PHYSIOLOGICAL ECOLOGY A Series of Monographs, Texts, and Treatises EDITED BY T. T. KOZLOWSKI University of Wisconsin Madison, Wisconsin T. T. KOZLOWSKI. Growth and Development of Trees, Volumes I and II - 1971 DANIEL HILLEL. Soil and Water: Physical Principles and Processes, 1971 J. LEVITT. Responses of Plants to Environmental Stresses, 1972 V. B. YOUNGNER AND C. M. MCKELL (Eds.). The Biology and Utilization of Grasses, 1972 T. T. KOZLOWSKI (Ed.). Seed Biology, Volumes I, 11, and 111 - 1972 YoAV WAISEL. Biology of Halophytes, 1972 G. C. MARKS AND T. T. KOZLOWSKI (Eds.). Ectomycorrhizae: Their Ecol­ ogy and Physiology, 1973 T. T. KOZLOWSKI (Ed.). Shedding of Plant Parts, 1973 ELROY L. RICE. Allelopathy, 1974 T. T. KOZLOWSKI AND C. E. AHLGREN (Eds.). Fire and Ecosystems, 1974 J. BRIAN MUDD AND T. T. KOZLOWSKI (Eds.). Responses of Plants to Air Pollution, 1975 REXFORD DAUBENMIRE. Plant Geography, 1978 JOHN G. SCANDALIOS (Ed.), Physiological Genetics, 1979 BERTRAM G. MURRAY, JR. Population Dynamics: Alternative Models, 1979 J. LEVITT. Responses of Plants to Environmental Stresses, 2nd Edition. Volume 1: Chilling, Freezing, and High Temperature Stresses, 1980 Volume II: Water, Radiation, Salt, and Other Stresses, 1980 JAMES A. LARSEN. The Boreal Ecosystem, 1980 SIDNEY A. GAUTHREAUX, JR. (Ed.), Animal Migration, Orientation, and Navigation, 1981 F. JOHN VERNBERG AND WINONA B. VERNBERG (Eds.), Functional Adap­ tations of Marine Organisms, 1981 Functional Adaptations of Marine Organisms Edited by F. JOHN VERNBERG Belle W. Baruch Institute for Marine Biology and Coastal Research University of South Carolina Columbia, South Carolina WINONA B. VERNBERG College of Health University of South Carolina Columbia, South Carolina 1981 ACADEMIC PRESS A Subsidiary of Harcourt Brace Jovanovich, Publishers New York London Toronto Sydney San Francisco Copyright © 1981, by A c a d e m ic Press, Inc. a ll rights reserved. NO PART OF THIS PUBLICATION M AY BE REPRODUCED OR TRANSMITTED IN ANY F O RM OR BY ANY MEANS, ELECTRONIC OR MECHANICAL, INCLUDING PHOTOCOPY, RECORDING, OR ANY INFORMATION STORAGE AND RETRIEVAL SYSTEM, W I T H O UT PERMISSION IN WRITING F R OM THE PUBLISHER. ACADEMIC PRESS, INC. Ill Fifth Avenue, N ew York, N ew York 10003 United Kingdom Edition published by ACADEMIC PRESS, INC. (LONDON) LTD. 24/28 Oval Road, London N Wl 7 DX Library of Congress Cataloging in Publication Data Main entry under title: Functional adaptations of marine organisms. (Physiological ecology series) Includes bibliographies and index. 1. Marine fauna—Physiology. 2. Marine flora- Physiology. 3. Adaptation (Physiology) I. Vernberg, F. John, Date. II. Vernberg, Winona B., Date. III. Series. QL121.F86 57A.5»2636 8٢-168A ISBN 0-12-718280-2 PRINTED IN THE UNITED STATES OF AMERICA 81 82 83 84 9 8 7 6 5 4 3 2 1 List of Contributors Numbers in parentheses indicate the pages on which the authors' contributions begin. Bruce W. Belman (231), Department of Biology, University of Califomia, Los Angeles, Califomia 90024 Thomas H. Chrzanowski (71), Department of Biology, Belle W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina, Columbia, South Carolina 29208 Bruce C. Coull (147), Belle W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina, Columbia, South Carolina 29208 Randolph L. Ferguson (9), National Marine Fisheries Service, NOAA, South­ east Fisheries Center, Beaufort Laboratory, Beaufort, North Carolina 28516 Robert Y. George (279), Institute of Marine Biomedical Research, University of North Carolina at Wilmington, Wilmington, North Carolina 28401 Malcolm S. Gordon (231), Department of Biology, University of Califomia, Los Angeles, Califomia 90024 Donald R. Heinle'^ (85), Chesapeake Biological Laboratory, University of Mary­ land Center for Estuarine Environmental Studies, Solomons, Maryland 20688 Theodore R. Rice (9), National Marine Fisheries Service, NOAA, Southeast Fisheries Center, Beaufort Laboratory, Beaufort, North Carolina 28516 L. Harold Stevenson (71), Department of Biology, Belle W. Bamch Institute for Marine Biology and Coastal Research, University of South Carolina, Col­ umbia, South Carolina 29208 Gordon W. Thayer (9), National Marine Fisheries Service, NOAA, Southeast Fisheries Center, Beaufort Laboratory, Beaufort, North Carolina 28516 •Present address: CH2M Hill, Bellevue, WA 98004 ix χ List of Contributors F. John Vernberg (1, 179), Belle W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina, Columbia, South Carolina 29208 Winona B. Vernberg (1, 147), College of Health, University of South Carolina, Columbia, South Carolina 29208 Preface To function is to live. To the scientist concerned with understanding how organisms function in their environment, the sea offers diverse marine biota which are subject to very different sets of environmental factors, thereby provid­ ing an unequalled source of experimental material. The marine biota offer an opportunity to study organismic responses to '^natural" sets of environmental factors as