempts appears to be warranted.
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A study of two watersheds in central Pennsylvania, an undisturbed forested (reference) one and a partially disturbed (agricultural and residential) one, was used to analyze how agriculture and residential development of the riparian corridor affected species richness, abundance, and the structure of guilds of the bird community. Bird species richness and abundance generally decreased with distance from the stream in the disturbed watershed, but remained relatively constant through the reference watershed. At disturbed sites most neotropical migrant birds with specific habitat requirements were recorded only during migration. Although an impoverished bird community can exist in the vicinity of the riparian band immediately adjacent to the water with <10 m (30 ft) of natural vegetation, sensitive species will not occur unless an undisturbed corridor >25 m (82 ft) in width on each bank is present. Presence of narrow 2 m (7 ft) bands of woody vegetation along the stream channel and fence rows seemed to be important in maintaining portions of the bird community in disturbed areas. Land owners and resource managers should be aware of responses by the avian community to small, incremental changes in land use, and try to protect existing stream corridors or restore native vegetation in riparian areas.
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Fish communities were sampled at 14 sites along the lower 120 km of the Fraser River, British Columbia by beach seine four times in 1972–1973 and three times in 1993–1994. Of the 37 species collected, peamouth chub, largescale sucker, starry flounder, and northern squawfish were predominant in either density or biomass. Densities and biomass of most species and all fish combined were higher in 1993–1994. Strong rank correlations of species abundance or biomass indicated that the overall fish community structure was very similar in both periods. At smaller spatial scales (reaches of 2–3 sites) and shorter time scales (by season), less than half the comparisons showed any significant correlation indicating changes in community composition. Largescale sucker, one of the largest contributors to biomass in both periods, showed decreased abundance, i.e., lower density, lower biomass, and large differences in the size-frequency distribution, specifically very low representation of small size classes. Other species, especially small-bodied forms, generally increased in numbers. Despite large changes in the lower Fraser River ecosystem in the past 21 years, the overall fish community has shown remarkably little change over that interval.
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Metrics characterizing the benthic macroinvertebrate assemblages in wadeable streams in the Mid-Atlantic region of the United States were analyzed to explore the relative responses of the metrics to different types of anthropogenic stress. The data used in our study were collected by the US Environmental Protection Agency Environmental Monitoring and Assessment Program from 1993 to 1996. Regression models were developed relating metric values at reference sites to natural sources of variability. These models were then used to predict reference values at test sites. Test site metric observations were scaled by subtracting the predicted reference value and dividing by the standard deviation of residuals at reference sites. Stressor–response relationships for each scaled metric were then estimated using generalized additive models. Metric responses to 4 groups of stressors (nutrient enrichment, habitat degradation, elevated metals concentrations, and elevated ion concentrations) were different. The proportional abundance of tolerant taxa was the most sensitive indicator of nutrient enrichment and habitat degradation, whereas Ephemeroptera richness was the most sensitive indicator of elevated metals or ion concentrations.
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Understanding variation in the freshwater production of Atlantic salmon across its range is a critical aspect of the species' conservation, restoration, and management. We focus on how environmental factors operate at four hierarchical scales (region, watershed, reach, local habitat) to influence the production and survivorship of juvenile salmon and the production of their invertebrate food base. Using published, quantitative information about invertebrate production in small, cold streams characteristic of Altantic salmon nursery streams, we estimate expected maximum salmon production will be ca. 9 (range 6-22) g wet mass m(-2) year(-1), which compares favorably with reported literature values of <1 to 17 g m(-2). We highlight some empirically based, shortcut approaches to estimating invertebrate production that may be particularly useful for evaluating salmonid production across a range of scales. We also consider how availability of invertebrate prey may influence salmon production. As a synthesis, we integrate existing information into a multi-scale framework by making qualitative predictions (hypotheses) about expected patterns of invertebrate and salmon production at different habitat scales. We then develop quantitative, heuristic scenarios that predict (hypothesize) how salmon and invertebrate production will change in response to selected physicochemical and non-trophic habitat limitations operating at the watershed (geology, land use) and reach (channel form, canopy) scales. Predicted values, which fall within the range of observed values for Atlantic salmon streams, demonstrate that a multi-scale habitat perspective can provide important insights into local to regional variation in the production of Atlantic salmon across its range and thus contribute to Atlantic salmon conservation, restoration, and management.
