Intertidal zone

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The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide: in other words, the part of the littoral zone within the tidal range. This area can include several types of habitats with various species of life, such as seastars, sea urchins, and many species of coral with regional differences in biodiversity. Sometimes it is referred to as the littoral zone or seashore , although those can be defined as a wider region.

Contents

The well-known area also includes steep rocky cliffs, sandy beaches, bogs or wetlands (e.g., vast mudflats). The area can be a narrow strip, as in Pacific islands that have only a narrow tidal range, or can include many meters of shoreline where shallow beach slopes interact with high tidal excursion. The peritidal zone is similar but somewhat wider, extending from above the highest tide level to below the lowest. Organisms in the intertidal zone are adapted to an environment of harsh extremes, living in water pressure with the potential of reaching 5,580 pounds per square inch. [1] The intertidal zone is also home to several species from different phyla (Porifera, Annelida, Coelenterata, Mollusca, Arthropoda, etc.).

Water is available regularly with the tides that can vary from brackish waters, fresh with rain, to highly saline and dry salt, with drying between tidal inundations. Wave splash can dislodge residents from the littoral zone. With the intertidal zone's high exposure to sunlight, the temperature can range from very hot with full sunshine to near freezing in colder climates. Some microclimates in the littoral zone are moderated by local features and larger plants such as mangroves. Adaptation in the littoral zone allows the use of nutrients supplied in high volume on a regular basis from the sea, which is actively moved to the zone by tides. Edges of habitats, in this case land and sea, are themselves often significant ecologies, and the littoral zone is a prime example.

A typical rocky shore can be divided into a spray zone or splash zone (also known as the supratidal zone), which is above the spring high-tide line and is covered by water only during storms, and an intertidal zone, which lies between the high and low tidal extremes. Along most shores, the intertidal zone can be clearly separated into the following subzones: high tide zone, middle tide zone, and low tide zone. The intertidal zone is one of a number of marine biomes or habitats, including estuary, neritic, surface, and deep zones.

Zonation

Tide pools at Pillar Point showing zonation on the edge of the rock ledge Tide pools at Pillar Point 7.jpg
Tide pools at Pillar Point showing zonation on the edge of the rock ledge
A rock, seen at low tide, exhibiting typical intertidal zonation, Kalaloch, Washington, western United States. Intertide zonation at Kalaloch.jpg
A rock, seen at low tide, exhibiting typical intertidal zonation, Kalaloch, Washington, western United States.

Marine biologists divide the intertidal region into three zones (low, middle, and high), based on the overall average exposure of the zone. [2] The low intertidal zone, which borders on the shallow subtidal zone, is only exposed to air at the lowest of low tides and is primarily marine in character. The mid intertidal zone is regularly exposed and submerged by average tides. The high intertidal zone is only covered by the highest of the high tides, and spends much of its time as terrestrial habitat. The high intertidal zone borders on the splash zone (the region above the highest still-tide level, but which receives wave splash). On shores exposed to heavy wave action, the intertidal zone will be influenced by waves, as the spray from breaking waves will extend the intertidal zone.

Depending on the substratum and topography of the shore, additional features may be noticed. On rocky shores, tide pools form in depressions that fill with water as the tide rises. Under certain conditions, such as those at Morecambe Bay, quicksand may form. [3]

Low tide zone (lower littoral)

This subregion is mostly submerged – it is only exposed at the point of low tide and for a longer period of time during extremely low tides. This area is teeming with life; [2] the most notable difference between this subregion and the other three is that there is much more marine vegetation, especially seaweeds. There is also a great biodiversity. Organisms in this zone generally are not well adapted to periods of dryness and temperature extremes. Some of the organisms in this area are abalone, sea anemones, brown seaweed, chitons, crabs, green algae, hydroids, isopods, limpets, mussels, nudibranchs, sculpin, sea cucumber, sea lettuce, sea palms, starfish, sea urchins, shrimp, snails, sponges, surf grass, tube worms, and whelks. Creatures in this area can grow to larger sizes because there is more available energy in the localized ecosystem. Also, marine vegetation can grow to much greater sizes than in the other three intertidal subregions due to the better water coverage. The water is shallow enough to allow plenty of sunlight to reach the vegetation to allow substantial photosynthetic activity, and the salinity is at almost normal levels. This area is also protected from large predators such as fish because of the wave action and the relatively shallow water.

