Quantitative Assessment of Drivers of Ecosystem Functions in Headwater Stream Networks
Quantitative Assessment of Drivers of Ecosystem Functions in Headwater Stream Networks

Author: Kaitlin Jean Farrell

Publisher:

Published: 2017

Total Pages: 348

ISBN-13:

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Effectively valuing the contribution of small headwater streams to the functioning of river networks requires an understanding of how physical and biological drivers are linked to ecosystem functions, and of how drivers and functions vary, both within and among stream networks. Despite a large body of work on individual 1st and 2nd order streams, fewer studies have examined patterns in structure or function across different sized streams within a network. Here, I combined field experiments and cross-biome syntheses to link stream structure and function through two focal lenses; the quantity and quality of basal resources, and the role of stream consumers. When developing quantitative relationships between drivers and rates of ecosystem respiration (ER), gross primary production (GPP), and ammonium (NH4) uptake, I found that within a headwater stream network, coarse and fine benthic organic matter standing stocks were positively correlated with ER, while light availability was a strong driver of GPP. Based on extrapolation to the stream network, small 1st and 2nd order streams are expected to play a substantial role in ER and NH4 uptake compared to larger streams. Across four distinct stream networks, benthic organic matter carbon to nitrogen and phosphorus ratios were lower in fine than course fractions. This higher relative nutrient content in fine benthic organic matter suggested that macroinvertebrates feeding on coarse and fine organic matter could be broadly macronutrient or carbon limited, respectively, with implications for in-stream resource cycling. Stream consumers had limited detectable effects on measured metrics of structure and function, both within and among headwater networks. Larval salamanders did not initiate top-down trophic cascades, but reduced stream NH4 uptake rates, potentially through nitrogen excretion. We also did not detect significant consumer effects across stream networks from five biomes, despite differences in consumer biomass and trophic position. However, across biomes, basal resources were strong drivers of both ER and GPP, which indicated that study networks were bottom-up, rather than top-down controlled. Collectively, these four studies highlight the importance of linking measurements of structure and function in headwater streams, to quantify their role in larger stream networks, and as such, advocate for their protection.

The Influence of Network Structure, Habitat Fragmentation, and Faunal Sources on Aquatic Communities in Headwater Streams
The Influence of Network Structure, Habitat Fragmentation, and Faunal Sources on Aquatic Communities in Headwater Streams

Author: Sean D. Sipple

Publisher:

Published: 2017

Total Pages: 213

ISBN-13:

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Headwater streams comprise the majority of the stream network, providing important ecological functions to the downstream network. Although we are beginning to understand how network structure may influence fish, our understanding of how it influences benthic macroinvertebrate dispersal and population connectivity is limited. We also know little about how these patterns and processes may be disrupted as a result of human-driven landscape change such as stream barriers to movement and creation of artificial habitats such as stormwater and farm ponds. In this study, I investigated the effect of stream network position, stream size, and local habitat on benthic macroinvertebrates, and determined to what degree road crossings and impoundments may be degrading benthic macroinvertebrate and fish communities in headwater streams. These mechanisms were explored using Maryland Department of Natural Resources, (MDNR) Maryland Biological Stream Survey (MBSS) benthic macroinvertebrate, fish, and environmental data from first-order streams in the Piedmont region of Maryland. Using an Information Theoretic Approach (ITA), models were developed based on the hypothesized relationships between benthic macroinvertebrate and fish community structure and several network and anthropogenic impact variables. Based on my results, aquatic community structure was dependent on local habitat conditions and stream network structure. Both assemblages responded negatively to roads, which may suggest an isolation effect. These results also suggest that impoundments are acting as sources for benthic macroinvertebrates and fish, including non-native species.