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Man's impact on his environment often involves a gradient of subsidy and stress effects, which vary along nutrient, climatic, developmental (successional), and other important ecological gradients. Since performance curves that simulate subsidy-stress responses are unimodal, the zone of optimality can be determined on the basis of relatively few experiments where specific input factors are of concern. We have emphasized the importance of assessing the response of the perturbed system at different levels of organization. In practice, at least two levels, the ecosystem and the population (species) level, are necessary for a complete impact evaluation. We have stressed the need for judicious use of terms and the desirability of sticking as closely as possible to basic dictionary definitions if one expects to communicate with large numbers of people. Most of all, we have tried to show how a systems approach, based on simple flow diagram models, can clarify the intended meaning of terms and the cause-and-effect relations, as well as identify the basic processes involved.
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Road construction of the Redwood National Park highway bypass resulted in a large accidental infusion of fine sediments into pristine streams in Prairie Creek State Park, California, during an October 1989 storm event. This incident provided a natural experiment where we could measure, compare, and evaluate native stream amphibian densities as indicators of stream ecosystem stress. We employed a habitat-based, stratified sampling design to assess the impacts of these sediments on the densities of aquatic amphibians in five impacted streams by comparing them with densities in five adjacent, un-impacted (control) streams. Three species were sampled in numbers sufficient to be informative: tailed frogs (Ascaphus truei, larvae), Pacific giant salamanders (Dicamptodon te-nebrosus, paedomorphs and larvae), and southern torrent salamanders (Rhyacotriton var-iegatus, adults and larvae). Densities of amphibians were significantly lower in the streams impacted by sediment. While sediment effects were species specific, reflecting differential use of stream microhabitats, the shared vulnerability of these species to infusions of fine sediments is probably the result of their common reliance on interstitial spaces in the streambed matrix for critical life requisites, such as cover and foraging. Many stream-dwelling amphibians are highly philopatric and long-lived, and they exist in relatively stable populations. These attributes make them more tractable and reliable indicators of potential biotic diversity in stream ecosystems than anadromous fish or macroinvertebrates, and their relative abundance can be a useful indicator of stream condition.
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Man's activities have had profound, and usually negative, influences on freshwater fishes from the smallest streams to the largest rivers. Some negative effects are due to contaminants, while others are associated with changes in watershed hydrology, habitat modifications, and alteration of energy sources upon which the aquatic biota depends. Regrettably, past efforts to evaluate effects of man's activities on fishes have attempted to use water quality as a surrogate for more comprehensive biotic assessment. A more refined biotic assessment program is required for effective protection of freshwater fish resources. An assessment system proposed here uses a series of fish community attributes related to species composition and ecological structure to evaluate the quality of an aquatic biota. In preliminary trials this system accurately reflected the status of fish communities and the environment supporting them.
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Assessment of the condition of ecosystems is a critical prerequisite for al- leviating effects of the multiple anthropogenic stresses imposed on them. For stream eco- systems, a multitude of approaches has been proposed for this purpose. However, they all rest on the assessment of structural attributes, even though it is generally recognized that adequate characterization of ecosystems requires information on both structure (pattern) and function (process). Therefore, we propose a complementary approach to stream as- sessment based on evaluating ecosystem-level processes. Leaf litter breakdown is a prime candidate to consider in this context. This is because of the pivotal role that allochthonous litter plays in streams, the demonstrated effects of anthropogenic perturbations on litter breakdown, and the relative ease of implementation. Leaf breakdown is governed by a variety of internal and external factors that complicate the partitioning of effects due to anthropogenic stress and natural variability (background noise), thus potentially limiting the sensitivity and robustness of litter breakdown assays. However, internal regulation factors can be controlled by standardizing assessment procedures, while variability due to external factors can be accounted for by stream classification and/or a comparative approach (e.g., downstream-upstream comparisons). Composite parameters such as ratios of break- down rates in fine-mesh and coarse-mesh bags may further increase the power of litter breakdown assays. Analyses may also be extended to include both leaf-associated decom- poser assemblages (i.e., structural measures) and processes (i.e., additional functional mea- sures). Significant efforts are required for developing standard assessment schemes as re- fined as extant procedures based on structural stream attributes (e.g., structure of macroin- vertebrate assemblages). These efforts are nevertheless worthwhile in view of the new dimension that is added to current assessment procedures when functional elements are
