Biological Condition Gradient Research Articles

Fuzzy logic as a novel approach to predict biological condition gradient of various streams in Ceyhan River Basin (Turkey)

Creating a method to categorize the ecological status of streams according to their biological conditions and establishing scientifically defensible nutrient criteria to protect their biotic integrity poses significant challenges. Biomonitoring of least disturbed areas is an important issue to accurately assess the ecological status of surface waters and ensure their sustainability. The fuzzy logic as a novel approach was firstly applied to evaluate the biological condition gradient of 44 sampled streams in the Ceyhan River Basin, utilizing two diatom indices, total phosphorus (TP), electrical conductivity (EC), and CORINE data. The fuzzy logic was employed to examine variations in the diatom compositions and land cover based on biological condition gradients (BCGs) of various streams and to assess the suitability of BCG in evaluating the health of studied stream systems. A three-layer fuzzy logic was constructed to predict BCGs of steams based on input data, with diatom metrics, TP, and EC representing BCGdia and land cover variables contributing to BCGland. The effects of operating variables were studied to optimize BCG results. The highest BCG score (0.85) was determined in Aksu Spring Brook in the spring, whereas the lowest value (0.05) was calculated in Erkenez Stream3 in the summer. BCGs showed strong relationships with nutrients, altitude, and EC. Results of BCGs indicated that sampling stations have various ecological statuses ranging from bad to high in the Ceyhan River Basin. The BCGdia and BCGland made important contributions to determine the ecological status of streams in the Ceyhan River Basin. Results showed that the BCG approach allows a more reliable way to determine the ecological status of streams in the Ceyhan River Basin by combining biological and chemical assessments for the sustainability of the environment. It is recommended that the BCG will be applied and evaluated in future research studies across various river basins, both within and outside of Turkey.

Valuing improvements in the ecological integrity of local and regional waters using the biological condition gradient

Scientific knowledge related to quantifying the monetized benefits for landscape-wide water quality improvements does not meet current regulatory and benefit-cost analysis needs in the United States. In this study we addressed this knowledge gap by incorporating the Biological Condition Gradient (BCG) as a water quality metric into a stated preference survey capable of estimating the total economic value (use and nonuse) for aquatic ecosystem improvements. The BCG is grounded in ecological principles and generalizable and transferable across space. Moreover, as the BCG translates available data on biological condition into a score on a 6-point scale, it provides a simple metric that can be readily communicated to the public. We applied our BCG-based survey instrument to households across the Upper Mississippi, Ohio, and Tennessee river basins and report values for a range of potential improvements that vary by location, spatial scale, and the scope of the water quality change. We found that people are willing to pay twice as much for an improvement policy that targets their home watershed (defined as a four-digit hydrologic unit) versus a more distant one. We also found that extending the spatial scale of a local policy beyond the home watershed does not generate additional benefits to the household. Finally, our results suggest that nonuse sources of value (e.g., bequest value, intrinsic aesthetic value) are an important component of overall benefits.

A biological condition gradient for coral reefs in the US Caribbean Territories: Part I. Coral narrative rules

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.

A biological condition gradient for Caribbean coral reefs: Part II. Numeric rules using sessile benthic organisms.

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.

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

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

Using the Biological Condition Gradient Model as a Bioassessment Framework to Support Rehabilitation and Restoration of the Upper Tana River Watershed in Kenya

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.

Development of fish-based indices of biological integrity for Minnesota lakes

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.

Development of a reef fish biological condition gradient model with quantitative decision rules for the protection and restoration of coral reef ecosystems

Coral reef ecosystems are declining due to multiple interacting stressors. A bioassessment framework focused on stressor-response associations was developed to help organize and communicate complex ecological information to support coral reef conservation. This study applied the Biological Condition Gradient (BCG), initially developed for freshwater ecosystems, to fish assemblages of U.S. Caribbean coral reef ecosystems. The reef fish BCG describes how biological conditions changed incrementally along a gradient of increasing anthropogenic stress. Coupled with physical and chemical water quality data, the BGC forms a scientifically defensible basis to prioritize, protect and restore water bodies containing coral reefs. Through an iterative process, scientists from across the U.S. Caribbean used fishery-independent survey data and expert knowledge to develop quantitative decision rules to describe six levels of coral reef ecosystem condition. The resultant reef fish BCG provides an effective tool for identifying healthy and degraded coral reef ecosystems and has potential for global application.

