Ecology and Classification of North American Freshwater Invertebrates (eBook)

Alan P. Covich, James H. Thorp (Herausgeber)

eBook Download: EPUB

2001 | 2. Auflage
1056 Seiten
Elsevier Science (Verlag)
978-0-08-053067-3 (ISBN)

Infos

The First Edition of Ecology and Classification of North American Freshwater Invertebrates has been immensely popular with students and researchers interested in freshwater biology and ecology, limnology, environmental science, invertebrate zoology, and related fields. The First Edition has been widely used as a textbook and this Second Edition should continue to serve students in advanced classes. The Second Edition features expanded and updated chapters, especially with respect to the cited references and the classification of North American freshwater invertebrates. New chapters or substantially revised chapters include those on freshwater ecosystems, snails, aquatic spiders, aquatic insects, and crustaceans.

* Most up-to-date and informative text of its kind
* Written by experts in the ecology of various invertebrate groups, coverage emphasizes ecological information within a current taxonomic framework
* Each chapter contains both morphological and taxonomic information, including keys to North American taxa (usually to the generic level) as well as bibliographic information and a list of further readings
* The text is geared toward researchers and advanced undergraduate and graduate students

Textauszug

2 AN OVERVIEW OF FRESHWATER HABITATS

James H. Thorp

Department of Biology, Clarkson University, Potsdam, New York 13699

Alan P. Covich

Department of Fishery and Wildlife Biology, Colorado State University, Fort Collins, Colorado 80523

I. Introduction

II. Lotic Environments

A. The Physical–Chemical Milieu

B. Ecosystem Changes Along the Stream Course

III. Underground Aquatic Habitats

A. Hyporheic and Phreatic Zones

B. Aquatic Habitats within Caves and Other Karst Topography

IV. Lentic Ecosystems

A. Geomorphology and Abiotic Zonation of Lakes

B. Biotic Zonation of Lakes

C. Wetlands, Ephemeral Ponds, and Swamps

D. Hypersaline Lakes

Literature Cited

I. INTRODUCTION

The contribution of inland waters to the total biospheric water content is insignificant in terms of percentage (<1% according to Wetzel, 2001) but absolutely crucial from the perspective of terrestrial and freshwater life. Although inland lakes contain 100 times as much water as surface rivers, most lake water is held within massive basins, such as the Laurentian Great Lakes of North America, Lake Baikal of Siberia, and Lake Tanganyika of East Africa. Because most freshwater invertebrates are clustered within shallow, well-lighted zones of lakes, the relative importance of small ponds, creeks, and rivers as habitats for aquatic invertebrates is much greater than their volume percentages would otherwise indicate. Composition, species richness, and total density of invertebrates vary considerably among inland water habitats, as discussed in this chapter.

Distributions of invertebrates are influenced by interactions among physical, chemical, and biological characteristics. The general importance of these abiotic and biotic factors is examined in this chapter. Detailed information on the ecology of individual taxa in inland water ecosystems can be gleaned from Chapters 3–23 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23.

II. LOTIC ENVIRONMENTS

Flowing waters, or lotic environments, were a principal pathway for evolutionary movement of animals from the sea to lakes and land. Even today, many taxa of freshwater invertebrates are restricted to headwater streams and rivers by unique environmental characteristics of these ecosystems. Compared to nonflowing waters, or lentic ecosystems, streams are generally more turbulent than lakes and, therefore, stratification of the water mass with a thermocline is rare. High turbulence generally maintains high oxygen concentrations, reduces within-stream temperature differences, and more evenly distributes plankton and suspended or dissolved nutrients. Temperatures in streams fluctuate over a smaller range than is typical of shallow littoral zones of lentic ecosystems, where most lake-dwelling animals reside (Hynes, 1970). Except in the northernmost rivers, ice is less commonly encountered and is generally not as thick as in lakes. Flowing water habitats frequently possess more habitat heterogeneity, and the food web in forested drainage basins is more dependent on allochthonous production (externally produced plant matter), even though instream production can be important (Thorp and Delong, 1994). Lotic ecosystems are also more permanent on both evolutionary and ecological time frames than most lentic habitats. Both heterogeneity and permanence are thought to increase diversity within these ecosystems.

In this section, we review features of epigean, or surface waters. Characteristics of aquatic environments where water flows underground (hyporheic, phreatic, and cave environments) are discussed in Section III.

