Life on Intertidal Rocks: A Guide to the Marine Life of the Rocky North Atlantic Coast (Nature Study Guides) - Softcover

Day, Cherie Hunter

Softcover

ISBN 10: 0912550155 ISBN 13: 9780912550152

Publisher: Nature Study Guild Publishers, 1987

Synopsis

This pocket-sized field guide identifies plants and animals that live in the intertidal zone of the rocky coast, from Cape Cod north to the Bay of Fundy, in tide pools, caves, and crevices, and on rocks, wharves and pilings. Explains intertidal ecology and how these fascinating and varied creatures--sea slugs, crabs, rockweeds, star fish, and many others--survive in the harsh and ever-changing environment between the limits of high and low tide.

About this title

Excerpt. © Reprinted by permission. All rights reserved.:

Intertidal Life
Formation of the Rocky Coast

The rocky coast of the Gulf of Maine, with wave-beaten headlands, narrow sheltered bays, steep, rocky cliffs, and many islands, was shaped by Ice Age glaciers. Sheets of ice up to a mile thick advanced as far south as Cape Cod, scouring away sediment. As they retreated, the melting glaciers exposed the granite bedrock and left behind boulders and gravel. This made an intertidal habitat with many places for organisms to hide, and a firm substrate for them to grip--a rocky habitat quite different from the shifting beach sediments of the Atlantic coast south of Cape Cod.

Water Temperature

Water temperature determines where a plant or animal lives. Each intertidal organism has a range of temperatures in which it can flourish. Beyond this optimal range it can survive only by adapting to local conditions. The hook of Cape Cod juts into the Atlantic Ocean and acts as a barrier between cold temperate waters in the Gulf of Maine and warmer waters to the south. Some species occur only in the Gulf of Maine. Others, more abundant south of Cape Cod, have adapted to the cooler waters by moving into higher, warmer levels of the intertidal zone, or by completing their life cycles during the warmer months. Some are confined locally to sheltered bays. Conversely, intertidal species common in the arctic may be found in the Gulf of Maine at lower intertidal and subtidal levels.

Adaptations

Intertidal plants and animals must contend with a wide variety of environmental stresses. Twice daily they tolerate submersion and exposure to air and sunlight. Storms with crashing waves threaten to rip organisms off their substrates. Predators are a constant menace.

The seasons bring dramatic changes. Ice scrapes creatures off exposed rocks and freezes shallow tide pools, trapping the inhabitants. Some animals can escape winter cold by moving to deeper water, but attached organisms die back or become dormant, waiting for spring. In summer heat, animals can suffocate, since warm water holds less dissolved oxygen.

Salinity (salt concentration) changes as rivers swollen with melted ice and snow dilute coastal waters in the spring. Shallow tide pools have the widest range of salinity, as rain dilutes or the sun evaporates the water. Few intertidal creatures can tolerate the brackish water of estuaries, where salt water intrudes only at high tide.

Despite all these difficulties, intertidal rocks are crowded with creatures competing for food and shelter.

About this edition

• Publisher: Nature Study Guild Publishers
• Publication date: 1987
• ISBN 10: 0912550155
• ISBN 13: 9780912550152
• Binding: Paperback
• Number of pages: 64