Characterizing benthic macroinvertebrate and algal biological condition gradient models for California wadeable Streams, USA

Abstract The Biological Condition Gradient (BCG) is a conceptual model that describes changes in aquatic communities under increasing levels of anthropogenic stress. The BCG helps decision-makers connect narrative water quality goals (e.g., maintenance of natural structure and function) to quantitative measures of ecological condition by linking index thresholds based on statistical distributions (e.g., percentiles of reference distributions) to expert descriptions of changes in biological condition along disturbance gradients. As a result, the BCG may be more meaningful to managers and the public than indices alone. To develop a BCG model, biological response to stress is divided into 6 levels of condition, represented as changes in biological structure (abundance and diversity of pollution sensitive versus tolerant taxa) and function. We developed benthic macroinvertebrate (BMI) and algal BCG models for California perennial wadeable streams to support interpretation of percentiles of reference-based thresholds for bioassessment indices (i.e., the California Stream Condition Index [CSCI] for BMI and the Algal Stream Condition Index [ASCI] for diatoms and soft-bodied algae). Two panels (one of BMI ecologists and the other of algal ecologists) each calibrated a general BCG model to California wadeable streams by first assigning taxa to specific tolerance and sensitivity attributes, and then independently assigning test samples (264 BMI and 248 algae samples) to BCG Levels 1–6. Consensus on the assignments was developed within each assemblage panel using a modified Delphi method. Panels then developed detailed narratives of changes in BMI and algal taxa that correspond to the 6 BCG levels. Consensus among experts was high, with 81% and 82% expert agreement within 0.5 units of assigned BCG level for BMIs and algae, respectively. According to both BCG models, the 10th percentiles index scores at reference sites corresponded to a BCG Level 3, suggesting that this type of threshold would protect against moderate changes in structure and function while allowing loss of some sensitive taxa. The BCG provides a framework to interpret changes in aquatic biological condition along a gradient of stress. The resulting relationship between index scores and BCG levels and narratives can help decision-makers select thresholds and communicate how these values protect aquatic life use goals.

The use of multiscale stressors with biological condition assessments: A framework to advance the assessment and management of streams

Incorporating information on landscape condition (or integrity) across multiple spatial scales and over large spatial extents in biological assessments may allow for a more integrated measure of stream biological condition and better management of streams. However, these systems are often assessed and managed at an individual scale (e.g., a single watershed) without a larger regional multiscale context. In this paper, our goals were: (1) To develop a conceptual framework that could combine stream biological condition to abiotic landscape integrity (or, conversely, stressor) data at three spatial scales: watershed, catchment and stream-reach scale, to enable more targeted management actions. Measures of landscape integrity and stressors are negatively related, i.e., integrity on a 0–1 scale is equal or equivalent to stressors on a 1–0 scale. (2) To develop the framework in such a way that allows operational flexibility, whereby different indicators can be used to represent biological condition, and landscape integrity (or stressors) at various scales. (3) To provide different examples of the framework's use to demonstrate the flexibility of its application and relevance to management. Examples include stream biological assessments from different regions and states across the U.S. for fish, macroinvertebrates and diatoms using a variety of assessment tools (e.g., the Biological Condition Gradient (BCG), and an Index of Biotic Integrity (IBI)). Landscape integrity indicators comprise U.S. EPA's nationally available Index of Watershed Integrity (IWI) and Index of Catchment Integrity (ICI), and state and regional derived watershed and stream-reach scale integrity indicators. Scatterplots and a landscape integrity map were used to relate samples of stream condition classes (e.g., good, fair, poor) to watershed, catchment and stream-reach scale integrity. This framework and approach could provide a powerful tool for prioritizing, targeting, and communicating management actions to protect and restore stream habitats, and for informing the spatial extent at which management is applied.

