Stream Ecology Structure and Function of Running Waters

Stream

Ecology

Stream

Ecology

Structure and

function of

running waters

Second Edition

J. David Allan

School of Natural Resources & Environment,

The University of Michigan,

Ann Arbor, MI, U.S.A.

MarI¤aM. Castillo

Departamento de Estudios Ambientales,

Universidad Simo¤n BolI¤var,

Caracas,Venezuela

A C.I.P. Catalogue record for this book is available from the Library of Congress.

ISBN 978-1-4020-5583-6 (e-book)

Published by Springer,

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Printed on acid-free paper

The cover photograph shows the Autana River, a blackwater river in the Orinoco basin

of Venezuela. In the background is the Autana Mountain, sacred to the Piaroa people,

whose culture and livelihood are closely connected to the river. Photograph by M M Castillo

All Rights Reserved

2007 Springer

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Dedicated to our families, with gratitude for their support

Contents

Preface to the Second Edition xiii

1 An introduction to fluvial ecosystems 1

Fluvial Ecosystem Diversity 1

The fluvial hierarchy 2

Longitudinal patterns 5

The stream and its valley 5

The Fluvial Ecosystem 6

Energy sources 6

Food webs and biological communities 7

The river ecosystem 8

The Status of Rivers Today 9

2 Streamflow 13

The Water Cycle 14

Global water cycle 16

Water balance of a catchment 16

Surface versus groundwater pathways 18

Streamflow 19

The hydrograph 21

Flow Variation 22

The likelihood of extreme events 23

Effect of land use on streamflow 24

The flow regime 25

Environmental flows 30

Summary 31

3 Fluvial geomorphology 33

The Drainage Network 34

The Stream Channel 35

Hydraulic geometry 36

Sinuosity 38

Pool–riffle features 39

The floodplain 41

Sediments and their Transport 41

vii

Bed material 41

Bank and bed erosion 43

Sediment load 44

Factors influencing sediment concentrations and loads 46

Fluvial Processes along the River Continuum 49

Fluvial processes and channel morphologies 50

Channel dynamics over long timeframes 53

Channel classifications and their uses 53

Riverine landscape diversity 55

Summary 55

4 Streamwater chemistry 57

Dissolved Gases 57

Major Dissolved Constituents of River Water 59

Variability in ionic concentrations 62

The dissolved load 64

Chemical classification of river water 65

The Bicarbonate Buffer System 65

Influence of Chemical Factors on the Biota 68

Variation in ionic concentration 68

Salinization 69

Effects of acidity on stream ecosystems 70

Summary 74

5 The abiotic environment 75

The Flow Environment 76

Channel and near-bed flow environments 79

Hydraulic variables 79

Quantification of flow conditions 81

Influence of flow on the biota 82

Substrate 88

Inorganic substrates 89

Organic substrates 90

The influence of substrate on stream assemblages 92

Temperature 94

Influence of thermal regime on the biota 98

Summary 102

6 Primary producers 105

Benthic Algae 105

Benthic algal distribution and abundance 107

Light 109

Nutrients 112

Current 115

Substrate 120

Contents

viii

Temperature 120

Grazers 120

Temporal and spatial variation in benthic algae 121

Primary production by benthic algae 122

Fate of benthic primary production 124

Macrophytes 125

Limiting factors for macrophytes 126

Macrophyte production and its fate 128

Phytoplankton 129

Limiting factors for phytoplankton 130

Primary production by river phytoplankton 132

Summary 133

7 Detrital energy sources 135

The Decomposition of Coarse Particulate Organic Matter 135

Stages in the breakdown and decay of CPOM 139

The influence of detritivores on litter decomposition 144

Other CPOM 146

Fine Particulate Organic Matter 147

FPOM originating from leaf decomposition 148

Other sources of FPOM 149

Dissolved Organic Matter 150

Uptake of DOC 152

Biofilms 154

Bacterioplankton 158

Summary 160

8 Trophic relationships 163

Microbial Food Webs 164

Invertebrate Feeding Roles 167

Consumers of CPOM 168

Consumers of FPOM 173

Herbivory 177

Predaceous invertebrates 180

Vertebrates in Lotic Food Webs 183

Fishes 184

Other vertebrates 188

Secondary Production 190

Summary 195

9 Species interactions 197

Herbivory 197

Grazer responses to food supply 197

Grazer effects on periphyton 199

Structural responses 200

Contents

ix

Functional responses 202

Disturbance and herbivory 203

Top-down and bottom-up effects on periphyton 204

Predation 205

The predator–prey interaction 206

Vertebrate predators 206

Invertebrate predators 207

Prey defenses 209

Effects of predation on prey populations 210

Nonconsumptive effects of predation 211

Experimental scale 213

Trophic cascades 214

Competition 217

