Littoral zone

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.

The term has no single definition. What is regarded as the full extent of the littoral zone, and the way the littoral zone is divided into subregions, varies in different contexts. (Lakes and rivers have their own definitions.) The use of the term also varies from one part of the world to another, and between different disciplines. For example, military commanders speak of the littoral in ways that are quite different from marine biologists.

The adjacency of water gives a number of distinctive characteristics to littoral regions. The erosive power of water results in particular types of landforms, such as sand dunes, and estuaries. The natural movement of the littoral along the coast is called the littoral drift. Biologically, the ready availability of water enables a greater variety of plant and animal life, and particularly the formation of extensive wetlands. In addition, the additional local humidity due to evaporation usually creates a microclimate supporting unique types of organisms.

The word littoral may be used both as a noun and as an adjective. It derives from the Latin noun litus, litoris, meaning "shore". (The doubled tt is a late-medieval innovation, and the word is sometimes seen in the more classical-looking spelling litoral.)

In oceanography and marine biology

Olympic Coast National Marine Sanctuary
The littoral zone of an ocean is the area close to the shore and extending out to the edge of the continental shelf.
Portugal 20040711 027
The intertidal zone of a beach is also part of the littoral zone.
Klamath river estuary
Estuaries are also in the littoral zone.

In oceanography and marine biology, the idea of the littoral zone is extended roughly to the edge of the continental shelf. Starting from the shoreline, the littoral zone begins at the spray region just above the high tide mark. From here, it moves to the intertidal region between the high and low water marks, and then out as far as the edge of the continental shelf. These three subregions are called, in order, the supralittoral zone, the eulittoral zone and the sublittoral zone.

Supralittoral zone

The supralittoral zone (also called the splash, spray or supratidal zone) is the area above the spring high tide line that is regularly splashed, but not submerged by ocean water. Seawater penetrates these elevated areas only during storms with high tides. Organisms here must cope also with exposure to fresh water from rain, cold, heat and predation by land animals and seabirds. At the top of this area, patches of dark lichens can appear as crusts on rocks. Some types of periwinkles, Neritidae and detritus feeding Isopoda commonly inhabit the lower supralittoral.[1]

Eulittoral zone

The eulittoral zone (also called the midlittoral or mediolittoral zone) is the intertidal zone also known as the foreshore. It extends from the spring high tide line, which is rarely inundated, to the spring low tide line, which is rarely not inundated. The wave action and turbulence of recurring tides shapes and reforms cliffs, gaps, and caves, offering a huge range of habitats for sedentary organisms. Protected rocky shorelines usually show a narrow almost homogenous eulittoral strip, often marked by the presence of barnacles. Exposed sites show a wider extension and are often divided into further zones. For more on this, see intertidal ecology.

Sublittoral zone

The sublittoral zone starts immediately below the eulittoral zone. This zone is permanently covered with seawater and is approximately equivalent to the neritic zone.

In physical oceanography, the sublittoral zone refers to coastal regions with significant tidal flows and energy dissipation, including non-linear flows, internal waves, river outflows and oceanic fronts. In practice, this typically extends to the edge of the continental shelf, with depths around 200 meters.

In marine biology, the sublittoral refers to the areas where sunlight reaches the ocean floor, that is, where the water is never so deep as to take it out of the photic zone. This results in high primary production and makes the sublittoral zone the location of the majority of sea life. As in physical oceanography, this zone typically extends to the edge of the continental shelf. The benthic zone in the sublittoral is much more stable than in the intertidal zone; temperature, water pressure, and the amount of sunlight remain fairly constant. Sublittoral corals do not have to deal with as much change as intertidal corals. Corals can live in both zones, but they are more common in the sublittoral zone.

Within the sublittoral, marine biologists also identify the following:

  • The infralittoral zone is the algal dominated zone to maybe five metres below the low water mark.
  • The circalittoral zone is the region beyond the infralittoral, that is, below the algal zone and dominated by sessile animals such as mussels and oysters.

Shallower regions of the sublittoral zone, extending not far from the shore, are sometimes referred to as the subtidal zone.

