Tide pools

Conover, J.T. and Sieburth, J., Effects of tannins excreted from Phaeophyta on planktonic animal survival in tide pools, Proc. 5th Int. Seaweed Symp., 99, 1966. 

Man is. . . related inextricably to all reality, known and unknowable. .. plankton, a shimmering phosphorescence on the sea and the spinning planets and an expanding universe, all bound together by the elastic string of time. It is advisable to look from the tidal pool to the stars and then back to the tide pool again. 

The shore is part of a larger zone referred to as the coast, the entire area that is affected by the sea. The coast includes the familiar sand and surf, as well as mud flats, tide pools, and marshes. The coast begins at the point where waves start breaking as they roll in toward the shore, and it extends to the farthest reaches of waves and tides on land. In some localities, the distance between the first breaking waves and the highest tides is just a matter of meters in others, it encompasses miles. 

Hard, rocky substrates are characteristic of tide pools, little puddles of seawater that are left behind when high tide recedes. The conditions in tide pools are extremely variable, and the organisms that live there are specialized to these conditions. Tide pools are dynamic environments that are alternately wet and dry. Inhabitants are adapted to cling to rocky surfaces when water rushes into tide pools, and to conserve moisture when water levels are low. 

Mud flats are subject to the coming and going of tides, but unlike beaches and tide pools, they are protected from waves. Water cannot drain through muddy soil like it does on beaches where soil particles are loosely packed. Mud particles are small and tightly packed, so they hold water in place. When water occupies the spaces between mud particles, there is no room for oxygen. As a result, mud flats are anaerobic environments that support only organisms that can survive in low or no oxygen. 

One sponge species found in many coastal zones is the breadcrumb sponge (Halichondria panicea). Green to yellow crusts of the sponge creep across rocks and can cover an area of several feet. Breadcrumb sponges can be found as thin mats in the energetic surf zones, but in quiet tide pools, they form thicker masses. 

Unlike hydrozoids, jellyfish are cnidarians that spend their entire lives in the medusa form. Most live in water deeper than the intertidal area, but individuals sometimes stray or wash into the shallow water of the surf. One very unusual type of jellyfish is native to the intertidal zone, the stalked jellyfish (Haliclystus). Instead of the usual medusa form, the body of the stalked jellyfish is attached to the substrate by a stalk on which the medusa is flipped upside down, with the mouth facing up, giving the animal the appearance of a flower. The petals of the flower are eight lobes that are tipped with club-like tentacles. Haliclystus auricula is one kind of stalked jellyfish whose lobes end in hundreds of tentacles. This very small jellyfish, reaching l4 inches (4.45 cm) in height, favors quiet tide pools where it may be found attached to snails, seaweed, or rocks. H. auricula feeds on worms and other small shore animals. 

The oyster flatworm (Stylochus ellipticus) lives in tide pools and under rocks. This cream-colored organism has a narrow band of eyespots and a fringe of tiny tentacles on its anterior end. Oyster flatworms, which can grow up to 1 inch (2.5 cm) long, feed on barnacles as well as oysters. 

Cnidarians represent a higher level of complexity than sponges. Their bodies are saclike structures with only one opening to the digestive system. Tentacles around the mouth are used for food gathering as well as for defense. Anemones are common in tide pools, where many form colonies that are efficient at conserving water and dispersing the force of the waves. 

Once or twice each day, seawater floods across the intertidal rocks, mudflats, and sands. As it recedes, some is trapped in rocky depressions and low spots, creating tiny pockets of water called tide pools. A tide pool is a miniature seawater ecosystem that supports an astonishing variety of living things, including small bony fish. The largest group of vertebrates in the sea, fish are well represented in the intertidal zone. 

Like all sculpins, tide pool sculpins are highly adapted for their environments and have developed a variety of structures... 

The ability to change colors to match their surroundings helps tide pool sculpins blend with the environment, enabling the fish to avoid many predators and providing them with camouflage while they wait to ambush their own prey. Their diet consists of crabs, shrimp, and the eggs of insects and other fish. 

Wooly sculpins spawn all year long, but the peak season is from November to May. The female deposits her eggs in nests where they are fertilized by males. Unlike many other tide pool fish, neither sculpin parent stays behind to guard the eggs, which generally hatch within 13 to 18 days. 

The zebra blenny (Istiblennius zebra), which is about 6 inches (15.3 cm) long at maturity, makes its home in the intertidal zone of the Hawaiian Islands. The body color varies from blue to yellow, but it is the distinctive dark, vertical stripes along the fish s side that account for its common name. The zebra blenny uses its pelvic fins as props to support its head high in the water, a position that enables the animal to watch for predators and prey. Distinctive, tentacle-like cirri extend down over its eyes. This tiny fish can curl its tail to one side like a coiled spring, then forcefully unfurl it to jump into a nearby tide pool. 

The suction cup of the clingfish serves more than one purpose. Not only does it enable the fish to hang on, but it also holds water when conditions are dry. After the tide goes out, the water level in a tide pool can fall dangerously low. If this happens, the fish uses the moisture held within the suction cup to breathe. Sheltered beneath a rock or within the crevice of a rock, it takes in oxygen from the trapped moisture and waits until the tide rolls back in with a fresh supply of water, oxygen, and nutrients. 

Sculpins are small but conspicuous fish in tide pool environments. A sculpin only grows to about 3 inches (7.5 cm) in length, and its coloration is either green or red with five irregular dark circles. The head is large in proportion to the rest of the slim, elongated body. If washed out of its home tide pool, a sculpin can use chemoreceptors to identify the specific chemical combinations that mark its home and then eventually make its way back to it. 

Blennies, known as rock skippers because they are able to jump from one tide pool to another, also live in tide pools. During the breeding season, male blennies change color and carry out ritualized breeding activities. After the eggs are laid, the male protects them until they hatch. 

All species of tide pool fish face unusual environmental conditions and possess special adaptations to help them survive in this unique situation. Like other vertebrates in the ocean, fish are consumers that feed near the top of the food chain and important members of shoreline ecosystems. 

This very small octopus, measuring no more than 7.8" across spread tentacle, can be found from Japan to Australia in shallow tropical water and in tide pools, where it skillfully hunts for crabs and other crustaceans. They are given the blue ring name because they will display differently shaped rings or stripes of blue when excited. When not agitated or mating, the octopus has a natural camouflage that imposes a -5 to normal attempts to detect the creature. 

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