Resource partitioning 217

Algae 217

Invertebrates 218

Fishes 219

Experimental studies of competition 222

Summary 225

10 Lotic communities 229

Regional Patterns in Species Diversity 230

Species–area relationships 230

Latitudinal gradients 231

History 231

Local Diversity 233

Community Structure 238

Consistency in assemblage composition 239

The habitat template and species traits 240

Disturbance 242

Species-level effects of disturbance 244

System-wide effects 245

Food Webs 246

Resource subsidies 249

Landscape position 250

Community Composition and Ecosystem Function 251

Summary 253

11 Nutrient dynamics 255

Sources and Cycling of Nitrogen and Phosphorus 256

Nitrogen sources and quantities 257

Nitrogen cycling 259

Phosphorus sources and quantities 261

Phosphorus cycling 264

Transport and Spiraling 265

Contents

x

Physical transport 265

Nutrient spiraling 267

Methodological issues 268

Factors Influencing Nutrient Dynamics 269

Abiotic controls of nutrient dynamics 269

Hydrologic processes 270

Biotic controls of nutrient cycling 272

Assimilatory uptake 273

Dissimilatory transformations 275

Role of consumers 277

Nutrient Budgets 279

Nitrogen 280

Phosphorus 283

Summary 284

12 Stream ecosystem metabolism 287

Autochthonous Production 289

Algae 289

Macrophytes 290

Allochthonous Inputs 291

Coarse particulate organic matter 291

Fine particulate organic matter 292

Dissolved organic matter 294

Processes 297

Benthic respiration 297

Coarse particulate organic matter dynamics 298

Fine particulate organic matter dynamics 299

Benthic organic matter retention 300

Dissolved organic matter dynamics 302

Stream Ecosystem Metabolism 303

Organic matter budgets 303

The P/R ratio 308

Stream ecosystem efficiency 313

The fate of organic matter 314

Summary 315

13 Human impacts 317

Freshwater Biodiversity 318

Species imperilment 319

Imperilment of major groups 320

Threats to Rivers 321

Habitat alteration 321

Altered hydrology 323

Channelization 327

Land use 330

Contents

xi

Nonindigenous species 333

Causes of species invasions 333

Invasion success 334

Impacts of invasive species 337

Pollution 339

Point source contaminants 339

Runoff from the land 339

Atmospheric deposition 341

Overexploitation 342

Climate change 345

River Management 347

Bioassessment 348

Restoration and recovery of lotic ecosystems 350

Protected areas 354

Summary 356

14 The foundations of stream ecology 359

The Spatial Framework 360

Community Assembly is Determined by the Species Pool,

Habitat Sorting, and Species Interactions 362

Streams are Transporting Systems 364

Primary Production and Allochthonous Detritus are Basal Resources

in Lotic Ecosystems 366

Rivers are the Product of their Landscapes 369

References 373

Subject Index 429

Contents

xii

Preface to

the Second

Edition

The diversity of running water environments is

enormous. When one considers torrential moun￾tain brooks, large rivers of lowlands, and great

rivers whose basins occupy subcontinents, it is

apparent how location-specific environmental

factors contribute to the sense of uniqueness

and diversity of running waters. At the same

time, however, our improved understanding of

ecological, biogeochemical, hydrological, and

geomorphological processes provides insight

into the structural and functional characteristics

of river systems that brings a unifying framework

to this field of study. Inputs and transformations

of energy and materials are important in all river

systems, regional species richness and local spe￾cies interactions influence the structure of all

riverine communities, and the interaction of phy￾sical and biological forces is important to virtual￾ly every question that has been asked. It seems

that the processes acting in running waters are

general, but the settings are often unique.

We believe that it helps the reader, when some

pattern or result is described, to have some

image of what kind of stream or river is under

investigation, and also where it is located.

Stream ecology, like all ecology, depends greatly

on context: place, environmental conditions,

season, and species. This text includes frequent

use of descriptors like ‘‘small woodland stream,’’

‘‘open pastureland stream,’’ or ‘‘large lowland

river,’’ and we believe that readers will find

these useful clues to the patterns and processes

that are reported. For most studies within the

United States we have included further regional

description, but have done so less frequently for

studies from elsewhere around the globe. We

apologize to our international readers for this

pragmatic choice, and we have made every

effort to include examples and literature from

outside of North America.

