Encyclopedia of Tidepools and Rocky Shores

Preface

xxvii Rocky shores lie at the interface between the land and the sea, experiencing a Jekyll-and-Hyde existence of alternating terrestrial and marine habitats. When the tide is in, coastal plants and animals are bathed by seawater that exposes them to predators, moderates temperatres, delivers food, transports propagules, and imposes large hydrodynamic forces. When the tide is out, the same rocky-shore species are subjected to terrestrial predators, desiccation, temperature extremes, intense solar radiation, and occasional dousing by freshwater. Intertidal organisms must survive in both terrestrial and marine worlds, transitioning as often as twice each day as the tides ebb and flow. One might easily suppose that the physical and biological rigors of the shore would be sufficient to exclude all but a few plants and animals. What terrestrial animal could withstand both the pounding of waves and the cyclical change in temperature characteristic of the shore? What delicate sea creature could survive being baked for hours in the sun? Yet, despite such adversity, rocky shores are home to a striking diversity of species. As John Steinbeck famously noted upon approaching a waveswept shore in Mexico: “The exposed rocks had looked rich with life under the lowering tide, but they were more than that: they were ferocious with life.” Mussels, sculpins , kelps, and urchins; anemones and sea stars of all sizes and colors; barnacles, worms, limpets, and abalone; algae that look like corals; others that look like tar—the diversity of rocky shores rivals that of tropical rainforests. This diversity is a rich source of wonder and the cause for curiosity. For many people, rocky shores at low tide provide the only opportunity to see and interact with marine species firsthand. Go down to the shore and poke around. Kneel down and stare into a tidepool. Comb through the seaweeds to see what lies beneath. Undoubtedly, questions will rapidly spring to mind. At first, they may be specific and small-scale. What species is that snail? Do seagrasses really have flowers? What do sea anemones eat? But small questions lead to larger ones: How do these marine organisms survive exposure to air? How did these intertidal animals and algae, seemingly immobile, get here? How do interactions between species affect where they occur and how abundant they are? In this encyclopedia, we strive to provide answers to these types of questions, both small and large. The extent to which we can provide these answers—as indicated by the heft of this tome—is testament to the intellectual attraction of wave-swept shores. Rocky coasts are not merely a curious oddity among Earth’s habitats; they have proven scientific value. To cite a prime example , thanks to their steep environmental gradient, their two-dimensional structure, and the rapid turnover of their abundant sessile or slow-moving organisms, waveswept rocky shores make it practical for ecologists to conduct experiments that would be difficult or impossible elsewhere. Much of what we know about the ecological importance of processes such as competition, recruitment , predation, and patch dynamics has been tested on rocky shores. Although rocky shores are a comparatively minor habitat on Earth in terms of area, they have played a disproportionately large role in our understanding of ecological systems. As we move into an era of accelerated global climate change and expanded human domination of ecosystems, the extensive past work in the intertidal zone may serve as a valuable baseline against which to measure the effects of environmental shifts. Our goal here of providing answers is constrained by several factors. First, many questions in intertidal science remain unresolved. As you delve into this book, you will find many articles noting the limitations of present knowledge. But that is how science works. Noting the PREFACE things we do not yet understand is as important as cataloging the things we do know. If you find yourself frustrated by the lack of an answer to a particular question, jump right in and explore the topic yourself. We hope that the information provided here will at least provide a basis from which to proceed. Second, even for a volume that professes to be encyclopedic , it was impossible to cover everything. For example, with few exceptions, we have limited ourselves to discussion of intertidal and shallow subtidal zones of rocky shores. As a consequence, there is little here that deals with sandy beaches and coral reefs. Even within this restricted scope, choices had to be made. A few topics were left out because we...