Tide pool

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The site of a tide pool in Santa Cruz, California showing sea stars, sea anemones, and sea sponges. Tide pools in santa cruz.jpg
The site of a tide pool in Santa Cruz, California showing sea stars, sea anemones, and sea sponges.
A tide pool in Porto Covo, west coast of Portugal Porto Covo February 2009-2.jpg
A tide pool in Porto Covo, west coast of Portugal

A tide pool or rock pool is a shallow pool of seawater that forms on the rocky intertidal shore. Many of these pools exist as separate bodies of water only at low tide.


Many tide pool habitats are home to especially adaptable animals that have engaged the attention of naturalists and marine biologists, as well as philosophical essayists: John Steinbeck wrote in The Log from the Sea of Cortez , "It is advisable to look from the tide pool to the stars and then back to the tide pool." [1]

Zones from shallow to deep

Tide pools in Santa Cruz, California from spray/splash zone to low tide zone Tide pools in Santa Cruz from Spray-splash zone to low tide zone.jpg
Tide pools in Santa Cruz, California from spray/splash zone to low tide zone

The rocky shoreline exhibits zonation as a feature of the shoreline. Tidal movements of water creates zonation patterns along rocky shores from high to low-tide. The area above the high-tide mark is the supralittoral zone which is virtually a terrestrial environment. The area around the high-tide mark is known as the intertidal fringe. Between the high and low-tide marks is the intertidal or littoral zone. Below the low-tide mark is the sublittoral or subtidal zone.

The presence and abundance of animals and algae vary between zones along the rocky shore due to niche adaptations in response to the varying levels of tidal and solar exposure.

Tide pools exist in the "intertidal zone" (the area within the tidal range), which is submerged by the sea at high tides and during storms, and may receive spray from wave action. At other times the rocks may undergo other extreme conditions, baking in the sun or exposed to cold winds. Few organisms can survive such harsh conditions. Lichens and barnacles live in this zone. [1] Different barnacle species live at very tightly constrained elevations, with tidal conditions precisely determining the exact height of an assemblage relative to sea level.

The intertidal zone is periodically exposed to sun and wind, conditions that can cause barnacles to become desiccated. These animals, therefore, need to be well adapted to water loss. Their calcite shells are impermeable, and they possess two plates which they slide across their mouth opening when not feeding. These plates also protect against predation. [2]

High tide zone

The high tide zone is flooded during each high tide. Organisms must survive wave action, currents, and exposure to the sun. This zone is predominantly inhabited by seaweed and invertebrates, such as sea anemones, sea star, chitons, crabs, green algae, and mussels. Marine algae provide shelter for nudibranchs and hermit crabs. The same waves and currents that make life in the high tide zone difficult bring food to filter feeders and other intertidal organisms.

Low tide zone in a tide pool Pteropurpura trialata is laying the eggs 1.jpg
Low tide zone in a tide pool

Low tide zone

Also called the "lower littoral zone", this area is mostly submerged and is exposed only during unusually low tide. [1] It often teems with life and has far more marine vegetation, especially seaweeds. There is also greater biodiversity. Organisms in this zone do not have to be as well adapted to drying out and temperature extremes. Low tide zone organisms include abalone, anemones, brown seaweed, chitons, crabs, green algae, hydroids, isopods, limpets, mussels, and sometimes even small vertebrates such as fish. These creatures can grow to larger sizes because there is more available energy and better water coverage: the water is shallow enough to allow additional sunlight for photosynthetic activity, with almost normal levels of salinity. This area is also relatively protected from large predators because of the wave action and shallow water.

Marine life

Tide pools provide a home for hardy organisms such as sea stars, mussels and clams. Inhabitants must be able to deal with a frequently changing environment: fluctuations in water temperature, salinity, and oxygen content. Hazards include waves, strong currents, exposure to midday sun and predators.