Some locations have established themselves as

leading centers of study due to the work of many

researchers carried out over decades. The Hub￾bard Brook Experimental Forest in New Hamp￾shire, Coweeta Hydrologic Laboratory in North

Carolina, and some individual streams including

Walker Branch in Tennessee, Sycamore Creek in

Arizona, Rı´o las Marı´as in Venezuela, and the

Taeri and Whatawhata in New Zealand are loca￾tions that appear frequently in the pages that

follow. Knowing what these places are like, and

how they may or may not be typical, in our view

justifies the frequent use of place names and

brief descriptions. The names of organisms also

appear frequently and may at first overwhelm

the reader. It may be easiest to pay them little

attention until they gradually become familiar.

Ultimately, it is difficult to really comprehend

the outcome of a study without some apprecia￾tion for the organisms that were present.

xiii

As is true for every area of ecology at present,

the study of streams and rivers cannot be

addressed exclusive of the role of human activ￾ities, nor can we ignore the urgency of the need

for conservation. This is a two-way street. Ecol￾ogists who study streams without considering

how past or present human modifications of

the stream or its valley might have contributed

to their observations do so at the risk of incom￾plete understanding. Conservation efforts that

lack an adequate scientific basis are less likely

to succeed. One trend that seems safe to forecast

in stream ecology is toward a greater emphasis

on understanding human impacts. Fortunately,

signs of this trend are already apparent.

We have organized the flow of topics in a way

that is most logical to us, but no doubt some

readers will prefer to cover topics in whatever

order they find most useful. For this reason, we

have striven to explain enough in each chapter so

that it is comprehensible on its own. This leads to

a certain amount of intentional repetition, which

we hope will provide clarification or a reminder

that will benefit the reader’s understanding.

We are extremely grateful to the many collea￾gues who shared ideas, provided references, and

reviewed chapters in draft form. Space does not

permit us to thank everyone who answered a

query with a helpful explanation and sugges￾tions for source material; however, we do wish

to acknowledge the persons who carefully read

and improved our chapters. Any remaining short￾comings or errors are the authors’ responsibility,

but hopefully these are few, thanks to the efforts

of Robin Abell, Brian Allan, Fred Benfield, Barb

Downes, David Dudgeon, Kurt Fausch, Stuart

Findlay, Alex Flecker, Art Gold, Sujay Kaushal,

Matt Kondolf, Angus McIntosh, Peter McIntyre,

Rich Merritt, Judy Meyer, Pat Mulholland, Bobbi

Peckarsky, LeRoy Poff, Brian Roberts, Doug

Shields, Al Steinman, Jan Stevenson, Jen Tank,

Paul Webb, Jack Webster, Kevin Wehrly, and Kirk

Winemiller. All were generous with their time

and knowledge, and we are indebted to them.

We also wish to thank those who provided

helpful reviews of chapters in the first edition of

this book, including Fred Benfield, Art Benke, Art

Brown, Scott Cooper, Stuart Findlay, Alex Flecker,

Nancy Grimm, David Hart, Chuck Hawkins, Bob

Hughes, Steve Kohler, Gary Lamberti, Rex Lowe,

Rich Merritt, Diane McKnight, Judy Meyer, Bobbi

Peckarsky, Pete Ode, Walt Osterkamp, ML

Ostrofsky, Margaret Palmer, LeRoy Poff, Karen

Prestergaard, Ike Schlosser, Len Smock, Al Stein￾man, Scott Wissinger, and Jack Webster.

Others provided invaluable assistance with

important aspects of manuscript production.

Jennifer Allan, Mary Hejna and Jamie Steffes did

extensive proofreading and arranged all the fig￾ure permissions. Haymara Alvarez, Susana Marti￾nez, and Dana Infante assisted with production

of figures, and Jesus Montoya did a superb job of

taking figures made in many different styles and

redrafting them to a common style and high

quality. Funding for MMC release time and travel

to Michigan was provided by Direccio´n de

Desarrollo Profesoral of Universidad Simo´n

Bolı´var, and the Horace H. Rackham School of

Graduate Studies of the University of Michigan.

We also wish to thank our editors at Springer,

Suzanne Mekking and Martine van Bezooijen,

and our prior editor Anna Besse-Lototskaya, for

their support, encouragement, and patience. It

has been a pleasure to work with them all.

