Kate A. Schofield

Twenty-six key research questions in urban stream ecology: an assessment of the state of the science

Abstract Urban streams have been the focus of much research in recent years, but many questions about the mechanisms driving the urban stream syndrome remain unanswered. Identification of key research questions is an important step toward effective, efficient management of urban streams to meet societal goals. We developed a list of priority research questions by: 1) soliciting input from interested scientists via a listserv and online survey, 2) holding an open discussion on the questions at the Second Symposium on Urbanization and Stream Ecology, and 3) reviewing the literature in the preparation of this paper. We present the resulting list of 26 questions in the context of a review and summary of the present understanding of urban effects on streams. The key questions address major gaps in our understanding of ecosystem structure and function responses (e.g., what are the sublethal impacts of urbanization on biota?), characteristics of urban stream stressors (e.g., can we identify clusters of covarying stressors?), and management strategies (e.g., what are appropriate indicators of ecosystem structure and function to use as management targets?). The identified research needs highlight our limited understanding of mechanisms driving the urban stream syndrome and the variability in characteristics of the effects of urbanization across different biogeoclimatic conditions, stages of development, government policies, and cultural norms. We discuss how to proceed with appropriate management activities given our current incomplete understanding of the urban stream syndrome.Urban streams have been the focus of much research in recent years, but many questions about the mechanisms driving the urban stream syndrome remain unanswered. Identification of key research questions is an important step toward effective, efficient management of urban streams to meet societal goals. We developed a list of priority research questions by: 1) soliciting input from interested scientists via a listserv and online survey, 2) holding an open discussion on the questions at the Second Symposium on Urbanization and Stream Ecology, and 3) reviewing the literature in the preparation of this paper. We present the resulting list of 26 questions in the context of a review and summary of the present understanding of urban effects on streams. The key questions address major gaps in our understanding of ecosystem structure and function responses (e.g., what are the sublethal impacts of urbanization on biota?), characteristics of urban stream stressors (e.g., can we identify clusters of covarying stressors?), and management strategies (e.g., what are appropriate indicators of ecosystem structure and function to use as management targets?). The identified research needs highlight our limited understanding of mechanisms driving the urban stream syndrome and the variability in characteristics of the effects of urbanization across different biogeoclimatic conditions, stages of development, government policies, and cultural norms. We discuss how to proceed with appropriate management activities given our current incomplete understanding of the urban stream syndrome.

CADDIS: The Causal Analysis/Diagnosis Decision Information System

Biological monitoring and assessment methods have become indispensable tools for evaluating the condition of aquatic and terrestrial ecosystems. When an undesirable biological condition is observed (e.g., a depauperate fish assemblage), its cause (e.g., toxic substances, excess fine sediments, or nutrients) must be determined in order to design appropriate remedial management actions. Causal analysis challenges environmental scientists to bring together, analyze, and synthesize a broad variety of information from monitoring studies, models, and experiments to determine the probable cause of ecological effects. Decision-support systems can play an important role in improving the efficiency, quality and transparency of causal analyses.

Physical and Chemical Connectivity of Streams and Riparian Wetlands to Downstream Waters: A Synthesis

Streams, riparian areas, floodplains, alluvial aquifers and downstream waters (e.g., large rivers, lakes, oceans) are interconnected by longitudinal, lateral, and vertical fluxes of water, other materials and energy. Collectively, these interconnected waters are called fluvial hydrosystems. Physical and chemical connectivity within fluvial hydrosystems is created by the transport of nonliving materials (e.g., water, sediment, nutrients, contaminants) which either do or do not chemically change (chemical and physical connections, respectively). A substantial body of evidence unequivocally demonstrates physical and chemical connectivity between streams and riparian wetlands and downstream waters. Streams and riparian wetlands are structurally connected to downstream waters through the network of continuous channels and floodplain form that make these systems physically contiguous, and the very existence of these structures provides strong geomorphologic evidence for connectivity. Functional connections between streams and riparian wetlands and their downstream waters vary geographically and over time, based on proximity, relative size, environmental setting, material disparity, and intervening units. Because of the complexity and dynamic nature of connections among fluvial hydrosystem units, a complete accounting of the physical and chemical connections and their consequences to downstream waters should aggregate over multiple years to decades.

Biota connect aquatic habitats throughout freshwater ecosystem mosaics

Freshwater ecosystems are linked at various spatial and temporal scales by movements of biota adapted to life in water. We review the literature on movements of aquatic organisms that connect different types of freshwater habitats, focusing on linkages from streams and wetlands to downstream waters. Here, streams, wetlands, rivers, lakes, ponds, and other freshwater habitats are viewed as dynamic freshwater ecosystem mosaics (FEMs) that collectively provide the resources needed to sustain aquatic life. Based on existing evidence, it is clear that biotic linkages throughout FEMs have important consequences for biological integrity and biodiversity. All aquatic organisms move within and among FEM components, but differ in the mode, frequency, distance, and timing of their movements. These movements allow biota to recolonize habitats, avoid inbreeding, escape stressors, locate mates, and acquire resources. Cumulatively, these individual movements connect populations within and among FEMs and contribute to local and regional diversity, resilience to disturbance, and persistence of aquatic species in the face of environmental change. Thus, the biological connections established by movement of biota among streams, wetlands, and downstream waters are critical to the ecological integrity of these systems. Future research will help advance our understanding of the movements that link FEMs and their cumulative effects on downstream waters.