Waves can dislodge mussels and draw them out to sea. Gulls pick up and drop sea urchins to break them open. Sea stars prey on mussels and are eaten by gulls themselves. Black bears are known to sometimes feast on intertidal creatures at low tide. [3] Although tide pool organisms must avoid getting washed away into the ocean, drying up in the sun, or being eaten, they depend on the tide pool's constant changes for food. [1]


The sea anemone Anthopleura elegantissima reproduces clones of itself through a process of longitudinal fission, in which the animal splits into two parts along its length. [4] The sea anemone Anthopleura sola often engages in territorial fights. The white tentacles (acrorhagi), which contain stinging cells, are for fighting. The sea anemones sting each other repeatedly until one of them moves. [5]

Some species of sea stars can regenerate lost arms. Most species must retain an intact central part of the body to be able to regenerate, but a few can regrow from a single ray. The regeneration of these stars is possible because the vital organs are in the arms. [6]

Sea Urchins ("Echinoidia") move around tide pools with tube like feet. Different species of urchin have different colors, and many are seen in tide pools. With spines, some filled with poison like with "Toxopnesutes pileolus", that protect them from predators they feed almost undisturbed in tide pools. Algae and other microorganism are the food sources that attract them to the tide pools. {{cite news http://californiatidepools.com/sea-urchins/ }}</ref>


Sea palms ( Postelsia ) look similar to miniature palm trees. They live in the middle to upper intertidal zones in areas with greater wave action. High wave action may increase nutrient availability and moves the blades of the thallus, allowing more sunlight to reach the organism so that it can photosynthesize. In addition, the constant wave action removes competitors, such as the mussel species Mytilus californianus .

Recent studies have shown that Postelsia grows in greater numbers when such competition exists; a control group with no competition produced fewer offspring than an experimental group with mussels; from this it is thought that the mussels provide protection for the developing gametophytes. [7] Alternatively, the mussels may prevent the growth of competing algae such as Corallina or Halosaccion , allowing Postelsia to grow freely after wave action has eliminated the mussels. [8]

Coralline algae "Corallinales" are predominant features of mid and low intertidal tide pools. Calcium carbonate (CaCO3) takes the form of calcite in their cell walls providing them with a hard outer shell. This shell protects from herbivores and desiccation due to lack of water and evaporation. Many forms of the Coralline algae bring herbivores, such as mollusks "Notoacmea", to the tide pools during high tides, increasing the biomass of the area. Once low tides comes, these herbivores are exposed to carnivores in the areas, fueling the food web. [9]

See also

Related Research Articles

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The littoral zone or nearshore is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark to coastal areas that are permanently submerged — known as the foreshore — and the terms are often used interchangeably. However, the geographical meaning of littoral zone extends well beyond the intertidal zone to include all neritic waters within the bounds of continental shelves.

<i>Hormosira</i> Species of Phaeophyceae

Hormosira banksii, also known as Neptune's necklace, Neptune's pearls, sea grapes, or bubbleweed) is a species of seaweed native to Australia and New Zealand. The genus Hormosira is monotypic.

<span class="mw-page-title-main">Coralline algae</span> Order of algae (Corallinales)

Coralline algae are red algae in the order Corallinales. They are characterized by a thallus that is hard because of calcareous deposits contained within the cell walls. The colors of these algae are most typically pink, or some other shade of red, but some species can be purple, yellow, blue, white, or gray-green. Coralline algae play an important role in the ecology of coral reefs. Sea urchins, parrot fish, and limpets and chitons feed on coralline algae. In the temperate Mediterranean Sea, coralline algae are the main builders of a typical algal reef, the Coralligène ("coralligenous"). Many are typically encrusting and rock-like, found in marine waters all over the world. Only one species lives in freshwater. Unattached specimens may form relatively smooth compact balls to warty or fruticose thalli.

<span class="mw-page-title-main">Aggregating anemone</span> Species of sea anemone

The aggregating anemone, or clonal anemone, is the most abundant species of sea anemone found on rocky, tide swept shores along the Pacific coast of North America. This cnidarian hosts endosymbiotic algae called zooxanthellae that contribute substantially to primary productivity in the intertidal zone. The aggregating anemone has become a model organism for the study of temperate cnidarian-algal symbioses.