Lastly, our deepest thanks go to our families

for their love and support, and especially for

their help and understanding during the time

this edition was completed. David wishes to

express his appreciation to Susan for the unflag￾ging encouragement that has been a constant

throughout our lives together. Marı´a Mercedes

wishes to thank her parents for their uncondi￾tional support in the development of her career.

It has been an enjoyable experience for both of

us, and we hope that this edition will serve as a

useful guide for the next generation of stream

ecologists.

xiv

Preface to the Second Edition

Chapter one

An

introduction

to fluvial

ecosystems

This chapter provides an overview of the diver￾sity of rivers and streams, including some of the

causes of this diversity, and some of the conse￾quences. The intent is to provide a road map for

the individual chapters that follow, rather than

define terms and explain principles in detail. By

sketching out the broadest patterns of fluvial

ecosystems and providing at least a glimpse of

the underlying processes, we hope this introduc￾tion will serve as a framework for the entire

book. Some of these generalizations may later

be qualified to recognize their exceptions and

limitations. Yet, it is through this effort to eluci￾date the working principles of fluvial ecosystems

and how environmental context governs their

expression that river ecologists hope to compre￾hend the enormous variety of streams and rivers,

and provide the needed guidance to ensure their

sustained well-being.

1.1 Fluvial Ecosystem Diversity

Streams and rivers occur in almost bewildering

variety. There is no real distinction between

streams and rivers, except that the former are

smaller. Some use the term ‘‘great river’’ to dis￾tinguish rivers such as the Mekong, the Amazon,

and the Mississippi from rivers of more usual

size. Partly because the vast majority of river

length is in the smaller headwater streams, and

partly because these smaller systems have

received considerably more study, many and

perhaps most researchers consider themselves

‘‘stream ecologists.’’ Attempting to understand

how the principles of fluvial systems are mani￾fested across scale is one of the primary themes

of this book.

Fluvial ecosystems vary in many additional

features. Some have the color of tea due to

high concentrations of dissolved plant matter,

while others have fewer chemical constituents

and so remain clear; these are known as black￾water and clearwater rivers, respectively. Rivers

can tumble and cascade down steep slopes over

large boulders, meander through gentle valleys,

or flow majestically across broad flats as they

approach the sea. Food webs in forested streams

derive much of their food base from autumn leaf

fall, whereas streams that are open, shallow, and

stony typically develop a rich film of algae and

microbes. Rivers that still have an intact flood￾plain exchange organic matter and nutrients

1

with the adjacent land, and all fluvial ecosystems

exhibit high connectivity laterally, longitudinally,

and vertically (Figure 1.1).

River science attempts to catalog this diversi￾ty, reveal the underlying processes that are re￾sponsible for the variety of patterns that we

observe, and understand how those processes

interact with different environmental settings

and across scale from the smallest headwater

streams to great rivers. Numerous classification

systems for rivers have been developed to better

comprehend natural patterns of variation, as

well as guide management activities including

restoration and assessments of river health. At

the time of this writing it is not possible to

describe one, overarching river classification. In￾deed, this may not be an attainable goal: the

variation of fluvial ecosystems is continuous,

the variables often are too independent to form

recognizable clusters, and different classifica￾tions have different purposes (Kondolf et al.

2003a, b). With these limitations in mind, how￾ever, a number of broad generalizations can be

made that help to organize the variety and varia￾bility of fluvial ecosystems.

1.1.1 Thefluvialhierarchy

Streams and the landscape units they drain form

nested hierarchies. The smallest permanently

flowing stream is referred to as first order. The

union of two first-order streams results in a sec￾ond-order stream, the union of two streams of

second order results in a third-order stream, and

so on (Figure 1.2). Stream order is an approxi￾mate measure of stream size, conceptually attrac￾tive, and correlates with a number of other, more

precise size measures including the area drained,

volume of water discharged, and channel dimen￾sions. As a simple classification system it pro￾vides an informative tally of the numbers of

small streams and large rivers (Table 1.1). The

great majority of the total length of river systems

is comprised of lower-order or headwater sys￾tems, each of short length and small drainage

area. Rivers that we might consider to be of

medium size, fourth through sixth order, are

FIGURE 1.1 The fluvial ecosystem with its three major

axes: upstream/downstream, channel/margins, and sur￾ficial/underground environments. (Reproduced from

Pie´gay and Schumm 2003.)

FIGURE 1.2 A drainage network illustrating stream chan￾nel order within a fourth-order catchment. The terminus

may be a lake or the junction with a larger river. Inter￾mittent streams occur upstream of the first-order tribu￾taries, and often extend nearly to the catchment divide.

An introduction to fluvial ecosystems

2