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Urbanization of watersheds leads to myriad changes to streams, including modified sediment and streamflow regimes that can result in altered fluvial geomorphic processes and channel structure. Hydrogeomorphic features have been linked to community composition of aquatic biota, as well as to stream ecosystem functioning. Biotic communities in urban stream ecosystems can be markedly different than their counterparts in more natural streams, often exhibiting reduced abundance, diversity, and shifts in assemblage composition, though the specific mechanisms through which urban land use and subsequent hydrogeomorphic modification effects these changes remain unresolved. Hydrogeomorphic modifications may impact both instream habitat as well as connectivity to the surrounding landscape, influencing both biotic assemblage composition as well as ecological connectivity between streams and their adjacent riparian zones. In 23 small urban stream reaches in the Columbus Metropolitan Area (CMA), Ohio, USA, I investigated potential linkages between urban-induced hydrogeomorphic characteristics and: (1) fish assemblage compositional changes over time (3-5 years); (2) fish assemblage trophic dynamics; (3) aquatic-to-terrestrial nutritional subsidies to a common riparian consumer (spiders of the family Tetragnathidae); and (4) downstream drift of larval macroinvertebrates in the water column. Hydrogeomorphic features related to instream habitat, the hydraulic environment (e.g., slope, shear stress, D50 [median bed sediment particle size]) and stream-floodplain connectivity (e.g., entrenchment ratio, sinuosity, incision ratio) emerged as common influences on fish assemblage composition and trophic dynamics, aquatic-terrestrial connectivity, and invertebrate drift. At a subset of 12 study reaches, several hydrogeomorphic variables showed significant changes over 3-5 years, with many decreasing (e.g., discharge [by 39%], slope [by 0.1%], and shear stress [by 29%, which decreased in concert with slope]). Fish assemblage evenness decreased over the study period in study reaches with higher incision ratio (t = 2.16, p = 0.039), accompanied by species-specific relationships with hydrogeomorphic characteristics. These findings explicitly link hydrogeomorphic and fish-community changes over time, showing that fluvial geomorphic forms in urban streams are not static, and can exert effects on fish assemblages over relatively short time periods, likely via shifts in instream habitat. In a wider suite of 23 study reaches, hydrogeomorphic characteristics – including slope and bankfull discharge – influenced fish-assemblage diversity (H’), density, and proportion of generalist foragers. Mean reliance on aquatically-derived energy (i.e., reliance on energy pathways derived from benthic algae) of Creek Chub (Semolitus atromaculatus) was 0.60, which increased with slope (Z = 2.27, p = 0.023), suggesting that channel gradient, a measure highly associated with shear stress, may moderate the relative abundance of autochthonous vs. allochthonous basal resources consumed by stream fish. Sunfish species (Lepomis cyanellus and L. macrochirus) relied on aquatically-derived energy for 0.62 of their nutrition, which was positively related to discharge (Z = 1.98, p = 0.048), suggesting an underlying mechanism of discharge-mediated bed disturbance as a control of basal resource availability. Hydrogeomorphic variables did not influence mean trophic position or food-chain length (FCL; ranging from 1.83-4.69 across all study reaches), which was more closely related to water nutrient concentrations (i.e., total N). Tetragnathid spider trophic position (x ̅ = 2.41) was negatively influenced by D50, while tetragnathid reliance on aquatically-derived energy (x ̅ = 0.43) trended positively with sinuosity (t = 2.10, p = 0.054), suggesting that tetragnathid spider trophic position is influenced by the impact of instream habitat on emergent aquatic insects, while aquatically-derived energy was more closely related to stream-floodplain connectivity. Tetragnathid density decreased with slope (t = -2.51, p = 0.023), as did the flux of emergent aquatic insects into the riparian zone (t = -2.27, p = 0.037). The relative abundance of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa in emergent aquatic insect assemblages was positively associated with sinuosity (t = 6.84, p
The Clean Water Act (CWA) requires that wetlands be protected from degradation because of their important ecological functions including maintenance of high water quality and provision of fish and wildlife habitat. However, this protection generally does not encompass riparian areasâ€"the lands bordering rivers and lakesâ€"even though they often provide the same functions as wetlands. Growing recognition of the similarities in wetland and riparian area functioning and the differences in their legal protection led the NRC in 1999 to undertake a study of riparian areas, which has culminated in Riparian Areas: Functioning and Strategies for Management. The report is intended to heighten awareness of riparian areas commensurate with their ecological and societal values. The primary conclusion is that, because riparian areas perform a disproportionate number of biological and physical functions on a unit area basis, restoration of riparian functions along America's waterbodies should be a national goal.