Intermittent Rivers and Ephemeral Streams
Intermittent Rivers and Ephemeral Streams

Author: Thibault Datry

Publisher: Academic Press

Published: 2017-07-11

Total Pages: 624

ISBN-13: 0128039043

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Intermittent Rivers and Ephemeral Streams: Ecology and Management takes an internationally broad approach, seeking to compare and contrast findings across multiple continents, climates, flow regimes, and land uses to provide a complete and integrated perspective on the ecology of these ecosystems. Coupled with this, users will find a discussion of management approaches applicable in different regions that are illustrated with relevant case studies. In a readable and technically accurate style, the book utilizes logically framed chapters authored by experts in the field, allowing managers and policymakers to readily grasp ecological concepts and their application to specific situations. - Provides up-to-date reviews of research findings and management strategies using international examples - Explores themes and parallels across diverse sub-disciplines in ecology and water resource management utilizing a multidisciplinary and integrative approach - Reveals the relevance of this scientific understanding to managers and policymakers

Patterns and Determinants of Macroinvertebrate Diversity in Headwater Stream Networks
Patterns and Determinants of Macroinvertebrate Diversity in Headwater Stream Networks

Author: Amber Clarke

Publisher:

Published: 2010

Total Pages:

ISBN-13:

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Headwater streams dominate stream channel length in catchments. They are important sources of water, sediment and biota for downstream reaches and critical sites for organic matter and nutrient processing. Aquatic biodiversity in headwater streams has been overlooked in comparison to higher-order rivers, and few studies have considered spatial biodiversity patterns in headwater streams, or streams in general. I reviewed studies of macroinvertebrate diversity in headwater streams and found equivocal evidence to support the view that headwater streams harbour high biodiversity. Headwater streams might still make an important contribution to [gamma] (regional) diversity at the landscape (catchment) scale by virtue of high [beta] (among-assemblage) diversity. I studied eight headwater streams from three forested, upland catchments along the Great Dividing Range, Victoria, Australia to test my hypothesis of high [beta] diversity and to understand the spatial patterns and determinants of macroinvertebrate diversity in headwater stream networks.Diversity partitioning showed that reaches each had high [alpha] (within-assemblage) diversity, while [beta] diversity made only a small contribution to [gamma] diversity at both the reach and catchment scales. [beta] diversity may have been lower than hypothesized due to relatively small distances between sites and high levels of dispersal among reaches and catchments in the study area. Contrary to other studies that have found environmental factors to be important for explaining variation in macroinvertebrate assemblage structure in headwater streams, I found a limited role for environmental factors structuring macroinvertebrate assemblages in the study area.In one year (2008), spatial factors (independent of environmental factors) were the dominant factor structuring macroinvertebrate assemblages. Therefore, metacommunity structure in the study area aligns most closely with the neutral/patch dynamic metacommunity model. This pattern of spatial structuring, coupled with low [beta] diversity, suggests that high neighbourhood dispersal might be the main factor structuring macroinvertebrate assemblages in the study area. Flow permanence had only a seasonal effect on macroinvertebrate diversity and so there is a temporal component to the spatial diversity patterns in this system.The explicit recognition of stream ecosystems as spatially structured networks has increased our understanding of ecological patterns and processes, and provided the impetus for this research. Recent advances in the study of networks, particularly in the fields of physics and network theory, offer an opportunity to considerably extend the current application of the network concept in stream ecology.Determining the relative contributions of [alpha] and [beta] diversity to [gamma] diversity, and the scale dependence of [alpha] and [beta] components, provides vital information for conservation planning because optimal reserve designs will differ depending on the relative contributions of [alpha] and [beta] diversity. My finding of high [alpha] and low [beta] diversity indicates that each stream in the study area can be considered to have low irreplaceability and the capacity to contribute a large portion of species to regional conservation targets.Information on spatial patterns of diversity is urgently required for systematic conservation planning for freshwater reserves if we are to halt the rapid decline in global freshwater biodiversity.

River Networks as Ecological Corridors
River Networks as Ecological Corridors

Author: Andrea Rinaldo

Publisher: Cambridge University Press

Published: 2020-10-22

Total Pages: 457

ISBN-13: 1108477828

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A summary of state-of-the-art research on how the river environment impacts biodiversity, species invasions, population dynamics, and the spread of waterborne disease. Blending laboratory, field and theoretical studies, it is the go-to reference for graduate students and researchers in river ecology, hydrology, and epidemiology.