In freshwater ecosystems

Moon Lake shoreline - Riding Mountain National Park
Shoreline of a lake with nearly unvegetated littoral zone

In freshwater situations, littoral zones occur on the edge of large lakes and rivers, often with extensive areas of wetland. Hence, they are sometimes referred to as fringing wetlands. Here, the effects of tides are minimal, so other definitions of "littoral" are used. For example, the Minnesota Department of Natural Resources defines littoral as that portion of the lake that is less than 15 feet in depth.[2]

The littoral zone may form a narrow or broad fringing wetland, with extensive areas of aquatic plants sorted by their tolerance to different water depths. Typically, four zones are recognized, from higher to lower on the shore: wooded wetland, wet meadow, marsh and aquatic vegetation.[3] The relative areas of these four types depends not only on the profile of the shoreline, but upon past water levels. The area of wet meadow is particularly dependent upon past water levels;[4] in general, the area of wet meadows along lakes and rivers increases with natural water level fluctuations.[5][6] Many of the animals in lakes and rivers are dependent upon the wetlands of littoral zones, since the rooted plants provide habitat and food. Hence, a large and productive littoral zone is considered an important characteristic of a healthy lake or river.[4]

Littoral zones are at particular risk for two reasons. First, human settlement is often attracted to shorelines, and settlement often disrupts breeding habitats for littoral zone species. For example, many turtles are killed on roads when they leave the water to lay their eggs in upland sites. Fish can be negatively affected by docks and retaining walls which remove breeding habitat in shallow water. Some shoreline communities even deliberately try to remove wetlands since they may interfere with activities like swimming. Overall, the presence of human settlement has a demonstrated negative impact upon adjoining wetlands.[7] An equally serious problem is the tendency to stabilize lake or river levels with dams. Dams removed the spring flood which carries nutrients into littoral zones, and reduces the natural fluctuation of water levels upon which many wetland plants and animals depend.[8][9] Hence, over time, dams can reduce the area of wetland from a broad littoral zone to a narrow band of vegetation. Marshes and wet meadows are at particular risk.

Other definitions

For the purposes of naval operations, the United States Navy divides the littoral zone in the ways shown on the diagram at the top of this article. The United States Army Corps of Engineers and Environmental Protection Agency have their own definitions, and these have legal implications.

See also

Notes

  1. ^ Yip and Madl
  2. ^ "Fisheries lake surveys". Minnesota Department of Natural Resources.
  3. ^ Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. Chapter 2.
  4. ^ a b Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK.
  5. ^ Wilcox, D.A, Thompson, T.A., Booth, R.K. and Nicholas, J.R. 2007. Lake-level variability and water availability in the Great Lakes. USGS Circular 1311. 25 p.
  6. ^ Hughes, F.M.R. (ed.). 2003. The Flooded Forest: Guidance for policy makers and river managers in Europe on the restoration of floodplain forests. FLOBAR2, Department of Geography, University of Cambridge, Cambridge, UK. 96 p.
  7. ^ Houlahan, J. E.; Keddy, P. A.; Makkay, K.; Findlay, C. S. (2006). "The effects of adjacent land use on wetland species richness and community composition". Wetlands. 26 (1): 79–96. doi:10.1672/0277-5212(2006)26[79:TEOALU]2.0.CO;2.
  8. ^ Middleton, B. A. (ed.) 2002. Flood Pulsing in Wetlands: Restoring the Natural Hydrological Balance. John Wiley, New York
  9. ^ Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497. Chapter 2.

References

Aquatic ecosystem

An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.

Ballantine scale

The Ballantine scale is a biologically defined scale for measuring the degree of exposure level of wave action on a rocky shore. Devised in 1961 by W. J. Ballantine, then at the zoology department of Queen Mary College, London, the scale is based on the observation that where shoreline species are concerned "Different species growing on rocky shores require different degrees of protection from certain aspects of the physical environment, of which wave action is often the most important." The species present in the littoral zone therefore indicate the degree of the shore's exposure.

Black Sea Biosphere Reserve

The Black Sea Biosphere Reserve (Ukrainian: Чорноморський біосферний заповідник) is a biosphere reserve of Ukraine that is located at littoral zone of the northern Black Sea coast covering regions of the Kherson and Mykolaiv Oblasts and including Gulf of Tendra and Yahorlyk Bay. The reserve is part of the National Academy of Sciences of Ukraine.

Cancer (genus)

For other uses, see Cancer (disambiguation).

Cancer is a genus of marine crabs in the family Cancridae. It includes eight extant species and three extinct species, including familiar crabs of the littoral zone, such as the European edible crab (Cancer pagurus), the Jonah crab (Cancer borealis) and the red rock crab (Cancer productus). It is thought to have evolved from related genera in the Pacific Ocean in the Miocene.