well as man-made sets of perturbations, whether they be the introduc­ tion of foreign substances, dredging, off-shore drilling, or overfishing. This book is written to provide an insight into some of the functional adapta­ tions of marine organisms to both natural and man-made sets of factors. It is organized into chapters representing an ecological orientation. The physiology of plants is presented in terms of both primary producers and decomposers, while functional adaptations of animals are discussed in relation to the major ecological divisions of the sea: Zooplankton, meiofauna, benthic macroinvertebrates, and pelagic and deep-sea organisms. We have also written for both marine and nonmarine scientists who have broad interests in acquiring knowledge about the adaptations of organisms in changing environments. We hope that students, our hope for future progress, will be particularly stimulated, learn what has been accomplished, and then, with enthusiasm, seek answers both to persistent and to new problems. F. John Vernberg Winona B. Vernberg xi 1 Introduction F. J. Vernberg and W. B. Vernberg I. Introduction 1 II. Oceanic Habitats 2 in. The Intertidal Zone 5 IV. Estuaries 5 V. Coastal and Open Ocean Waters 6 VI. The Deep Sea 7 I. Introduction In recent years society has shown an unprecedented interest in the dynamic impact of environment on plants and animals. Not only has this ecological awareness stirred the thoughts and emotions of the layman, but also scientists from diverse scientific disciplines have become professionally involved. As would be expected, this diversity of scientific input inevitably has led to a greater understanding of the interrelationships between organisms and their environ­ ment. At the same time, the boundary lines of older scientific disciplines have become blurred, and new ones have emerged. Physiological ecology is an excel­ lent example of a newly forged discipline which has come to the forefront in recent years by drawing on the expertise of scientists who often come from traditional scientific backgrounds. This field is concerned with understanding the basic mechanisms of organismic response to the surrounding environmental complex. Physiological ecologists attempt to interpret physiological responses in terms of their adaptive environmental significance, viewing each organism as a highly integrated system of multiple functional components that may be dif­ ferentially influenced by environmental factors. The functioning of these compo­ nent parts must be integrated to ensure that the intact organism can survive and perpetuate the species. Although the principal unit of study is the individual organism, it is obvious that the organism is both part of a population and of the ecosystem containing this population. Thus, physiological ecologists are concerned with the physiological attributes of populations and communities based on responses of individuals. This continuum of interest over a range of responses from the molecular to the community level of biological organization is necessary to gain insight into the adaptive significance of these responses. The breadth of interest in ecology is restricted only by the vision of the individual investigator and not by artificially FUNCTIONAL ADAPTATONS OF MARINE ORGANISMS 1 Copyright © by Academic Press, Inc. All rights of reproduction in any form reserved. ISBN 0-12-718280-2 2 F. J. Vernberg and W. Β. Vernberg imposed discipline boundaries. Thus, while physiological ecologists may vary in their background and training, they are unified by their interest in understanding a very fundamental question; how and why do organisms live where they do? Each organism is exposed to an external environment that consists of a com­ plex combination of interesting factors. Internally the functional machinery must respond to these factors in such a way that the organism can survive. For our convenience in analyzing this environmental-organismic interaction, the external environment can be divided into abiotic and biotic factors. Abiotic factors are numerous and include temperature, salinity, geomagnetic forces, multiple chem­ ical substances, gases, hydrostatic pressure, light, and currents. In the biotic category are such factors as predator-prey interaction, commensalism, and com­ petition. Both biotic and abiotic factors can interact significantly to influence an organism. For example, low oxygen concentrations may adversely affect the ability of a prey species to escape from its predator. Of interest to the theme of this book is the observation that the dynamic equilibrium between the organism and its environment is constantly changing with time and fluctuation in the several components acting individually or in concert. A combination of factors that results in the death of an organism is termed the zone of lethality. When studying a single factor, there is typically a lethal point at a high and low expression of this factor. Between these "high" and **low" lethal points, there is a broad range of sublethal environmental combinations that influence the organism, known as the zone of compatibility. Within the zone of compatibility an organism may survive, but its ability to function efficiently may be markedly reduced. For example, a sublethal temperature may allow the organism to move about and feed, but curtail the reproductive potential to such an extent that the species cannot survive. The oceanic biota represents a particular challenge to the physiological ecologist—what are the functional ploys that the diverse species from markedly different habitats utilize to survive and reproduce? Briefly, let us now consider some of the multiplicity of habitats within the marine environment. II. Oceanic Habitats The sea, with a volume of approximately 315 million cubic miles, covers over 71% of the earth's surface. Although tremendously vast, the unity of the sea environment is demonstrated in that the entire seawater mass is continuous, so that a drop of water could potentially make its way to any part of the total sea. In recent years, the topographical density of the ocean floor has been established by mapping. We now know that there are sea mountains with peaks that break the ocean surface to form small islands, tremendously deep trenches that cleave the ocean floor (such as the 35,800 foot Mindanao Trench), and a submerged 1. Introduction 3 mountain range (mid-Atlantic ridge) that extends for 10,000 miles in the North Atlantic Ocean. The ocean floor is now considered to be a dynamic system owing to the concepts of continental drift, seafloor spreading, and plate tectonics. On a geological time scale, a habitat at one specific geographical location changes constanfly, and the populations of organisms that live there must adapt to new environmental stresses in an evolutionary sense. An understanding of the physiological ecology of these organisms is a great challenge. Numerous classifications of marine environments have been proposed, but the one that has been most widely excepted is graphically represented in Fig. 1. This classification was proposed by the Committee on Marine Ecology and Paleoecol- ogy. The two major divisions of this classification are benthic and pelagic, and these may be further subdivided. Each assemblage contains a characteristic fauna and flora. Benthic environments extend from high ground to the ocean depths and have been divided into six different zones; (1) supralittoral, (2) littoral or interti­ dal, (3) sublittoral, (4) bathyal, (5) abyssal, and (6) hadal. The regions of the deep sea are the least well defined, although this area is the largest benthic habitat type, occupying nearly 90% of the ocean floor. The pelagic region can be divided into two main areas; the neretic zone, which comprises the water mass over the Continental Shelf, and the oceanic zone, which includes the main mass of seawa­ ter. The oceanic region may further be divided into four sub-regions; (1) the epipelagic, (2) mesopelagic, (3) bathypelagic, and (4) the abyssopelagic. Marine environments may also be described ecologically. A good illustration are those terms that refer to the amount of light since light steadily decreases in intensity with increasing depth. The terms aphotic and euphotic generally denote regions of darkness or light. Other bases have been proposed to describe marine environments by referring to a general region of the sea, such as divisions of shore and shallow water seas, or to taxonomic groups, such as the level bottom molluscan community or the laminarian intertidal zone. Marine organisms may also be classified on the basis of the habitat type in which they live. For example, benthic organisms are associated with the bottom substrata; those species as­ sociated with the surface of the bottom are the epifauna while those that dig or are buried in the substratum are the infauna. Benthic organisms may be further divided into groups based on size; macrobenthos are organisms too large to pass through a 1 mm mesh sieve, meiobenthos are organisms smaller than the mac­ robenthos, but which are retained by 0.1 mm mesh sieve, and the microbenthos are organisms that are so small that they pass freely through a 0.1 mm mesh sieve. Free-moving organisms that inhabit the water column are called pelagic species, those that can control direction and speed of locomotion are called the nekton, and those primarily dependent on water movement for location or locomotion are called plankton. In turn, plankton are generally recognized as being either phytoplankton (the plant species) or Zooplankton (the animal species). Nannoplankton are small plankton ranging in length from 5 to 60 ^m. 1 •o F a M thom et e s r s S g 8 g -J— SS l - H — ^ -Γ -· r - r ' — h - T - ^ V + o * Fig. 1. Classification of marine environments. From J. W. Hedgpeth, 1957. In "Treatise on Marine Ecology and Paleoecology" (J. W. Hedgpeth, ed.). Vol. 1, Geol. Soc. Am. Mem. No. 67, New York, pp. 17-28.