Microbial Diversity and Ecosystem Functioning in Fragmented Rivers Worldwide
Microbial Diversity and Ecosystem Functioning in Fragmented Rivers Worldwide

Author: Lunhui Lu

Publisher: Frontiers Media SA

Published: 2023-11-27

Total Pages: 188

ISBN-13: 2832539874

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Dams or barriers are among the most significant anthropogenic threats to global freshwater ecosystems, although they provide invaluable services for shipping, hydropower generation, flood protection, and storage of drinking and irrigation water. River fragmentations due to dams and barriers lead the aquatic landscape into isolated river sections, resulting in hydromorphological discontinuities along longitudinal or lateral gradients. Fragmented river habitats are unstable. They experience uncertain disturbances in both time and space with random and complex hydrological and environmental processes, such as water flow, particulate matter sedimentation, reservoir regulation, and terrestrial input. The diversity, composition, functionality, and activity of microbial communities are important indicators of river ecosystem functions and services. Yet, river fragmentations are likely to disrupt and reconstruct microbial communities, redirecting the patterns of biogeochemical cycles of biogenic elements. Methodology, such as mathematical models, is still limited to describing and elucidating microbial processes under changing hydrological environments in the fragmented rivers. Thus, how do the riverine microbial communities and ecosystem functions respond to the fragmentation in rivers? This Research Topic represents a collective focus on microbial ecology, functional diversity, and new microbial modeling in fragmented rivers. We wish to present new findings in community assembly mechanisms, biotic interactions, functional diversity, and ecosystem functioning responses to the river fragmentations. New perspectives will also provide us with deep insights into the ecological effects of river fragmentation. This Research Topic aims to present the original research articles and reviews to provide new findings on microbial diversity and ecosystem functioning in fragmented rivers worldwide. We welcome original research, reviews, mini-reviews, opinions, methods, hypotheses and theories, and perspectives. The directions include but are not limited to the following aspects: - The continuum of the microbial community in responses to dams or barriers. - Novel microbial community assembly mechanisms, functional traits, and biotic interactions in fragmented rivers at local, regional, and global scales. - Functional genes, functional groups, and functional diversity in driving biogenic element cycles. - Mathematical modeling in aquatic microbial ecology.

An Integrated Approach to Gauge the Effects of Global Climate Change on Headwater Stream Ecosystems
An Integrated Approach to Gauge the Effects of Global Climate Change on Headwater Stream Ecosystems

Author: Gwendolynn Wolfheim Bury

Publisher:

Published: 2015

Total Pages: 208

ISBN-13:

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Climate change is predicted to affect ecosystems, including systems already stressed by human impacts. One ecosystem that is already highly impacted by human land use is the cold headwater stream system of the Pacific Northwest. One method of assessing the function of an ecosystem is by using an indicator species. Rhyacotriton variegatus is one such indicator species, sensitive to disturbance, and especially to temperature elevation. This study combines field measurements from the warmest edge of the range of R. variegatus, laboratory determination of thermal tolerance, and modeling. These diverse experimental sources combine to clarify the potential risks of climate change on R. variegatus, and the headwater streams they occupy. Abiotic factors are important determinates of the range of species. Predicted range shifts under climate change are based on the assumption that temperature increases will make habitat at the edge of the known range unsuitable in the future. In order to accurately predict such changes, a quantification of the current thermal boundary is needed. In Chapter Two, I placed temperature loggers and measured other environmental variables in 28 streams: 8 in the cool core of the range of R. variegatus, 10 as far east and south as R. variegatus has ever been found, and 10 outside the known range of R. variegatus. The variables which best defined the range edge were degree days (number of days over specific temperatures), and the slope of the stream bed. Specific physiological tolerance information is also essential for accurate modeling of species habitats. Physiological limits should be determined experimentally using procedures that mimic natural conditions as closely as possible, so that the results will be applicable to natural systems. Forecasting the effects of human activities on populations also requires an understanding of how specific abiotic changes will impact different life stages. I used a realistic cycling temperature treatment in Capters Three and Four, based on the data collected in Chapter One. I tested the survival of larval R. variegatus at a chronic exposure (21 days), and the level of stress as measured by corticosterone in adult R. variegatus. Larval R. variegatus survived up to a daily maximum of 23° C, beyond this the larvae died (LT 50 value of 24° C). I found that daily maximum temperatures over 18° C caused a doubling of corticosterone. There are many ways of modeling future climate change and the effect of this change on species' distribution. I chose to use large array of potential climate futures, modeling methods, and time periods to forecast the change in R. variegatus' range. This allowed me to compare the variation between the predictions for climate change, and find averages across the models. I used two correlative models, and one mechanistic model. The mechanistic model incorporated the relationship between air and water temperature from Chapter Two, and the physiological limits from Chapters Three and Four. All models predicted decreases in areas of the map classified as excellent habitat for R. variegatus. As expected, the reduction in range was most severe at longer time periods into the future, with higher CO2 amounts in the atmosphere, and in models that incorporated more abiotic variables. R. variegatus are sensitive indicators for headwater stream ecosystem function, and will have a reduced range under climate change.

