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

Tide pools or rock pools are shallow pools of seawater that form on the rocky intertidal shore. Many of these pools exist as separate bodies of water only at low tide.


Many tide pools are habitats of 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

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, starfish, chitons, crabs, green algae, and mussels. Marine algae provide shelter for nudibranches 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 starfish, 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. Starfish 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 starfish 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 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]

See also

Related Research Articles

Marine biology The scientific study of organisms that live in the ocean

Marine biology is the scientific study of marine life, organisms in the sea. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather than on taxonomy.


Benthos, from the Greek benthos meaning "depth of the sea", is the community of organisms that live on, in, or near the seabed, river, lake, or stream bottom, also known as the benthic zone. This community lives in or near marine or freshwater sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths.

Littoral zone Part of a sea, lake or river that is close to the shore

The littoral zone or nearshore is the part of a sea, lake, or river that is close to the shore. In coastal environments, the littoral zone extends from the high water mark, which is rarely inundated, to shoreline areas that are permanently submerged. The littoral zone always includes this intertidal zone, and the terms are often used interchangeably. However, the meaning of littoral zone can extend well beyond the intertidal zone.

Aggregating 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.

Intertidal zone Area of coast exposed only at low tide

The intertidal zone, also known as the foreshore or seashore, is the area above water level at low tide and underwater at high tide. This area can include several types of habitats with various species of life, such as seastars, sea urchins, and many species of coral. Sometimes it is referred to as the littoral zone, although that can be defined as a wider region.

Intertidal ecology

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.

Rocky shore An intertidal area of coast where solid rock predominates

A rocky shore is an intertidal area of seacoasts where solid rock predominates. Rocky shores are biologically rich environments, and are a useful "natural laboratory" for studying intertidal ecology and other biological processes. Due to their high accessibility, they have been well studied for a long time and their species are well known.

<i>Postelsia</i> Species of kelp

Postelsia palmaeformis, also known as the sea palm or palm seaweed, is a species of kelp and classified within brown algae. The sea palm is found along the western coast of North America, on rocky shores with constant waves. It is one of the few algae that can survive and remain erect out of the water; in fact, it spends most of its life cycle exposed to the air. It is an annual, and edible, though harvesting of the alga is discouraged due to the species' sensitivity to overharvesting.

<i>Semibalanus balanoides</i>

Semibalanus balanoides is a common and widespread boreo-arctic species of acorn barnacle. It is common on rocks and other substrates in the intertidal zone of north-western Europe and both coasts of North America.

Davenport tide pools

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.

Starburst anemone

The sunburst anemone is a species of sea anemone in the family Actiniidae. The sunburst anemone was formerly considered the solitary form of the common aggregating anemone, but was identified as a separate species in 2000.

<i>Anthopleura xanthogrammica</i>

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

<i>Lottia digitalis</i>

Lottia digitalis common name 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 north east Pacific Ocean.

Montagus blenny

The Montagu's blenny, also known as the capuchin blenny, is a species of combtooth blenny found in the intertidal zones of the eastern Atlantic ocean from England to Madeira and the Canary Islands as well the Mediterranean Sea, the Black Sea and the Sea of Marmara. This species prefers rocky shores with much wave action. This species grows to a length of 7.6 centimetres (3.0 in) SL. It is the only species in the genus Coryphoblennius.

Marine habitats A 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.

<i>Pugettia producta</i>

Pugettia producta, known as the northern kelp crab or shield-backed kelp crab, is a species of crab in the family Epialtidae.

Reef starfish

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.

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.

Stilbaai Marine Protected Area A marine conservation area in the Western Cape in South Africa

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.


  1. 1 2 3 4 "NPCA Tide pools". NPCA. September 5, 2008. Archived from the original on September 24, 2008.
  2. Connell, Joseph H. (November 1972). "Community Interactions on Marine Rocky Intertidal Shores". Annual Review of Ecology and Systematics . 3 (1): 169–192. doi:10.1146/annurev.es.03.110172.001125. JSTOR   2096846.
  3. "Botanical Beach Tide Pools". British Columbia Parks. September 5, 2008. Archived from the original on July 24, 2008.
  4. Andy Horton (September 5, 2008). "Sea Anemones". homepages.ed.ac.uk. Archived from the original on October 17, 2008.
  5. "Snakelocks Anemone". British Marine Life Study Society. September 5, 2008. Retrieved September 6, 2008.
  6. "Biology: Regeneration". Dana Krempels, Ph.D. September 5, 2008. Archived from the original on August 6, 2009.
  7. Blanchette, Carol A. (April 1996). "Seasonal patterns of disturbance influence recruitment of the sea palm, Postelsia palmaeformis". Journal of Experimental Marine Biology and Ecology . 197 (1): 1–14. doi:10.1016/0022-0981(95)00141-7.
  8. Paine, R.T. (December 1998). "Habitat Suitability and Local Population Persistence of the Sea Palm Postelsia Palmaeformis". Ecology . 69 (6): 1787–1794. doi:10.2307/1941157. JSTOR   1941157.