Modernizing thermal discharge assessments for the 21st century.

A jointly prepared, interagency (US Environmental Protection Agency [USEPA] and the US Nuclear Regulatory Commission [USNRC]), §316(a) Technical Guidance Manual has been the primary guide to ecological studies of thermal discharges at power plants since 1977. It reflected contemporary ecological theory, which assumed that undisturbed populations and ecosystems possessed a balanced and relatively unchanging structure and function that could be disrupted by addition of heat from a thermal discharge. It was intended primarily to facilitate the licensing of proposed nuclear power plants and thus focused on predictive assessments. Since 1977, however, scientific and regulatory contexts of §316(a) assessments have changed. Ecologists abandoned the notion of "balance" in populations and ecosystems and now recognize that natural systems are always changing spatially and temporally. Regulatory emphasis has shifted from predictive assessments at new plants, largely based on thermal-tolerance laboratory data, to retrospective assessments based on field data at operating plants. We suggest updates to thermal-assessment studies based on modern ecological theory and recent thermal-assessment practice. The concepts we outline are fully consistent with statutory language and may assist in design and implementation of study plans by applicants and their consultants, development of discharge permits by USEPA or state agencies, and reviews of assessment documents by interested public and environmental organizations. Integr Environ Assess Manag 2022;18:459-468. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Integration of ecosystem science into radioecology: A consensus perspective.

In the Fall of 2016 a workshop was held which brought together over 50 scientists from the ecological and radiological fields to discuss feasibility and challenges of reintegrating ecosystem science into radioecology. There is a growing desire to incorporate attributes of ecosystem science into radiological risk assessment and radioecological research more generally, fueled by recent advances in quantification of emergent ecosystem attributes and the desire to accurately reflect impacts of radiological stressors upon ecosystem function. This paper is a synthesis of the discussions and consensus of the workshop participant's responses to three primary questions, which were: 1) How can ecosystem science support radiological risk assessment? 2) What ecosystem level endpoints potentially could be used for radiological risk assessment? and 3) What inference strategies and associated methods would be most appropriate to assess the effects of radionuclides on ecosystem structure and function? The consensus of the participants was that ecosystem science can and should support radiological risk assessment through the incorporation of quantitative metrics that reflect ecosystem functions which are sensitive to radiological contaminants. The participants also agreed that many such endpoints exit or are thought to exit and while many are used in ecological risk assessment currently, additional data need to be collected that link the causal mechanisms of radiological exposure to these endpoints. Finally, the participants agreed that radiological risk assessments must be designed and informed by rigorous statistical frameworks capable of revealing the causal inference tying radiological exposure to the endpoints selected for measurement.

Quantifying Restoration Offsets at a Nuclear Power Plant in Canada.

In Canada, the Fisheries Act requires all water takers to avoid, mitigate and offset fish losses. To satisfy the act's requirements, operators of power plants are required to undertake habitat restoration projects to compensate for fish impinged and entrained at cooling water intake structures. Scaling the quantity of restoration needed, and measuring whether adequate compensation has been achieved, requires a metric that expresses the losses and gains in comparable units. Development of such a metric is especially difficult in the case of power plants, because the losses often consist of a mix of species and life stages that are very different from those produced by technically feasible restoration projects. This paper documents the method that has been developed for quantifying offsets for impingement and entrainment at the Bruce Generating Stations on the eastern shore of Lake Huron, and demonstrates how the method is being used to estimate the offset to be provided by removal of a dam on the nearby Saugeen River.

Assessing and Managing Natural Resource Damages: Continuing Challenges and Opportunities.

In a 2002 paper, we discussed the technical challenges associated with quantifying natural resource injuries, service losses and damages, and suggested some actions that might help to overcome them. An important suggestion was to consider using some of the approaches in ecological risk assessment to help evaluate potential natural resource injuries, and ultimately in some cases to help translate those injuries into natural resource service loss. This was based on the observation that ecological risk assessment and natural resource damage assessments use much of the same types of data, but at that time the experience base with ecological risk assessment was greater than for natural resource damage assessments. We also discussed some of the issues in applying the then current Department of Interior natural resource damage assessments regulations. Since our 2002 publication the scientific literature, relevant regulations, the global context and more have changed. In the current paper we focus on the technical and regulatory changes in natural resource damage assessments practice since 2002, and use recent reports and publications to illustrate those changes and identify new directions in natural resource damage assessments.

Polychlorinated biphenyls and Hudson River white perch: implications for population-level ecological risk assessment and risk management.

Risk assessments and risk management decisions concerning risks to wild fish populations resulting from exposures to polychlorinated biphenyls (PCBs) and related chemicals have been based primarily on observations of effects of chemicals on individual organisms. Although the development and application of population-level ecological risk-assessment methods is proceeding at a rapid pace, the organism-level approach is still being justified by arguments that population-level ecological risk assessment is in an early stage of development and has not been shown to be reliable. This article highlights the importance of including population-level effects in risk-management decision-making, by examining the effects of exposures to PCBs on fish populations inhabiting the Hudson River, New York, USA, a system in which data have been collected for approximately 30 y concerning both concentrations of PCBs in sediment and fish tissue and the abundance and reproduction of exposed fish populations. We previously tested hypotheses concerning the effects of PCBs on the striped bass population of the Hudson River, and found that the available data conflicted with all of these hypotheses. Here, we report results of similar analyses of effects of historic PCB exposures on the Hudson River white perch population, using an extended data set that recently became available. As with striped bass, we found no correlation between maternal PCB tissue concentrations and any measure of reproductive success in Hudson River white perch during the 30-y period covered by the data set. Together with results of studies performed on fish populations exposed to PCBs at other sites, our results clearly demonstrate that physiological and genetic adaptation, biological compensation, and other ecological processes influence responses of fish populations to PCB exposures and should be considered in risk management decision-making.