Use of diatoms for developing nutrient criteria for rivers and streams: A Biological Condition Gradient approach

Nutrient enrichment is one of the most important causes of ecological impairment in surface waters. More effective management of this problem is constrained by a lack of nutrient criteria that link phosphorus and nitrogen concentrations to levels of biological impairment as defined in management agency regulations. We used a new approach for identifying potential nutrient criteria using diatom assemblages and the Biological Condition Gradient (BCG). We first used diatom count data to assign study sites to BCG impairment categories (levels), then determined P and N concentrations corresponding with the boundaries between those levels. We studied diatom counts and environmental data from 95 river and stream sites throughout the state of New Jersey (NJ), USA. The sites represent five ecoregions, primarily forested uplands and coastal plains, and a wide range of nutrient concentrations (total P range of 15 to >200 µg L−1 and total N 0.5 to >4 mg L−1). Advantages of NJ as a study region are the ready availability of streams with a large gradient in nutrient concentrations and similarity to nutrient-stressed systems in many other geographic regions. BCG levels represent a range of ecological conditions from natural to highly impaired. A panel of experts on use of diatoms as ecological indicators assigned 57 study sites to BCG levels based on diatom assemblage composition. Potential nutrient criteria were subsequently derived by determining the measured TP and TN concentrations associated with the boundary between impaired sites and non-impaired sites (BCG levels greater than 4). Based on this approach, statewide criteria of no greater than 50 µg L−1 TP and 1.0 mg L−1 TN are indicated for maintaining or restoring sites to unimpaired condition. In some least-disturbed ecoregions, lower concentrations (e.g., 25 µg L−1 of TP) would be more appropriate to maintain current ecological conditions. Existing diatom TP and TN metric values for the study sites correlate well with BCG level assignments and can be used to determine if nutrient criteria are met. Overall, results demonstrate the usefulness of data derived from diatom assemblages in management of nutrient issues, and the potential widespread applicability of the BCG approach to develop nutrient criteria and to monitor compliance.

Calibration of the biological condition gradient in Minnesota streams: a quantitative expert-based decision system

AbstractThe Biological Condition Gradient (BCG) is a conceptual model that describes changes in aquatic communities with increasing levels of anthropogenic stress. The gradient represented by the BCG has been divided into 6 levels of condition that biologists consider readily discernible in most areas of North America. We developed quantitative BCG models for 7 warm-water stream types in Minnesota for both fish and macroinvertebrates. Panels of aquatic biologists calibrated the general BCG model to Minnesota streams by assigning test samples (271 macroinvertebrate and 288 fish samples) to BCG Levels 1 to 6. From the panelists’ descriptions of their criteria for assigning sites to levels, a set of quantitative operational rules was developed for performing the same task. We developed a decision model based on fuzzy-set theory to account for discontinuities and to identify when BCG assignments might be intermediate between adjacent levels. This model captures the consensus professional judgment of the panel...

A diatom-based biological condition gradient (BCG) approach for assessing impairment and developing nutrient criteria for streams