Drought and Aquatic Ecosystems
Drought and Aquatic Ecosystems

Author: P. Sam Lake

Publisher: John Wiley & Sons

Published: 2011-06-09

Total Pages: 458

ISBN-13: 1444341790

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Droughts are a major hazard to both natural and human-dominated environments and those, especially of long duration and high intensity, can be highly damaging and leave long-lasting effects. This book describes the climatic conditions that give rise to droughts, and their various forms and chief attributes. Past droughts are described including those that had severe impacts on human societies. As a disturbance, droughts can be thought of as “ramps” in that they usually build slowly and take time to become evident. As precipitation is reduced, flows from catchments into aquatic systems decline. As water declines in water bodies, ecological processes are changed and the biota can be drastically reduced, though species and populations may survive by using refuges. Recovery from drought varies in both rates and in degrees of completeness and may be a function of both refuge availability and connectivity. For the first time, this book reviews the available rather scattered literature on the impacts of drought on the flora, fauna and ecological processes of aquatic ecosystems ranging from small ponds to lakes and from streams to estuaries. The effects of drought on the biota of standing waters and flowing waters and of temporary waters and perennial systems are described and compared. In addition, the ways in which human activity can exacerbate droughts are outlined. In many parts of the world especially in the mid latitudes, global warming may result in increases in the duration and intensity of droughts. Drought and Aquatic Ecosystems is essential reading for freshwater ecologists, water resource managers and advanced students.

Ecohydrological Interfaces
Ecohydrological Interfaces

Author: Stefan Krause

Publisher: John Wiley & Sons

Published: 2023-10-12

Total Pages: 437

ISBN-13: 1119489660

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Ecohydrological Interfaces Comprehensive overview of the process dynamics and interactions governing ecohydrological interfaces Summarizing the interdisciplinary investigation of ecohydrological interface functioning, Ecohydrological Interfaces advances the understanding of their dynamics across traditional subject boundaries. It offers a detailed explanation of the underlying mechanisms and process interactions governing ecohydrological interface functioning from the micro scale to the ecosystem and regional scale. The multidisciplinary team of authors integrates and synthesises the current understanding of process dynamics at different ecohydrological interfaces to develop a unifying concept of their ecosystem functions. The work introduces novel experimental and model-based methods for characterizing and quantifying ecohydrological interface processes, taking account of innovative sensing and tracing technologies as well as microbial and molecular biology approaches. Key questions addressed in the book include: Which conditions stimulate the transformative nature of ecohydrological interfaces? How are ecohydrological interfaces organized in space and time? How does interface activity propagate from small to large scales? How do ecohydrological interfaces react to environmental change and what is their role in processes of significant societal value? As a research level text on the functionality and performance of ecohydrological interfaces, Ecohydrological Interfaces is primarily aimed at academics and postgraduate researchers. It is also appropriate for university libraries as further reading on a range of geographical, environmental, biological, and engineering topics.

River Science
River Science

Author: David J. Gilvear

Publisher: John Wiley & Sons

Published: 2016-05-02

Total Pages: 430

ISBN-13: 1119994349

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River Science is a rapidly developing interdisciplinary field at the interface of the natural sciences, engineering and socio-political sciences. It recognises that the sustainable management of contemporary rivers will increasingly require new ways of characterising them to enable engagement with the diverse range of stakeholders. This volume represents the outcome of research by many of the authors and their colleagues over the last 40 years and demonstrates the integral role that River Science now plays in underpinning our understanding of the functioning of natural ecosystems, and how societal demands and historic changes have affected these systems. The book will inform academics, policy makers and society in general of the benefits of healthy functioning riverine systems, and will increase awareness of the wide range of ecosystem goods and services they provide.