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The rapid spread of the exotic zebra mussel (Dreissena polymorpha) concerns aquatic resource managers in the United States and Canada. Since 1990, it has been spreading from the Great Lakes into the Northeast. The zebra mussel cannot colonize equally in northeastern lakes in part because soft water causes ion exchange and reproductive problems when [Ca] reaches a lower limit of approximately 12 mg/L, and pH drops below 7.3. We used (1) an alkalinity map to conservatively delineate areas expected to be at low risk for zebra mussel invasion and (2) water chemistry data from 344 lakes sampled in the 1991–1994 Environmental Monitoring and Assessment Program (EMAP) to estimate numbers and surface area of lakes at risk in the Northeast (New England, New York, and New Jersey). These lakes were randomly selected from a target population of 11,080 lakes > 1 and < 10,000 ha using a probability design that allowed inference to all lakes in the region with known confidence. An estimated 25% (2,770 SE = 410) of lakes in the Northeast have [Ca] > 12 mg/L and could potentially support zebra mussel. An estimated 80% of lakes in high alkalinity areas are at risk, while only 5% of lakes in low alkalinity areas have [Ca] > 12 mg/L. The alkalinity map adequately segregated low- and high-calcium lakes. State resource managers can use this information to better allocate control, monitoring, and education resources.
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We describe a general process for developing an index of fish assemblage integrity, using the Willamette Valley of Oregon, U.S.A., as an example. Such an index is useful for assessing the effects of humans on entire fish assemblages, and the general process can be applied to any biological assemblage and any region. First, a reference condition was determined from historical information, and then candidate metrics of ecological importance were listed. The variability of the candidate metrics in time and space was estimated and their responsiveness to independent measures of riparian and stream habitat quality assessed. Metrics were scored continuously from 0 to 10, producing an index of biological integrity (IBI) that was weighted to range from 0 to 100 regardless of the number of metrics. The index, developed from a set of 35 sites, was then tested on an independent set of eight urban sites sampled by the Oregon Department of Fish and Wildlife. Thirteen of the 16 candidate metrics were appropriate and produced an IBI with among-site variance triple that of revisit variance. The method distinguished sites with acceptable fish assemblages from marginally and severely impaired sites.
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Biological monitoring in its most rudimentary fonn probably had its origin in the minds of fish wardens, river keepers, and minders of lakes and ponds. Anyone living near a water body has a sense of biomonitoring, although not necessarily a scientifically rigorous one. Sentinel human noses have smelled septic hydrogen sulfide at remarkably good analytical levels. Aristotle, who is credited with dabbling in nearly every known area of modem science, is known to have placed freshwater fish in salt water to observe their reactions . We define biological monitoring as surveillance using the responses of Jiving organisms to determine whether the environment is favorable to living material. Biological monitoring is not new, as the king's wine taster attests. In the early days of the industrial revolution, canaries were kept in underground coal mines. If a canary showed adverse reactions to conditions in the mine, the miners left. Biological monitoring also implies quality control · in which some corrective action will be taken if expected conditions are not met; but the existence of a feedback mechanism that involves a response to indications of failed environmental health is problematic in most countries.
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Fish assemblages integrate physical and chemical habitat conditions and are used to evaluate the condition of water resources in the Pacific Northwest. To facilitate such evaluations, we classified each of the 132 freshwater fish species known to occur in the Pacific Northwest (Idaho, Oregon, Washington) by its origin, overall pollution tolerance, adult habitat, adult feeding, and water temperature preference. Recommendations from regional fishery experts, published literature, and the aggregate experience of the authors were used to classify species. The attribute classifications were responsive to human disturbance of aquatic habitats when applied to fish assemblages sampled from throughout the region. Our attribute classification of fish species promotes use of fish assemblages to evaluate water resource conditions regionally and fosters greater acceptance of biological measures of water resource quality.