Over-enrichment leading to excess algal growth is a major problem in rivers and streams. Regulations to protect streams typically incorporate nutrient criteria, concentrations of phosphorus and nitrogen that should not be exceeded in order to protect biological communities. A major challenge has been to develop an approach for both categorizing streams based on their biological conditions and determining scientifically defensible nutrient criteria to protect the biotic integrity of streams in those categories. To address this challenge, we applied the Biological Condition Gradient (BCG) approach to stream diatom assemblages to develop a system for categorizing sites by level of impairment, and then examined the related nutrient concentrations to identify potential nutrient criteria.The six levels of the BCG represent a range of ecological conditions from natural (1) to highly disturbed (6). A group of diatom experts developed a set of rules and a model to assign sites to these levels based on their diatom assemblages. To identify potential numeric nutrient criteria, we explored the relation of assigned BCG levels to nutrient concentrations, other anthropogenic stressors, and possible confounding variables using data for stream sites in New Jersey (n=42) and in surrounding Mid-Atlantic states, USA (n=1443). In both data sets, BCG levels correlated most strongly with total phosphorus and the percentage of forest in the watershed, but were independent of pH. We applied Threshold Indicator Taxa Analysis (TITAN) to determine change-points in the diatom assemblages along the BCG gradient. In both data sets, statistically significant diatom changes occurred between BCG levels 3 and 4. Sites with BCG levels 1 to 3 were dominated by species that grow attached to surfaces, while sites with BCG scores of 4 and above were characterized by motile diatoms. The diatom change-point corresponded with a total phosphorus concentration of about 50μg/L.

A novel approach for the development of tiered use biological criteria for rivers and streams in an ecologically diverse landscape.

Water resource protection goals for aquatic life are often general and can result in under protection of some high quality water bodies and unattainable expectations for other water bodies. More refined aquatic life goals known as tiered aquatic life uses (TALUs) provide a framework to designate uses by setting protective goals for high quality water bodies and establishing attainable goals for water bodies altered by legally authorized legacy activities (e.g., channelization). Development of biological criteria or biocriteria typically requires identification of a set of least- or minimally-impacted reference sites that are used to establish a baseline from which goals are derived. Under a more refined system of stream types and aquatic life use goals, an adequate set of reference sites is needed to account for the natural variability of aquatic communities (e.g., landscape differences, thermal regime, and stream size). To develop sufficient datasets, Minnesota employed a reference condition approach in combination with an approach based on characterizing a stream's response to anthropogenic disturbance through development of a Biological Condition Gradient (BCG). These two approaches allowed for the creation of ecologically meaningful and consistent biocriteria within a more refined stream typology and solved issues related to small sample sizes and poor representation of minimally- or least-disturbed conditions for some stream types. Implementation of TALU biocriteria for Minnesota streams and rivers will result in consistent and protective goals that address fundamental differences among waters in terms of their potential for restoration.

Applicability and Interpretation of Fish Indices of Biotic Integrity (IBI) for Bioassessment in the Upper Midwest

AbstractMultiple fish‐based indices of biotic integrity (IBIs) and biological condition gradient models have been developed and validated to assess ecological integrity in the Laurentian Great Lakes region. We evaluated the applicability and effectiveness of using fish community indices for assessing site integrity in central Great Lakes streams, which have diverse temperature regimes and can be classified as warmwater, coolwater, or coldwater. Sites with different thermal regimes require different assessment tools to ensure comparability. Streams in the Big Manistee River watershed, Michigan, are near thermal thresholds for classification as coolwater or coldwater. We evaluated two coolwater and three coldwater indices developed for Upper Midwest streams. Output from coolwater indices were not correlated with coldwater index outputs and did not discriminate among the stream systems we evaluated. In monitoring temporal patterns over time (2002–2010), we found that coldwater indices showed similar patterns and agreed in relative scoring of sites from high to low. The three coldwater indices also similarly discriminated among stream systems; however, when the coldwater indices were used for specific site assessments, they produced differential results. Depending on which index was applied, a single site could be classified into three different levels of quality. This highlights the importance of index selection for management actions. An understanding of the factors that drive the indices and an understanding of reference conditions are imperative for effective use of fish‐based IBIs in the Upper Midwest.Received July 15, 2014; accepted December 12, 2014

A biological condition gradient model for historical assessment of estuarine habitat structure.