Hexagrammidae

The family of marine fishes Hexagrammidae incorporates the greenlings. These fish are found on the continental shelf in the temperate or subarctic waters of the North Pacific. They are a well-known family in the littoral zone from southern California north to the Aleutian Islands. The most commercially important species is the lingcod (Ophiodon elongatus), a common food fish.

Most hexagrammids are small to moderate in size, averaging around 50 cm, although the lingcod can be much larger. Like many other scorpaeniform species, they have broad, spiny pectoral, dorsal, and anal fins. They are scavengers but also catch and eat small fish and bottom-dwelling animals such as crabs. They can be found off rocky shorelines, in kelp beds, and, especially during spawning, in shallow inlets and tidepools.

The kelp greenling (Hexagrammos decagrammus) is a popular sport fish, and although it is not commercially valuable, it is considered a delicious food catch. The lingcod is long and olive-yellow in color, and has a very large, toothy mouth. The painted greenling (Oxylebius pictus) is smaller, brighter in color, and easily recognized by its large vertical red bands.

Intertidal zone

The intertidal zone, also known as the foreshore or seashore, is the area that is 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, such as starfish, 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.

The well-known area also includes steep rocky cliffs, sandy beaches, 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. 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, but varies from 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 ameliorated 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.

Limnetic zone

The limnetic zone is the open and well-lit area of a freestanding body of fresh water, such as a lake or pond. Not included in this area is the littoral zone, which is the shallow, near-shore area of the water body. Together, these two zones comprise the photic zone.

There are two main sources of oxygen to the photic zone: atmospheric mixing and photosynthesis. Unlike the profundal zone, the limnetic zone is the layer that receives sufficient sunlight, allowing for photosynthesis. For this reason, it is often simply referred to as the photic zone. The limnetic zone is the most photosynthetically-active zone of a lake since it is the primary habitat for planktonic species. Because phytoplankton populations are densest here, it is the zone most heavily responsible for oxygen production within the aquatic ecosystem.Limnetic communities are quite complex. Zooplankton populations often consist of copepods, cladocerans, and rotifers occurring in the open water of lakes. Most limnetic communities will consist of one dominant species of copepod, one dominant cladoceran, and one dominant rotifer. Zooplankters are able to move more freely through the limnetic zone than in the littoral zone, both vertically and horizontally. This is because the bottom of a lake is richer in debris and substrates that provide habitat niches. A limnetic zooplankton population will usually consist of two to four species, each in a different genus.In addition to zooplankton, organisms in the limnetic zone include insects and fish. Many species of freshwater fish live in the limnetic zone because of the abundance of food, though these species often transition to the littoral zone as well.

Littoral (military)

In military and naval warfare, littoral combat is operations in and around the littoral zone, within a certain distance of shore, including surveillance, mine-clearing and support for landing operations and other types of combat shifting from water to ground, and back.

The Littoral combat ship is being developed in a current U.S. Navy program to improve force maneuverability as well as to provide a platform for the deployment of small unmanned systems in littoral operations.

Marine botany

Marine botany is the study of aquatic plants and algae that live in seawater of the open ocean and the littoral zone, along shorelines of the intertidal zone, and in brackish water of estuaries.

It is a branch of marine biology and botany.

Operational Zone of the Adriatic Littoral

The Operational Zone of the Adriatic Littoral (German: Operationszone Adriatisches Küstenland, OZAK; or colloquially: Operationszone Adria); Italian: Zona d'operazioni del Litorale adriatico; Croatian: Operativna zona Jadransko primorje; Slovene: Operacijska zona Jadransko primorje) was a Nazi German district on the northern Adriatic coast created during World War II in 1943. It was formed out of territories that were previously under Fascist Italian control until its takeover by Germany. It included parts of present-day Italian, Slovenian, and Croatian territories. The area was administered as territory attached, but not incorporated to, the Reichsgau of Carinthia. The capital of the zone was the city of Trieste.

Padina pavonica

Padina pavonica, commonly known as the peacock's tail, is a small brown alga found in the Indian Ocean, the Pacific Ocean, the Atlantic Ocean and the Mediterranean Sea. It inhabits pools in the littoral zone typically with clayey, silty or sandy sediments. Other habitats include rocks and shell fragments in the shallow sublittoral, seagrass meadows, mangrove roots and coral reefs on tidal flats

Planaxidae

Planaxidae, common name planaxids or clusterwinks, are a taxonomic family of small and minute sea snails, pantropical marine gastropod molluscs in the superfamily Cerithoidea. They are found on rocky shores in the littoral zone of the tropics and subtropics.

