The intertidal zone, also known as the foreshore, is the area above
water level at low
tide and
underwater at high tide (in other words, the area within the
tidal range). This area can include several types of
habitats with various species of
life
Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from that which does not, and is defined by the capacity for growth, reaction to stimuli, metabolism, energy ...
, such as
seastars,
sea urchins
Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of ...
, 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.
The well-known area also includes steep rocky
cliffs
In geography and geology, a cliff is an area of rock which has a general angle defined by the vertical, or nearly vertical. Cliffs are formed by the processes of weathering and erosion, with the effect of gravity. Cliffs are common on coa ...
, sandy
beaches
A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc shells ...
,
bogs
A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and muskeg; a ...
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. The intertidal zone is also home to several species from different
phyla Phyla, the plural of ''phylum'', may refer to:
* Phylum, a biological taxon between Kingdom and Class
* by analogy, in linguistics, a large division of possibly related languages, or a major language family which is not subordinate to another
Phy ...
(
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
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excr ...
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
Marine biologists divide the intertidal region into three zones (low, middle, and high), based on the overall average exposure of the zone.
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
In offshore construction, the splash zone is the transition from air to water when lowering heavy burdens into the sea. The overall efforts applied on the crane change dramatically when the load starts touching water, up to the point where it is ...
(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
Morecambe Bay is a large estuary in northwest England, just to the south of the Lake District National Park. It is the largest expanse of intertidal mudflats and sand in the United Kingdom, covering a total area of . In 1974, the second largest ...
,
quicksand may form.
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;
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
The sea lettuces comprise the genus ''Ulva'', a group of edible green algae that is widely distributed along the coasts of the world's oceans. The type species within the genus ''Ulva'' is ''Ulva lactuca'', wikt:lactuca, ''lactuca'' being Latin ...
,
sea palms,
starfish,
sea urchins,
shrimp,
snails,
sponge
Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate throu ...
s,
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
The intertidal region is an important model system for the study of
ecology
Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overl ...
, 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 have adaptions for both wet and dry conditions. Intertidal zone biomass does reduce the risk of shoreline
erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is d ...
from high intensity waves. Typical inhabitants of the intertidal rocky shore include
urchins,
sea anemones,
barnacles
A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosiv ...
,
chitons, crabs,
isopods, mussels,
starfish, and many marine
gastropod molluscs such as
limpets and
whelks
Whelk (also known as scungilli) is a common name applied to various kinds of sea snail. Although a number of whelks are relatively large and are in the family Buccinidae (the true whelks), the word ''whelk'' is also applied to some other marine ...
. Sexual and asexual reproduction varies by inhabitants of the intertidal zones.
Sea anemones are one of the only species that can perform sexual and
asexual reproduction in intertidal zone
.
Humans have historically used intertidal zones as foraged food sources during low ti
.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.
Legal issues
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
The New Zealand foreshore and seabed controversy is a debate in the politics of New Zealand. It concerns the ownership of the country's foreshore and seabed, with many Māori groups claiming that Māori have a rightful claim to title. These ...
. 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
Massachusetts (Massachusett: ''Muhsachuweesut Massachusett_writing_systems.html" ;"title="nowiki/> məhswatʃəwiːsət.html" ;"title="Massachusett writing systems">məhswatʃəwiːsət">Massachusett writing systems">məhswatʃəwiːsət'' En ...
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 although there are notable exceptions, especially 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
Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders wi ...
, 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 etc.). The foreshore zone, a part of the exceptions of the law, is public, and permanent constructions are not allowed on it.
In the
East Africa and West Indian Ocean, intertidal zone management is often neglected of being a priority due to there being no intent for collective economic productivit
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.
Threats
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. Habitat destruction is advanced through activities including harvesting fisheries with drag nets and neglect of the sensitivity of them.
In popular culture
''The Intertidal Zone'' was used as a title for a comic book written by
Stephen Hillenburg. The comic strip starred "Bob The Sponge", an early predecessor of
SpongeBob SquarePants.
Gallery
Image:CornishMussels.JPG, Mussels in the intertidal zone in Cornwall, England.
Image:CornishBarnacles.JPG, Barnacles
A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosiv ...
and limpets in the intertidal zone near Newquay, Cornwall, England.
Image:Micro-climate on rock at Sunrise-on- Sea.jpg, A tidal pool in the intertidal zone during low tide, Sunrise-on-Sea, South Africa
South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...
.
Image:Life around stone at Sunrise-on-Sea.jpg, Unexplained crumbs of sand that appear to have been deposited around stone by escaping air.
Image: Mussels Dalian.JPG, Rocks in intertidal zone completely covered by mussels, at Bangchuidao Scenic Area, Dalian, Liaoning Province, China.
See also
*
Ballantine Scale
*
Ecological forecasting
*
Littoral series
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 t ...
*
NaGISA
NaGISA (Natural Geography in Shore Areas or Natural Geography of In-Shore Areas) is an international collaborative effort aimed at inventorying, cataloguing, and monitoring biodiversity of the in-shore area. So named for the Japanese word "nagisa ...
*
Shorezone
ShoreZone is a mapping program that uses oblique aerial images acquired at low altitude, and during the lowest daylight tides of the year, to inventory alongshore and across-shore geomorphological and biological features of the Pacific Northwest i ...
References
External links
Enchanted LearningEncyclopædia BritannicaWatch the online documentary ''The Intertidal Zone''
{{Biomes
Aquatic ecology
Tides
Marine biology
Habitats
Coastal geography
Coastal and oceanic landforms
Fisheries science
Physical oceanography
Oceanographical terminology
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