Coastal ecosystems are affected by ever-increasing natural and human pressures. Because the physical, chemical, and biological characteristics unique to estuarine ecosystems control the ways that biological resources respond to ecosystem stressors, we present a flexible and adaptable biological assessment method for estuaries. The biological condition gradient (BCG) is a scientific framework of biological response to increasing anthropogenic stress that is comprehensive and ecosystem based and evaluates environmental conditions and the status of ecosystem services in order to identify, communicate, and prioritize management action. Using existing data, we constructed the first estuarine BCG framework that examines changes in habitat structure through time. Working in a New England (U.S.) estuary with a long history of human influence, we developed an approach to define a reference level, which we described as a "minimally disturbed" range of conditions for the ecosystem, anchored by observations before 1850 AD. Like many estuaries in the U.S., the relative importance of environmental stressors changed over time, but even qualitative descriptions of the biological indicators' status provided useful information for defining condition levels. This BCG demonstrated that stressors rarely acted alone and that declines in one biological indicator influenced the declines of others. By documenting the biological responses to cumulative stressors, the BCG inherently suggests an ecosystem-based approach to management. Additionally, the BCG process initiates thinking over long time scales and can be used to inspire scientists, managers, and the public toward environmental action.

Evaluation of suitability and comparability of stream assessment indices using macroinvertebrate data sets from the Northern Lakes and Forests Ecoregion

Researchers and managers within the Upper Midwest currently use a variety of sampling methodologies and biological indices to assess ecological condition of stream systems. With multiple entities collecting bioassessment data it is important that we determine the comparability of data and the indices derived from these data for effective assessment of natural systems. In this study we assessed the similarity of data collected by different agencies and we focused on data from one watershed to examine the outputs of different indices for stream assessment, and the temporal variation of index score within sites. We compared duplicate macroinvertebrate community data collected by the Little River Band of Ottawa Indians and the Michigan Department of Environmental Quality for overall community composition and index scores derived from these data. Duplicate samples were similar in composition index scores. Taxonomic resolution was addressed and indicated that genus level resolution gives a more favorable score when using indices. We also evaluated the utility of currently available macroinvertebrate indices of biotic integrity to assess data from the Big Manistee River watershed. The indices evaluated were the Hilsenhoff biotic index, the benthic community index for the Northern Lakes and Forests (NLFBCI), the Great Lakes Environmental Assessment Survey (GLEAS) procedure 51 for macroinvertebrates and a biological condition gradient model for the Upper Midwest. Outputs from the indices were moderately correlated (Spearman rank order correlation, r=0.35–0.698) though they indicated different assessments of overall site integrity. Compared with larger scale regional indices, locally calibrated indices generally classified sites as having better biological condition. Replicate samples collected within sites indicated the GLEAS had higher levels of variability (0–265%CV) within sites than the other indices (<10%CV). Data from long-term (10 year) monitoring stations were used to evaluate seasonal and long-term index performance. There were differences in index score classifications from spring and fall samples indicating that standardization of sampling time is necessary for comparative analysis. Temporal trends over 10 years reveal natural variation and set the baseline for evaluating the influence of anthropogenic effects. Overall, results indicate that choice of index can alter assessment of site condition. For bioassessment in the Big Manistee River watershed the NLFBCI performs well and accurately reflects site condition.

Application of multiple index development approaches to benthic invertebrate data from the Virginian Biogeographic Province, USA

Previous work had indicated that the Virginian Province Index did not perform well in a smaller estuarine complex. While it was hoped that the existing Chesapeake Bay Benthic Index of Biotic Integrity, with its greater number of metrics and habitat separation would be more adaptable, this index also did not perform well outside of Chesapeake Bay. In this study we assembled additional metrics and applied different methods of index compilation to explore the indices relative strengths and weaknesses. Three different approaches were utilized – two multimetric indices (Chesapeake Bay IBI and the Mebane IBI) and a statistical logistic regression technique. The data were subdivided by habitat (salinity and grain size), and indices compiled using the same initial group of benthic metrics. Each approach was examined for its classification accuracy for both reference and impaired sites for the entire Virginian Province. The Chesapeake Bay IBI approach did not perform well in this study. In contrast, another multimetric approach, the Mebane IBI approach, performed well, as did the statistical logistic regression approach. Both techniques have promise for index development and could be useful in applying a biological condition gradient to estuaries.