<span class="mw-page-title-main">Intertidal zone</span> Area of coast exposed only at low tide

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<span class="mw-page-title-main">Intertidal ecology</span>

Intertidal ecology is the study of intertidal ecosystems, where organisms live between the low and high tide lines. At low tide, the intertidal is exposed whereas at high tide, the intertidal is underwater. Intertidal ecologists therefore study the interactions between intertidal organisms and their environment, as well as between different species of intertidal organisms within a particular intertidal community. The most important environmental and species interactions may vary based on the type of intertidal community being studied, the broadest of classifications being based on substrates—rocky shore and soft bottom communities.

<span class="mw-page-title-main">Rocky shore</span> Intertidal area of coast where solid rock predominates

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<span class="mw-page-title-main">Ballantine scale</span> Marine biology measurement scale

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<span class="mw-page-title-main">Davenport tide pools</span>

The Davenport Tide Pools are located just past the town of Davenport, California in the United States. They are located off Davenport Landing, which is a street off Highway 1. The tide pools are unique due to the ridges that run up and down the tide pools, allowing for different organisms to live close, even though in a normal habitat they would be unable to do so. The Beach is open sunrise to sunset, and is day use only.

<i>Anthopleura xanthogrammica</i> Species of coral

Anthopleura xanthogrammica, or the giant green anemone, is a species of intertidal sea anemone of the family Actiniidae.

<i>Lottia digitalis</i> Species of gastropod

Lottia digitalis, the fingered limpet or ribbed limpet, is a species of sea snail, a true limpet, a marine gastropod mollusk in the family Lottiidae. These limpets are usually found on the surface of rocks in the high intertidal region on the coastal fringes of the northeast Pacific Ocean.

<span class="mw-page-title-main">Montagu's blenny</span> Species of fish

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<span class="mw-page-title-main">Marine habitats</span> Habitat that supports marine life

Marine habitats are habitats that support marine life. Marine life depends in some way on the saltwater that is in the sea. A habitat is an ecological or environmental area inhabited by one or more living species. The marine environment supports many kinds of these habitats. Marine habitats can be divided into coastal and open ocean habitats. Coastal habitats are found in the area that extends from as far as the tide comes in on the shoreline out to the edge of the continental shelf. Most marine life is found in coastal habitats, even though the shelf area occupies only seven percent of the total ocean area. Open ocean habitats are found in the deep ocean beyond the edge of the continental shelf.

<i>Stichaster australis</i> Species of starfish

Stichaster australis, the reef starfish, is a species of starfish found in the shallow waters of the rocky intertidal of New Zealand. Typically, the animal is endemic to the west coast shores of the North and South Islands, where wave action is increased. They do not usually inhabit ecosystems that have reduced wave action and calm conditions as they prefer a higher-energy environment. These marine invertebrates range in color from pink to purple, but can also be orange. They typically have eleven arms, but sometimes they may have either ten or twelve. As full-grown adults, they are 8 to 10 cm in diameter.

<i>Pollicipes polymerus</i> Species of crustacean

Pollicipes polymerus, commonly known as the gooseneck barnacle or leaf barnacle, is a species of stalked barnacle. It is found, often in great numbers, on rocky shores on the Pacific coasts of North America.

<i>Spongites yendoi</i> Species of alga

Spongites yendoi is a species of crustose red seaweed with a hard, calcareous skeleton in the family Corallinaceae. It is found on the lower shore as part of a diverse community in the southeastern Atlantic Ocean and the Indo-Pacific Ocean.

Anthopleura thallia, commonly known as the glaucous pimplet, is a species of sea anemone in the family Actiniidae. It is found in shallow water in the northeastern Atlantic Ocean and the Mediterranean Sea.

The Stilbaai Marine Protected Area is an inshore conservation region in the territorial waters near Stilbaai on the south coast of the Western Cape province of South Africa.


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  9. Padilla, Dianna K. (July 24, 1984). "The importance of form: Differences in competitive ability, resistance to consumers and environmental stress in an assemblage of coralline algae". Journal of Experimental Marine Biology and Ecology. 79 (2): 105–127. doi:10.1016/0022-0981(84)90213-2. ISSN   0022-0981.