Weaving common threads in environmental causal assessment methods: toward an ideal method for rapid evidence synthesis*

Accurate and informative methods for evidence synthesis that are also simple and inexpensive to implement would greatly increase our ability to use scientific research results to better manage natural environments. Across the world, pressure to use evidence-based environmental management is increasing, but little guidance exists as to what ‘evidence-based’ actually means. Methods for systematic review of literature evidence have been modified from those used in medical research, but the effort involved in using these methods means that they have not been widely adopted. We compared 3 independently developed approaches to ‘rapid evidence synthesis’ methods developed in an attempt to improve efficiency and responsiveness compared to standard methods for systematic review. Each method has features that should be included in an ideal rapid evidence-synthesis method and has potential for further development. Increasing standardization of methods for evidence extraction, quality assessment, and synthesis increases the transparency and repeatability of the results obtained. However, the most important consideration is that the methods are fit for purpose; i.e., that each method is good enough to do the job required. The methods presented in this BRIDGES cluster, and potentially a combined method derived from them, could reduce the effort and cost of evidence synthesis to the scales required for management decisions.

Featured collection introduction: Connectivity of streams and wetlands to downstream waters

Connectivity is a fundamental but highly dynamic property of watersheds. Variability in the types and degrees of aquatic ecosystem connectivity presents challenges for researchers and managers seeking to accurately quantify its effects on critical hydrologic, biogeochemical, and biological processes. However, protecting natural gradients of connectivity is key to protecting the range of ecosystem services that aquatic ecosystems provide. In this featured collection, we review the available evidence on connections and functions by which streams and wetlands affect the integrity of downstream waters such as large rivers, lakes, reservoirs, and estuaries. The reviews in this collection focus on the types of waters whose protections under the U.S. Clean Water Act have been called into question by U.S. Supreme Court cases. We synthesize 40+ years of research on longitudinal, lateral, and vertical fluxes of energy, material, and biota between aquatic ecosystems included within the Act’s frame of reference. Many questions about the roles of streams and wetlands in sustaining downstream water integrity can be answered from currently available literature, and emerging research is rapidly closing data gaps with exciting new insights into aquatic connectivity and function at local, watershed, and regional scales. Synthesis of foundational and emerging research is needed to support science-based efforts to provide safe, reliable sources of fresh water for present and future generations. (KEY TERMS: ecological integrity; river networks; streams; wetlands; floodplains; riparian areas; watersheds; U.S. Clean Water Act.) Alexander, Laurie C., Ken M. Fritz, Kate A. Schofield, Bradley C. Autrey, Julie E. DeMeester, Heather E. Golden, David C. Goodrich, William G. Kepner, Hadas R. Kiperwas, Charles R. Lane, Stephen D. LeDuc, Scott G. Leibowitz, Michael G. McManus, Amina I. Pollard, Caroline E. Ridley, Melanie K. Vanderhoof, and Parker J. Wigington, Jr., 2018. Featured Collection Introduction: Connectivity of Streams and Wetlands to Downstream Waters. Journal of the American Water Resources Association (JAWRA) 54(2): 287–297. https://doi.org/10.1111/ 1752-1688.12630 Paper No. JAWRA-17-0107-P of the Journal of the American Water Resources Association (JAWRA). Received July 24, 2017; accepted January 22, 2018.

Timely delivery of scientific knowledge for environmental management: a Freshwater Science initiative

National Center for Environmental Assessment, Office of Research and Development, US Environmental Protection Agency, Washington, DC 20460 USA Department of Infrastructure Engineering, University of Melbourne, Parkville, Victoria 3010, Australia Centre for Evidence Informed Policy and Practice, Australia (https://ceipp.org.au/) Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, 2617 Australia Centre for Environmental Policy, Imperial College, London, SW7 1NA UK

Conceptual model diagrams as evidence scaffolds for environmental assessment and management

Sound environmental management relies on scientific evidence to indicate whether action is warranted and, if so, which actions will be most effective. We discuss conceptual model diagrams that schematically describe how sources or human activities lead to specific stressors and ultimately to biotic effects. They are useful for describing how undesirable effects are produced and identifying where management actions may be most effective in preventing unwanted effects or improving existing conditions. We illustrate the use of conceptual model diagrams in a literature-based assessment of the impacts of mountaintop removal mining on downstream aquatic systems. The diagram-development process combined extraction and evaluation of research results with iterative refinement of diagrams depicting source-to-stressor-to-effect causal pathways. Conceptual-model diagrams provided a useful scaffold for organizing and synthesizing multiple individual pieces of evidence extracted from different studies and an effective way to summarize and present the evidentiary foundation of the assessment’s conclusions.

Response of chlorophyll a to total nitrogen and total phosphorus concentrations in lotic ecosystems: a systematic review protocol

BackgroundEutrophication 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?”MethodsSearches 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.

Differing Modes of Biotic Connectivity within Freshwater Ecosystem Mosaics

Abstract We describe a collection of aquatic and wetland habitats in an inland landscape, and their occurrence within a terrestrial matrix, as a “freshwater ecosystem mosaic” (FEM). Aquatic and wetland habitats in any FEM can vary widely, from permanently ponded lakes, to ephemerally ponded wetlands, to groundwater‐fed springs, to flowing rivers and streams. The terrestrial matrix can also vary, including in its influence on flows of energy, materials, and organisms among ecosystems. Biota occurring in a specific region are adapted to the unique opportunities and challenges presented by spatial and temporal patterns of habitat types inherent to each FEM. To persist in any given landscape, most species move to recolonize habitats and maintain mixtures of genetic materials. Species also connect habitats through time if they possess needed morphological, physiological, or behavioral traits to persist in a habitat through periods of unfavorable environmental conditions. By examining key spatial and temporal patterns underlying FEMs, and species‐specific adaptations to these patterns, a better understanding of the structural and functional connectivity of a landscape can be obtained. Fully including aquatic, wetland, and terrestrial habitats in FEMs facilitates adoption of the next generation of individual‐based models that integrate the principles of population, community, and ecosystem ecology.