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Background Eutrophication of freshwater ecosystems resulting from nitrogen and phosphorus pollution is a major stressor across the globe. Despite recognition by scientists and stakeholders of the problems of nutrient pollution, rigorous synthesis of scientific evidence is still needed to inform nutrient-related management decisions, especially in streams and rivers. Nutrient stressor-response relationships are complicated by multiple interacting environmental factors, complex and indirect causal pathways involving diverse biotic assemblages and food web compartments, legacy (historic) nutrient sources such as agricultural sediments, and the naturally high spatiotemporal variability of lotic ecosystems. Determining nutrient levels at which ecosystems are affected is a critical first step for identifying, managing, and restoring aquatic resources impaired by eutrophication and maintaining currently unimpaired resources. The systematic review outlined in this protocol will compile and synthesize literature on the response of chlorophyll a to nutrients in streams, providing a state-of-the-science body of evidence to assess nutrient impacts to one of the most widely-used measures of eutrophication. This review will address two questions: “What is the response of chlorophyll a to total nitrogen and total phosphorus concentrations in lotic ecosystems?” and “How are these relationships affected by other factors?” Methods Searches for published and unpublished articles (peer-reviewed and non-peer-reviewed) will be conducted using bibliographic databases and search engines. Searches will be supplemented with bibliography searches and requests for material from the scientific and management community. Articles will be screened for relevance at the title/abstract and full text levels using pre-determined inclusion criteria; 10% (minimum 50, maximum 200) of screened papers will be examined by multiple reviewers to ensure consistent application of criteria. Study risk of bias will be evaluated using a questionnaire developed from existing frameworks and tailored to the specific study types this review will encounter. Results will be synthesized using meta-analysis of correlation coefficients, as well as narrative and tabular summaries, and will focus on the shape, direction, strength, and variability of available nutrient-chlorophyll relationships. Sensitivity analysis and meta-regression will be used to evaluate potential effects of study quality and modifying factors on nutrient-chlorophyll relationships.

When an environmental impairment has been identified, it becomes necessary to identify the cause so that an appropriate action can be planned. However, causation is difficult to establish—both conceptually and in practice. To ensure that the U.S. Environmental Protection Agency's (USEPA's) method for causal assessment is appropriate and defensible, we reviewed concepts of causation from philosophers, statisticians, epidemiologists, and others. This article summarizes the results of that review and explains how it relates to the USEPA's method. We include a five-step process: (1) identify alternative candidate causes; (2) logically eliminate when possible; (3) diagnose when possible; (4) analyze the strength of evidence for remaining candidate causes; and (5) identify the most likely cause. We also encourage three practices: (1) use a consistent process; (2) do not claim proof of causation; and (3) document the evidence and inferences. This approach allows assessors to identify the most likely cau...

The United States Environmental Protection Agency (USEPA) has ongoing programs to encourage the evaluation of stream conditions based on biological indicators. Bioassessments reveal impairments but do not identify causes of impairments, a necessary step in the restoration of aquatic life. Furthermore, changes in biological condition are often caused by multiple stressors (chemical, physical, biological). To address this need, the USEPA has developed guidance to identify probable causes of biological impairments in aquatic ecosystems and to provide a structure for organizing the scientific evidence to make a credible case. The concepts and organizational structure of the process have potential applications to most ecoepi-demiological investigations.

The risk assessment framework presented in the National Research Council (NRC) Red Book played a key role in the development of ecological risk assessment (ERA). ERA frameworks have, however, developed along their own pathway and have significantly extended concepts that were introduced in the Red Book. When the U.S. Environmental Protection Agency (EPA) commissioned the Oak Ridge National Laboratory (ORNL) in 1981 to develop and apply methods for ERA, the work focused on probabilistic analysis, since that seemed to be the essence of risk. When the Red Book appeared, it suggested that the use of a logical framework to guide the process was also an important aspect of risk assessment. Therefore, the ORNL investigators developed a framework similar to the Red Book framework but more suited to ERA. When EPA initiated a project to develop an official EPA framework for ERA, the ORNL framework was presented in a colloquium intended to obtain input from scientists outside EPA. Later, the NRC sponsored a workshop...