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We assessed the effects of nonnative fish on native fish biodiversity, using assemblage data collected during 1991-1996 from 203 randomly selected lakes in the northeastern USA by the Environmental Monitoring and Assessment Program (EMAP) of the U.S. Environmental Protection Agency. An estimated 74% (± 17.6%, 95% confidence interval) of the region's 10,608 lakes between I and 10,000 ha contain at least one introduced species. Based on our samples, nonnative individuals outnumbered natives in an estimated 31.5% (± 11%) of lakes. Regression models indicated that native, introduced, and total species richness were associated with lake surface area, elevation, and lake depth (0.31 ≤ R2 ≤ 0.81). The intensity of human disturbance in the watershed was positively associated with introduced species richness but not associated with native species richness. The number of nonnative species was a significant variable in the native-species regression models for the entire Northeast and for only ode of five subregions, the Northeast Coastal Zone ecoregion. Of the types of fishes that have been introduced, littoral predators - primarily Micropterus - appeared to have the greatest negative effect on native species richness. Small or soft-tinned species appeared to be the least tolerant of these introduced predators. Native brook trout and minnow assemblages, typical of northern lakes in the Northeast but now rare in the Adirondacks, appeared to be at the greatest risk from continued introductions in northeastern New England. Current among-lake (β) species diversity was associated more with regional diversity of lake types than with extent or dominance of nonnative species. Without quantitative historical data, it was not possible to demonstrate a homogenizing effect of introductions on lake fish assemblages.
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Abiotic variation, including changed water chemistry and habitat structure, has a strong impact on all trophic levels. Low pH increased toxicity of metals, especially aluminium, the abiotic factors affect both the top-down and bottom-up forces, and changes can be triggered at all trophic levels. A second force structuring the community is a bottom-up effect caused by reduced nutrient cycling and a shift in plant heterogeneity. This shift, mainly resulting from a shift in the CO2-system of the water and increased water transparency, enhances the biomass of primary producers eg Sphagnum and Juncus, and alters habitat heterogeneity in higher trophic levels. The third force structuring the acid community is a top-down effect; the loss of the fourth link in the food chain (fish) alters the impact on the third trophic level. From being mainly regulated by predation from fish, the heterogeneity of the third level will be regulated by abiotic variation and competition in the acid state. This effect cascades down the food web, and the second trophic level, the herbivores, will now be preyed upon by vertebrates instead of fish. -from Authors
Chapter
The transplantation of fishes has a long history in Western culture, beginning with the Romans, who brought carp (Cyprinus carpio) from the Danube River to Italy (Balon 1975). As Christianity spread throughout Europe, carp entered local fish communities, initially as escapees from monastery ponds. More deliberate colonizations were made in Scandinavia, where the introduction of indigenous salmonids into alpine lakes was apparently a regular practice by the 12th century A.D. (Nilsson 1972). Small-scale introductions continued until the 1840s, when the discovery, in France, of artificial propagation techniques for fish made introductions possible on a much larger scale (Regier and Applegate 1972). The idea of enhancing wild fish populations through the introduction of hatchery-reared fish quickly spread to North America and by the 1870s private, state, and federal fish hatcheries were common. The most important species reared at this time was the carp, which by 1890 was found throughout North America, thanks to the development of railroads and fish transport cars. Other species were raised as well, however, so that by 1873 a railroad car containing 300,000 fish of 10 species was on its way to California (Sheeley 1917). Such cars usually carried Pacific coast salmonids back to the eastern seaboard on the return trip. This practice of taxon redistribution (Regier and Applegate 1972) continues to the present time, not only with fish but with other aquatic organisms as well (e.g., Carlton 1974).
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(1) The effects of river regulation on river margin vegetation were evaluated by comparing two parallel seventh order rivers, one natural and the other strongly regulated, in northern Sweden. Prior to regulation, both rivers had similar vegetation. (2) No difference between the natural and the regulated river was found in width and height (relative to the summer low-water level) of the river margin, number of substrates, and mean annual discharge. (3) Frequency distributions of species differed in that the regulated river had fewer frequent and more infrequent species. Species-richness and the percentage cover of vegetation were both lower per site in the regulated river. The proportion of annual plus biennial species-richness was higher and that of perennial species-richness lower along the regulated river. (4) Reservoirs retaining pre-regulation river margins and remnants of their former vegetation, and stretches with a modest flow regulation, were most floristically similar to the natural river. (5) Regression equations including eight independent variables explained 10-77% of the variation in species-richness in thirteen groups of plants and in plant cover for two vegetation layers. Presence of pre-regulation river margin vegetation, water-level regime, height of the river margin, and mean annual discharge were the most important variables for species-richness, while water-level regime, mean annual discharge and substrate fineness were most important for plant cover. (6) In most cases, values of species-richness were higher in natural sites and in regulated sites with remnants of pre-regulation river margin vegetation, whereas they decreased with increasing height of the river margin. Percentage cover of ground vegetation was highest in natural sites with a fine-grade substrate.