Quantifying population recovery rates for ecological risk assessment.

Ecological effects of modern agrochemicals are typically limited to brief episodes of increased mortality or reduced growth that are qualitatively similar to natural disturbance regimes. The long-term ecological consequences of agrochemical exposures depend on the intensity and frequency of the exposures relative to the rates of recovery of the exposed populations. This paper explores the feasibility of using readily available life history information to quantify recovery rates of aquatic populations. A simple modeling framework based on the logistic population growth model is used to compare population recovery rates for different types of organisms and to evaluate the influence of life history, initial percent reduction, disturbance frequency, and immigration on the time required for populations to recover from simulated agrochemical exposures. Recovery models are developed for aquatic biota ranging in size and longevity from unicellular algae to fish and turtles. Population growth rates and recovery times derived from life history data are consistent with measured recovery times reported in mesocosm and enclosure experiments, thus supporting the use of the models for quantifying population recovery rates for ecological risk assessment.

Effects of historic PCB exposures on the reproductive success of the Hudson River striped bass population.

Scientists and regulatory agencies have expressed concern that exposures to polychlorinated biphenyls (PCBs) might be contributing to reductions in the abundance of fish populations exposed to these chemicals. The specific effects of concern involve impairment of fish reproduction, including both reduced egg production and decreased viability of eggs and larvae. We tested hypotheses concerning the effects of PCBs on fish populations using long-term data sets available for the striped bass population of the Hudson River, NY, a population that has long been a subject of regulatory concern because of potential effects of PCB exposures. The data sets examined include both measurements of PCB concentrations in adult female striped bass over the period from 1976 through 1997 and estimates of the numbers of striped bass eggs, larvae, and juveniles produced annually during this same period. We found strong correlations between estimates of the abundance of spawners and the number of eggs and larvae produced by those spawners and also between independent estimates of year-class strength derived from different sampling programs. However, we found no relationships between PCB exposure and any measure of striped bass abundance or reproduction. Although inconsistent with the expected effects of PCB exposures, trends in all measures of striped bass abundance and reproductive success were consistent with the expected effects of striped bass harvest restrictions that were imposed during the 1980s. Our results demonstrate a need for caution in inferring risks to populations in nature from effects observed in laboratory studies.

Quantifying natural resource injuries and ecological service reductions: challenges and opportunities.

The natural resource damage assessment (NRDA) provisions of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and the Oil Pollution Act (OPA) are complex and have been difficult to implement. The complexity and difficulty in implementation arise both from the assessment procedures specified in agency NRDA guidance and from the limited ability of ecologists to quantify impacts of hazardous substances on natural resources. This paper explores the scientific aspects of NRDA implementation, and discusses conceptual and methodological relationships between NRDA and the much broader field of ecological risk assessment (ERA). We discuss three critical components of the NRDA assessment approach: measuring natural resource injuries and reductions in resource services; evaluating causality; and establishing baseline conditions. We identify (1) specific approaches drawn from ERA practice that could improve each of these components, and (2) research needs and institutional changes that may improve the ability of the NRDA process to achieve its stated objectives. We recommend the acceleration of the ongoing dialogue among NRDA practitioners from the Trustee and PRP communities as a first step toward resolving the procedural and technical deficiencies of the NRDA process.

Indicators of AEI applied to the Delaware Estuary.

We evaluated the impacts of entrainment and impingement at the Salem Generating Station on fish populations and communities in the Delaware Estuary. In the absence of an agreed-upon regulatory definition of "adverse environmental impact" (AEI), we developed three independent benchmarks of AEI based on observed or predicted changes that could threaten the sustainability of a population or the integrity of a community. Our benchmarks of AEI included: (1) disruption of the balanced indigenous community of fish in the vicinity of Salem (the "BIC" analysis); (2) a continued downward trend in the abundance of one or more susceptible fish species (the "Trends" analysis); and (3) occurrence of entrainment/impingement mortality sufficient, in combination with fishing mortality, to jeopardize the future sustainability of one or more populations (the "Stock Jeopardy" analysis). The BIC analysis utilized nearly 30 years of species presence/absence data collected in the immediate vicinity of Salem. The Trends analysis examined three independent data sets that document trends in the abundance of juvenile fish throughout the estuary over the past 20 years. The Stock Jeopardy analysis used two different assessment models to quantify potential long-term impacts of entrainment and impingement on susceptible fish populations. For one of these models, the compensatory capacities of the modeled species were quantified through meta-analysis of spawner-recruit data available for several hundred fish stocks. All three analyses indicated that the fish populations and communities of the Delaware Estuary are healthy and show no evidence of an adverse impact due to Salem. Although the specific models and analyses used at Salem are not applicable to every facility, we believe that a weight of evidence approach that evaluates multiple benchmarks of AEI using both retrospective and predictive methods is the best approach for assessing entrainment and impingement impacts at existing facilities.