Ecology

A California tide pool in the low tide zone Pteropurpura trialata is laying the eggs 1.jpg
A California tide pool in the low tide zone

The intertidal region is an important model system for the study of ecology, especially on wave-swept rocky shores. The region contains a high diversity of species, and the zonation created by the tides causes species ranges to be compressed into very narrow bands. This makes it relatively simple to study species across their entire cross-shore range, something that can be extremely difficult in, for instance, terrestrial habitats that can stretch thousands of kilometres. Communities on wave-swept shores also have high turnover due to disturbance, so it is possible to watch Ecological succession over years rather than decades.

The burrowing invertebrates that make up large portions of sandy beach ecosystems are known to travel relatively great distances in cross-shore directions as beaches change on the order of days, semilunar cycles, seasons, or years. The distribution of some species has been found to correlate strongly with geomorphic datums such as the high tide strand and the water table outcrop.

Since the foreshore is alternately covered by the sea and exposed to the air, organisms living in this environment must be adapted to both wet and dry conditions. Intertidal zone biomass reduces the risk of shoreline erosion from high intensity waves. [4] Typical inhabitants of the intertidal rocky shore include sea urchins, sea anemones, barnacles, chitons, crabs, isopods, mussels, starfish, and many marine gastropod molluscs such as limpets and whelks. Sexual and asexual reproduction varies by inhabitants of the intertidal zones. [5]

Humans have historically used intertidal zones as foraged food sources during low tide . Migratory birds also rely on intertidal species for feeding areas because of low water habitats consisting of an abundance of mollusks and other marine species. [4]

As with the dry sand part of a beach, legal and political disputes can arise over the ownership and use of the foreshore. One recent example is the New Zealand foreshore and seabed controversy. In legal discussions, the foreshore is often referred to as the wet-sand area.

For privately owned beaches in the United States, some states such as Massachusetts use the low-water mark as the dividing line between the property of the State and that of the beach owner; however the public still has fishing, fowling, and navigation rights to the zone between low and high water. Other states such as California use the high-water mark.

In the United Kingdom, the foreshore is generally deemed to be owned by the Crown, with exceptions for what are termed several fisheries, which can be historic deeds to title, dating back to King John's time or earlier, and the Udal Law, which applies generally in Orkney and Shetland.

In Greece, according to the L. 2971/01, the foreshore zone is defined as the area of the coast that might be reached by the maximum climbing of the waves on the coast (maximum wave run-up on the coast) in their maximum capacity (maximum referring to the "usually maximum winter waves" and of course not to exceptional cases, such as tsunamis). The foreshore zone, a part of the exceptions of the law, is public, and permanent constructions are not allowed on it.

In the East African and West Indian Ocean, intertidal zone management is often neglected of being a priority due to there being no intent for collective economic productivity. [6] According to workshops performing questionaries, it is stated that eighty-six percent of respondents believe mismanagement of mangrove and coastal ecosystems are due to lack of knowledge to steward the ecosystems, yet forty-four percent of respondents state that there is a fair amount of knowledge used in those regions for fisheries. [ citation needed ]

Threats

Nutrition (Eutrophic) Pollution in Assateague Island National Seashore, Maryland July 12, 2013 - Assateague Island National Seashore, Maryland (9324594954).jpg
Nutrition (Eutrophic) Pollution in Assateague Island National Seashore, Maryland