A. The Physical–Chemical Milieu

1. Basin Morphometry and Characteristics of Flowing Water

Although stream invertebrates are influenced directly by the physical features of the local habitat and only indirectly by geological forces shaping the morphometry of the entire ecosystem, ecologists and invertebrate zoologists must consider all those factors when attempting to understand what controls community composition. Some elements of stream morphometry that influence aquatic communities are stream order, channel patterns (e.g., meandering and braiding), erosion, deposition, and formation and characteristics of pools and riffles.

Classifying streams by their order, or pattern of tributary connections, is a simple technique that aids analysis of longitudinal (i.e., upstream–downstream) changes in stream characteristics within a single catchment; however, it is less useful, and indeed often misleading for comparing streams in different catchments. For example, communities within streams in the eastern coastal plain bear no close resemblance to communities within similar-order streams in the southwestern deserts (when flooded) (cf. Figs. 1C and 1D respectively). According to this scheme, as refined by Strahler (1952) and illustrated in Figure 2, a continuously running, headwater creek with no permanent tributaries is classified as a first-order stream (permanency is defined here as not being ephemeral on a seasonal or other regular basis). Two first-order streams combine to form a second-order segment; two second-order creeks join as a third-order stream, etc. Stream order increases only when two streams of equivalent rank come together; hence, a third-order stream that flows into a fourth-order system has no effect on the subsequent numbering scale of the larger stream. The Mississippi River, the largest river in North America, attains a stream order of 11–13 in its lower reaches (depending on which maps are used as the basis for analysis). Unfortunately, this scheme is not as useful for many streams in arid portions of the continent where a dry stream bed (Fig. 1D) may be replaced by a raging torrent in a matter of minutes or a few hours.

FIGURE 1 Lower-order streams: (A) Rocky-bed mountain stream in Glacier National Park, Montana; (B) rocky-bed stream from the Smoky Mountains of North Carolina; (C) sandy, coastal plain stream from South Carolina; (D) intermittent, dry-bed stream from Arizona.

(photographs by J. H. Thorp)

FIGURE 2 Bifurcation of streams illustrating the system for classiifying lotic ecosystems according to stream order. The maximum order of the hypothetical stream shown here is sixth.

Viewed from the air, streams clearly do not flow in a simple, straight direction for significant distances (Fig. 3A), nor do stream beds maintain constant depths for long stretches. Instead, the channel traces a meandering pattern of gentle and sharp bends through the basin with alternating bars, pools, and riffles (Fig. 4) as the water travels downstream along a roughly helical path. The distance between meanders is a function of several factors, especially stream width. The river channel also has a tendency to undergo braiding (i.e., the division of the channel into a network of branches) in response to the presence of erodible banks, sediment transport, and large, rapid, and frequent variations in stream discharge (Gordon et al., 1992).

FIGURE 3 (A) Ohio River above Louisville, Kentucky; here the river is meandering with a sandy-gravel bottom and a more laminar flow; (B) Rio Grande near Santa Fe, New Mexico; here this large river is more turbulent than the Ohio River.

(photographs by J. H. Thorp)

FIGURE 4 Schematic drawing of a stream showing straight reaches and meanders. In both sections of a river, a sequence of deep (pools) and shallow (riffle) areas is manifested. Point bars and alternate bars develop as bed material is deposited in areas opposite from the pools. The thalweg, a line connecting the deepest part of the channel, migrates back and forth across the river.

Water flows in a somewhat helical manner along the surface toward an undercutting bank where the deepest pool is usually located and then passes along the bottom toward a “point” or “alternate” sediment bar on the opposite bank from the pool. Sediment is continually being eroded from some areas (e.g., undercut banks and the head of islands) and deposited in other regions (such as on bars and the foot of islands). Successive deepwater pools are separated by shallow riffle regions near the midpoint of two pools. This sequence of bars, pools, and riffles is characteristic of both straight and meandering segments of most rivers, especially those with poorly sorted loads. (See Calow and Petts, 1992; Gordon et al., 1992; and references cited therein...

Produkt-Details

• Erscheint lt. Verlag: 11.5.2001
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Biologie ► Limnologie / Meeresbiologie
• Themenwelt: Naturwissenschaften ► Biologie ► Ökologie / Naturschutz
• Themenwelt: Naturwissenschaften ► Biologie ► Zoologie
• Themenwelt: Naturwissenschaften ► Geowissenschaften ► Hydrologie / Ozeanografie
• Themenwelt: Technik
• ISBN-10: 0-08-053067-2 / 0080530672
• ISBN-13: 978-0-08-053067-3 / 9780080530673