An algal model for predicting attainment of tiered biological criteria of Maine's streams and rivers

State water-quality professionals developing new biological assessment methods often have difficulty relating assessment results to narrative criteria in water-quality standards. An alternative to selecting index thresholds arbitrarily is to include the Biological Condition Gradient (BCG) in the development of the assessment method. The BCG describes tiers of biological community condition to help identify and communicate the position of a water body along a gradient of water quality ranging from natural to degraded. Although originally developed for fish and macroinvertebrate communities of streams and rivers, the BCG is easily adapted to other habitats and taxonomic groups. We developed a discriminant analysis model with stream algal data to predict attainment of tiered aquatic-life uses in Maine's water-quality standards. We modified the BCG framework for Maine stream algae, related the BCG tiers to Maine's tiered aquatic-life uses, and identified appropriate algal metrics for describing BCG tiers. Using a modified Delphi method, 5 aquatic biologists independently evaluated algal community metrics for 230 samples from streams and rivers across the state and assigned a BCG tier (1–6) and Maine water quality class (AA/A, B, C, nonattainment of any class) to each sample. We used minimally disturbed reference sites to approximate natural conditions (Tier 1). Biologist class assignments were unanimous for 53% of samples, and 42% of samples differed by 1 class. The biologists debated and developed consensus class assignments. A linear discriminant model built to replicate a priori class assignments correctly classified 95% of 150 samples in the model training set and 91% of 80 samples in the model validation set. Locally derived metrics based on BCG taxon tolerance groupings (e.g., sensitive, intermediate, tolerant) were more effective than were metrics developed in other regions. Adding the algal discriminant model to Maine's existing macroinvertebrate discriminant model will broaden detection of biological impairment and further diagnose sources of impairment. The algal discriminant model is specific to Maine, but our approach of explicitly tying an assessment tool to tiered aquatic-life goals is widely transferrable to other regions, taxonomic groups, and waterbody types.

Implications of global change for the maintenance of water quality and ecological integrity in the context of current water laws and environmental policies

There is both a fundamental and applied need to define expectations of changes in aquatic ecosystems due to global changes. It is clear that programs using biological indicators and reference-based comparisons as the foundation for assessments are likely to make increasingly erroneous decisions if the impacts of global change are ignored. Global changes influence all aspects of water resource management decisions based on comparisons to reference conditions with impacts making it increasingly problematic to find an “undisturbed” water body to define acceptable conditions of ecological integrity. Using a more objective scale for characterizing reference conditions that is anchored in expectations for what would be attainable under undisturbed conditions, such as the Biological Condition Gradient (BCG) is one approach that maintains consistent definitions for ecosystem conditions. In addition, protection of reference stations and of unique or undisturbed aquatic resources is imperative, though the scope of protection options is limited. Projections indicate that encroaching land use will affect 36–48% of current reference surface waters by the year 2100. The interpretation of biological indicators is also at risk from global changes. Distinguishing taxonomic attributes based on temperature or hydrologic preferences can be used to enhance the ability to make inferences about global change effects compared to other stressors. Difficulties arise in categorizing unique indicators of global changes, because of similarities in some of the temperature and hydrologic effects resulting from climate change, land use changes, and water removal. In the quest for biological indicators that might be uniquely sensitive to one global stressor as an aid in recognizing probable causes of ecosystem damage, the potential similarities in indicator responses among global and landscape-scale changes needs to be recognized as a limiting factor. Many aspects of global changes are not tractable at the local to regional scales at which water quality regulations are typically managed. Our ability to implement water policies through bioassessment will require a shift in the scale of assessment, planning, and adaptations in order to fulfill our ultimate regulatory goals of preserving good water quality and ecological integrity. Providing clear expectations of effects due to global change for key species and communities in freshwater ecosystems will help water quality programs achieve their goals under changing environmental conditions.