Multiple Stressors in River Ecosystems: Status, Impacts and Prospects for the Future provides a comprehensive and current overview on the topic as written by leading river scientists who discuss the relevance of co-occurring stressors for river ecosystems. River ecosystems are subject to multiple stressors that threaten their ecological status and the ecosystem services they provide. This book updates the reader’s knowledge on the response and management of river ecosystems to multi-stress situations occurring under global change. Detailing the risk for biodiversity and functioning in a case-study approach, it provides insight into methodological issues, also including the socioeconomic implications. Presents a case study approach and geographic description on the relevance of multiple stressors on river ecosystems in different biomes Gives a uniquely integrated perspective on different stressors, including their interactions and joint effects, as opposed to the traditional one-by-one approach Compiles state-of-the-art methods and technologies in monitoring, modeling and analyzing river ecosystems under multiple stress conditions
This book is developed from and includes the presentations of leading international experts and scholars in the 12-14 July, 2006 Wingspread Workshop. With urban waters as a focal point, this book will explore the links between urban water quality and hydrology, and the broader concepts of green cities and smart growth. It also addresses legal and social barriers to urban ecological sustainability and proposes practical ways to overcome those barriers. Cities of the Future features chapters containing visionary concepts on how to ensure that cities and their water resources become ecologically sustainable and are able to provide clean water for all beneficial uses. The book links North American and Worldwide experience and approaches. The book is primarily a professional reference aimed at a wide interdisciplinary audience, including universities, consultants, environmental advocacy groups and legal environmental professionals.
An ideal text for students taking a course in landscape ecology. The book has been written by very well-known practitioners and pioneers in the new field of ecological analysis. Landscape ecology has emerged during the past two decades as a new and exciting level of ecological study. Environmental problems such as global climate change, land use change, habitat fragmentation and loss of biodiversity have required ecologists to expand their traditional spatial and temporal scales and the widespread availability of remote imagery, geographic information systems, and desk top computing has permitted the development of spatially explicit analyses. In this new text book this new field of landscape ecology is given the first fully integrated treatment suitable for the student. Throughout, the theoretical developments, modeling approaches and results, and empirical data are merged together, so as not to introduce barriers to the synthesis of the various approaches that constitute an effective ecological synthesis. The book also emphasizes selected topic areas in which landscape ecology has made the most contributions to our understanding of ecological processes, as well as identifying areas where its contributions have been limited. Each chapter features questions for discussion as well as recommended reading.
Ecosystem research has emerged in recent decades as a vital, successful, and sometimes controversial approach to environmental science. This book emphasizes the idea that much of the progress in ecosystem research has been driven by the emergence of new environmental problems that could not be addressed by existing approaches. By focusing on successes and limitations of ecosystems studies, the book explores avenues for future ecosystem-level research.
"Wetlands" has become a hot word in the current environmental debate. But what does it signify? In 1991, proposed changes in the legal definities of wetlands stirred controversy and focused attention on the scientific and economic aspects of their management. This volume explores how to define wetlands. The committee--whose members were drawn from academia, government, business, and the environmental community--builds a rational, scientific basis for delineating wetlands in the landscape and offers recommendations for further action. Wetlands also discusses the diverse hydrological and ecological functions of wetlands, and makes recommendations concerning so-called controversial areas such as permafrost wetlands, riparian ecosystems, irregularly flooded sites, and agricultural wetlands. It presents criteria for identifying wetlands and explores the problems of applying those criteria when there are seasonal changes in water levels. This comprehensive and practical volume will be of interest to environmental scientists and advocates, hydrologists, policymakers, regulators, faculty, researchers, and students of environmental studies.