Interest in causal investigations in aquatic systems has been a natural outgrowth of the increased use of biological monitoring to characterize the condition of resources. Although biological monitoring approaches are critical tools for detecting whether effects are occurring, they do not identify the cause of the observed effects. Formal approaches to causal evaluation can provide a mechanism to build on expert knowledge, increasing the likelihood that remedial efforts will achieve the desired environmental improvement. This paper examines how formal approaches to causal investigations minimize common errors. We reviewed common cognitive errors reported in the literature, and compared them with considerations suggested for strength-of-evidence approaches. Many of the causal considerations are directed toward distinguishing spurious correlations from true causal relationships. However, this is only one type of error; others include hypothesis dependence, confirmation bias, hypothesis tenacity and anchorin...

This review assesses the state of the science on the effects of mountaintop mines and valley fills (MTM-VF) on the physicochemical characteristics of streams in the central Appalachian coalfields of West Virginia, Kentucky, Virginia and Tennessee, USA. We focus on the impacts of mountaintop removal coal mining, which involves removing all - or some portion - of the top of a mountain or ridge to expose and mine one or more coal seams. Excess overburden is disposed in constructed fills in small valleys adjacent to the mining site. MTM-VF leachate persistently increases the downstream concentrations of major ions. Conductivity is a coarse measure of these ions, which are dominated by a distinct mixture of SO(4)(2-), HCO(3)(-), Ca(2+) and Mg(2+), that reflects their source, the oxidation of pyrite to form acid followed by neutralization of the acidity by carbonate minerals within the valley fills. This results in neutral to alkaline pHs, a range at which many metals are relatively insoluble. Other compounds within coal or overburden are solubilized and occur at elevated albeit lower concentrations, including K(+), Na(+), Cl(-), Se and Mn. In terms of physical characteristics, the valley fills act like headwater aquifers, baseflows increase in streams below valley fills and water temperatures exhibit reduced seasonal variation. Peak discharges may be increased in response to intense precipitation events, because of compaction of base surfaces of the MTM-VF areas, but newer approaches to reclamation reduce this compaction and may ameliorate these peak flows. Although the sedimentation pond is intended to capture fine particles that wash downstream from the valley fill, some studies found increased fine sediments in streams downstream from valley fills. However, a proportion of these fines may be eroded from stream banks rather than the valley fills. This is probably a result of the alterations in stream flows.

Ecological risk assessment is becoming an increasingly important tool for ranking, assessing, reducing, and managing environmental risks. To pro- vide Agency-wide guidance in this area in the U.S., EPA's Risk Assessment Forum has begun a multi-year guidelines development program. The first step in this program was the publication of the report “Framework for Ecological Risk Assessment” which describes the principles, concepts, terminology, and structure of ecological risk assessments.

Water quality monitoring data are usually used independently to report on the condition of streams and watersheds. For example, watersheds are often rated as good, fair, or poor with regard to a single stressor or with regard to an index of biotic integrity. The utility of monitoring data may be enhanced by integrating stressor-response information with the observed stressor data, and reporting stressor levels in terms of their relative effects upon valued ecological resources. We estimated stressor-response relationships at the regional scale using data collected in the Eastern Cornbelt Plains Ecoregion of Ohio. Generalized additive models were used to visualize stressor-response relationships. Piecewise linear functions and simple linear functions were then used to parameterize the observed responses. Parameters derived from the regional models were used to scale observations of stressors in the Big Darby Creek watershed, OH. After scaling, stressors were compared in terms of their spatial distribution and in terms of the severity with which they influenced the biological endpoint of interest. Stressors most strongly associated with the current ecological condition of the watershed were identified. In the Big Darby Creek watershed, decreases in substrate quality were associated with the most severe decrements in biological condition. At smaller decrements in biological condition, three stressors were important: substrate quality, riparian quality, and increased concentrations of NOx.