Profundal zone

The profundal zone is a deep zone of an inland body of freestanding water, such as a lake or pond, located below the range of effective light penetration. This is typically below the thermocline, the vertical zone in the water through which temperature drops rapidly. The temperature difference may be large enough to hamper mixing with the littoral zone in some seasons which causes a decrease in oxygen concentrations. The profundal is often defined, in accordance with Thienemann (1925), as the deepest, vegetation-free, and muddy zone of the lacustrine benthal. The profundal zone is often part of the aphotic zone.

The lack of light and oxygen in the profundal zone determines the type of biological community that can live in this region and this is distinctly different from the community in the overlying waters. The profundal macrofauna is therefore characterized by physiological and behavioural adaptations to low oxygen concentration. Chironomidae and Oligochaetae often dominate the benthic fauna of the profundal zone because they possess hemoglobin like molecules to extract oxygen from poorly oxygenated water.

Rocky shore

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.

Scandinavian Brazilians

Scandinavian Brazilians (Portuguese: escandinavo-brasileiro) refers to Brazilians of full or partial Scandinavian ancestry, or Scandinavian-born people residing in Brazil.

The Scandinavian settlement in Brazil began in the mid to late 19th century and was predominant when Scandinavian peoples arrived in Brazil. Many Scandinavians came to Brazil for economic reasons and to start a new life.In recent years, many Norwegians and Swedes have migrated to the littoral zone of the State of Rio Grande do Norte (mainly Natal) and Ceará, attracted by the beaches and the tropical climate.

Surf zone

As ocean surface waves come closer to shore they break, forming the foamy, bubbly surface called surf. The region of breaking waves defines the surf zone. After breaking in the surf zone, the waves (now reduced in height) continue to move in, and they run up onto the sloping front of the beach, forming an uprush of water called swash. The water then runs back again as backswash. The nearshore zone where wave water comes onto the beach is the surf zone. The water in the surf zone, or breaker zone, is shallow, usually between 5 and 10 m (16 and 33 ft) deep; this causes the waves to be unstable.

Water beetle

A water beetle is a generalized name for any beetle that is adapted to living in water at any point in its life cycle. Most water beetles can only live in fresh water, with a few marine species that live in the intertidal zone or littoral zone. There are approximately 2000 species of true water beetles native to lands throughout the world.Many water beetles carry an air bubble, called the elytra cavity, underneath their abdomens, which provides an air supply, and prevents water from getting into the spiracles. Others have the surface of their exoskeleton modified to form a plastron, or "physical gill", which permits direct gas exchange with the water. Some families of water beetles have fringed hind legs adapted for swimming, but most do not. Most families of water beetles have larvae that are also aquatic; many have aquatic larvae and terrestrial adults.

Woodlouse

A woodlouse (plural woodlice) is a crustacean from the monophyletic suborder Oniscidea within the isopods. The first woodlice were marine isopods which are presumed to have colonised land in the Carboniferous. They have many common names and although often referred to as 'terrestrial Isopods' some species live semiterrestrially or have recolonised aquatic environments. Woodlice in the families Armadillidae, Armadillidiidae, Eubelidae, Tylidae and some other genera can roll up into an almost perfect sphere as a defensive mechanism, others have partial rolling ability but most cannot conglobate at all.

Woodlice have a basic morphology of a segmented, dorso-ventrally flattened body with 7 pairs of jointed legs, specialised appendages for respiration and like other peracarids, females carry fertilised eggs in their marsupium, through which they provide developing embryos with water, oxygen and nutrients. The immature young hatch as mancae and receive further maternal care in some species. Juveniles then go through a series of moults before reaching maturity.

While the broader phylogeny of the Oniscideans has not been settled, five Infraorders/Sections are agreed on with 3637 species validated in scientific literature in 2004 and 3710 species in 2014 out of an estimated total of 5000-7000 species extant worldwide. Key adaptations to terrestrial life has led to a highly diverse set of animals; from the marine littoral zone and subterranean lakes to arid deserts and mountain slopes 4,725m above sea-level, woodlice have established themselves in most terrestrial biomes and represent the full range of transitional forms and behaviours for living on land.

Woodlice are widely studied in the contexts of evolutionary biology, behavioural ecology and nutrient cycling. They are popular as terrarium pets because of their varied colour and texture forms, conglobating ability and ease of care.

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