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A number of studies have documented tolerance in aquatic communities exposed to contaminants, but few have examined costs of tolerance and potential community-level consequences. We assessed the effects of metals and acidic pH, a novel stressor, on communities from streams with different histories of metal pollution. Acidic pH was a novel stressor to communities in streams that are consistently circumneutral. Intact benthic invertebrate assemblages collected from metal-polluted sites on the Arkansas River (AR1, low levels of pollution, and AR5, greater levels of pollution) and a reference site on the Cache la Poudre River (PR), Colorado, were exposed to either metals (Zn, Cu, Cd) or pH 4.5 in stream microcosms. Multivariate analyses on a subset of taxa showed different patterns of response to metals and acidic pH among the 3 sites, which corresponded to exposure histories of the communities: PR assemblages were more sensitive to metals, whereas AR assemblages were more sensitive to acidic pH. These patterns were supported by analyses on specific characteristics of community structure. Exposure to metals significantly reduced abundance of mayfly taxa in PR (p = 0.0041, ANOVA, linear contrast), AR1 (p = 0.0108), and AR5 (p = 0.0329) assemblages and taxa abundance in PR (p = 0.0225) and AR1 (p = 0.0469) assemblages. Total invertebrate abundance also decreased in PR assemblages exposed to metals (p = 0.0274). The results suggested that greater metal tolerance within the Arkansas River communities was a result of assemblage-level differences in community structure and population-level differences in sensitivity among sites. In contrast, Arkansas River assemblages, especially those from AR5, were sensitive to acidic pH, which reduced invertebrate abundance in PR (p = 0.0339), AR1 (p = 0.0284), and AR5 (p = 0.0062) assemblages. Abundances of mayflies and mayfly taxa also were significantly lower in AR1 (p = 0.0247, p = 0.0042, respectively) and AR5 (p
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Recent research is reviewed from books, international committees and symposia which describes the usefulness of biological monitoring for exposure to such compounds as organometallic chemicals, carbon monoxide and cyanide. The types of analyses include the following measurements: the concentration of the chemical in various biological media such as blood, urine, and expired air; the concentration of metabolites of the individual chemical in the same media; and determination of nonadverse biological changes resulting from the reaction of the organism to exposure. A main goal of such monitoring is to ensure that the current or past levels of worker exposure are safe, so that such exposure does not involve an unacceptable health risk. It considers routes other than absorption by the lungs and is a good method for evaluating individual exposures.
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We assessed the effects of nonnative fish on native fish biodiversity, using assemblage data collected during 1991–1996 from 203 randomly selected lakes in the northeastern USA by the Environmental Monitoring and Assessment Program (EMAP) of the U.S. Environmental Protection Agency. An estimated 74% (±17.6%, 95% confidence interval) of the region's 10,608 lakes between 1 and 10,000 ha contain at least one introduced species. Based on our samples, nonnative individuals outnumbered natives in an estimated 31.5% (±11%) of lakes. Regression models indicated that native, introduced, and total species richness were associated with lake surface area, elevation, and lake depth (0.31 ≤ R ≤ 0.81). The intensity of human disturbance in the watershed was positively associated with introduced species richness but not associated with native species richness. The number of nonnative species was a significant variable in the native-species regression models for the entire Northeast and for only one of five subregions, the Northeast Coastal Zone ecoregion. Of the types of fishes that have been introduced, littoral predators—primarily Micropterus—appeared to have the greatest negative effect on native species richness. Small or soft-finned species appeared to be the least tolerant of these introduced predators. Native brook trout and minnow assemblages, typical of northern lakes in the Northeast but now rare in the Adirondacks, appeared to be at the greatest risk from continued introductions in northeastern New England. Current among-lake (β) species diversity was associated more with regional diversity of lake types than with extent or dominance of nonnative species. Without quantitative historical data, it was not possible to demonstrate a homogenizing effect of introductions on lake fish assemblages.