Intertidal zones are sensitive habitats with an abundance of marine species, that can experience ecological hazards associated with tourism and human-induced environmental impacts. A variety of other threats that have been summarized by scientists include nutritional pollution, over harvesting, habitat destruction, and climate change. [7] Habitat destruction is advanced through activities including harvesting fisheries with drag nets and neglect of the sensitivity of them. [8]

See also

Related Research Articles

<span class="mw-page-title-main">Coast</span> Area where land meets the sea or ocean

The coast, also known as the coastline, shoreline or seashore, is defined as the area where land meets the ocean, or as a line that forms the boundary between the land and the coastline. Shores are influenced by the topography of the surrounding landscape, as well as by water induced erosion, such as waves. The geological composition of rock and soil dictates the type of shore which is created. The Earth has around 620,000 kilometres (390,000 mi) of coastline. Coasts are important zones in natural ecosystems, often home to a wide range of biodiversity. On land, they harbor important ecosystems such as freshwater or estuarine wetlands, which are important for bird populations and other terrestrial animals. In wave-protected areas they harbor saltmarshes, mangroves or seagrasses, all of which can provide nursery habitat for finfish, shellfish, and other aquatic species. Rocky shores are usually found along exposed coasts and provide habitat for a wide range of sessile animals and various kinds of seaweeds. In physical oceanography, a shore is the wider fringe that is geologically modified by the action of the body of water past and present, while the beach is at the edge of the shore, representing the intertidal zone where there is one. Along tropical coasts with clear, nutrient-poor water, coral reefs can often be found between depths of 1–50 meters.

<span class="mw-page-title-main">Littoral zone</span> Part of a sea, lake, or river that is close to the shore

The littoral zone, also called litoral 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.

<span class="mw-page-title-main">Tide pool</span> Rocky pool on a seashore, separated from the sea at low tide, filled with seawater

A tide pool or rock pool is a shallow pool of seawater that forms on the rocky intertidal shore. These pools typically range from a few inches to a few feet deep and a few feet across. Many of these pools exist as separate bodies of water only at low tide, as seawater gets trapped when the tide recedes. Tides are caused by the gravitational pull of the sun and moon. A tidal cycle is usually about 25 hours and consists of one or two high tides and two low tides.

<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

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.

<span class="mw-page-title-main">Marine ecosystem</span> Ecosystem in saltwater environment

Marine ecosystems are the largest of Earth's aquatic ecosystems and exist in waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the surface of the Earth and account for more than 97% of Earth's water supply and 90% of habitable space on Earth. Seawater has an average salinity of 35 parts per thousand of water. Actual salinity varies among different marine ecosystems. Marine ecosystems can be divided into many zones depending upon water depth and shoreline features. The oceanic zone is the vast open part of the ocean where animals such as whales, sharks, and tuna live. The benthic zone consists of substrates below water where many invertebrates live. The intertidal zone is the area between high and low tides. Other near-shore (neritic) zones can include mudflats, seagrass meadows, mangroves, rocky intertidal systems, salt marshes, coral reefs, lagoons. In the deep water, hydrothermal vents may occur where chemosynthetic sulfur bacteria form the base of the food web.

<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. It is the only known species in the genus Postelsia. 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.

<span class="mw-page-title-main">Wrack zone</span> Coastal area where organic material is deposited at high tide

The wrack zone or wrack line is a coastal feature where organic material and other debris are deposited at high tide. This zone acts as a natural input of marine resources into a terrestrial system, providing food and habitat for a variety of coastal organisms.

<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.

<span class="mw-page-title-main">Seashore wildlife</span>

Seashore wildlife habitats exist from the Tropics to the Arctic and Antarctic. Seashores and beaches provide varied habitats in different parts of the world, and even within the same beach. Phytoplankton is at the bottom of some food chains, while zooplankton and other organisms eat phytoplankton. Kelp is also autotrophic and at the bottom of many food chains. Coastal areas are stressed through rapid changes, for example due to tides.

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

Lottia gigantea, common name the owl limpet, is a species of sea snail, a true limpet, a marine gastropod mollusc in the family Lottiidae. Its genome has been sequenced at the Joint Genome Institute.

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

Lottia digitalis, commonly known as 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-eastern Pacific Ocean.

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

Lottia scabra or the rough limpet is a species of sea snail, a true limpet, a marine gastropod mollusk in the family Lottiidae.

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

A marine habitat is a habitat that supports 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>Sicyases sanguineus</i> Species of fish

Sicyases sanguineus is a species of amphibious marine clingfish in the family Gobiesocidae. It lives in the Southeast Pacific along the entire coast of Chile and southern Peru.

<span class="mw-page-title-main">Flat coast</span> Shoreline where the land descends gradually into the sea

At a flat coast or flat shoreline, the land descends gradually into the sea. Flat coasts can be formed either as a result of the sea advancing into gently sloping terrain or through the abrasion of loose rock. They may be basically divided into two parallel strips: the shoreface and the beach.

<span class="mw-page-title-main">Dana Point State Marine Conservation Area</span> Marine protected area off the coast of Orange County, CA

Dana Point State Marine Conservation Area (SMCA) is one of four adjoining marine protected areas off the coast of Orange County, CA, on California’s South Coast. By itself, the SMCA measures 3.45 square miles. The SMCA protects marine life by limiting the removal of marine wildlife from within its borders, including tide pools. Dana Point SMCA prohibits take of living marine resources except: only the following species may be taken recreationally below the mean lower low tide line only: finfish by hook-and-line or by spearfishing, and lobster and sea urchin. The commercial take of coastal pelagic species by round haul net, and spiny lobster and sea urchin only is allowed.

The Helderberg Marine Protected Area is a small marine conservation area on the north-eastern side of False Bay in the Western Cape province of South Africa, It lies between the mouths of the Lourens River in the Strand, and the Eerste River in Macassar.

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.

The Sardinia Bay Marine Protected Area is an inshore conservation region in the territorial waters of the Eastern Cape province, South Africa

References

  1. US Department of Commerce, National Oceanic and Atmospheric Administration. "What is the intertidal zone?". oceanservice.noaa.gov. Retrieved 2022-11-29.
  2. 1 2 "What is the Intertidal Zone?". WorldAtlas. 10 January 2018. Retrieved 2019-09-17.
  3. "Why is Morecambe Bay so dangerous?". The Guardian. 2004-02-12.
  4. 1 2 "Intertidal Zone". National Geographic Society. 2019-10-10. Retrieved 2022-04-06.
  5. "Intertidal Ecology" (PDF). USF College of Marine Science. 2002. Retrieved 31 May 2023.
  6. Nordlund, Lina Mtwana; de la Torre-Castro, Maricela; Erlandsson, Johan; et al. (2013-12-28). "Intertidal Zone Management in the Western Indian Ocean: Assessing Current Status and Future Possibilities Using Expert Opinions". Ambio. 43 (8): 1006–1019. doi:10.1007/s13280-013-0465-8. ISSN   0044-7447. PMC   4235897 . PMID   24375399.
  7. "Climate Change Impacts on Intertidal Zone Populations". NCCOS Coastal Science Website. Retrieved 2022-04-03.
  8. Nordlund, Lina Mtwana; de la Torre-Castro, Maricela; Erlandsson, Johan; Conand, Chantal; Muthiga, Nyawira; Jiddawi, Narriman; Gullström, Martin (December 2014). "Intertidal Zone Management in the Western Indian Ocean: Assessing Current Status and Future Possibilities Using Expert Opinions". Ambio. 43 (8): 1006–1019. Bibcode:2014Ambio..43.1006N. doi:10.1007/s13280-013-0465-8. ISSN   0044-7447. PMC   4235897 . PMID   24375399.