The wrack zone or wrack line is a coastal feature where organic material (e.g. kelp, seagrass, driftwood) 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.
The wrack zone is most commonly associated with a sandy beach habitat but can also be present in rocky shores, mangroves, salt marshes, and other coastal systems. [1] Debris is carried up the intertidal zone as the tide comes in, and is deposited on the sand when the tide goes out. The zone can be recognized as a linear patch of debris toward the upper part of a beach running parallel to the water's edge. The location of the wrack zone varies geographically and temporally. It is found at a higher elevation during spring tides compared to neap tides. The size of a beach and its intertidal zone will influence the location of wrack deposition. Additionally, storms will often increase the volume of debris that is deposited.
The wrack zone may be composed of a variety of materials, both organic and inorganic. A common organic component is seaweed, such as kelp, which easily floats to coastal waters after being dislodged by its holdfast or otherwise torn by wave action and animal activity. Other organic components may include seagrasses, terrestrial plants, driftwood, and stranded animal remains. Common inorganic components include plastics, fishing line, and other manmade materials.
Organic debris that accumulates in the wrack zone is considered a cross-boundary subsidy, linking the marine system to the terrestrial system by providing resources that form the base of coastal food webs. [2] Terrestrial invertebrates such as isopods, amphipods, polychaetes, and shore flies feed on seaweed and other dead material. [3] These invertebrates provide food for shore birds and other predators on the beach. In addition, when organic debris decomposes, it delivers nutrients to the soil, promoting the growth of coastal vegetation. [1]
The wrack zone adds structure to the beach landscape, providing habitat for animals that live there. For example, rove beetles burrow in the wet sand below the wrack zone, benefiting from moist conditions and the availability of herbivorous invertebrate prey species. [3] Kelp flies like Coelopa pilipes rely on washed up kelp in wrack zones for food, shelter, and oviposition. Additionally, the wrack zone plays a role in the formation of dunes by promoting the accumulation of wind-blown sand. [4]
Manmade objects are often washed ashore in the wrack zone, posing a threat to coastal animals. Plastics in particular are the most common form of litter found on beaches, [5] and it is estimated that 46% of shorebirds ingest plastic in their lifetime while 26% experience entanglement. [6] A variety of effects have been observed in animals that ingest plastic, including reduced reproductive success, changes in immune function, and increased mortality. [6] There is also growing evidence suggesting that plastic bioaccumulates through the food web, so predators may be affected by the accumulation of plastic in their prey's diet. [6]
Sandy beaches are often groomed for aesthetic and recreational value. The removal of organic debris limits habitat and food availability for wrack-associated animals and inhibits the formation of dunes, although the deleterious effects are ameliorated by the removal of plastics and the like. [4]
Sea walls and other coastal armoring structures can affect the location of a wrack zone and reduce the accumulation of organic material. [1] This can negatively affect the structure and diversity of coastal habitats.
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.
Marine biology is the scientific study of the biology 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.
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.
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.
Marine debris, also known as marine litter, is human-created solid material that has deliberately or accidentally been released in a sea or ocean. Floating oceanic debris tends to accumulate at the center of gyres and on coastlines, frequently washing aground, when it is known as beach litter or tidewrack. Deliberate disposal of wastes at sea is called ocean dumping. Naturally occurring debris, such as driftwood and drift seeds, are also present. With the increasing use of plastic, human influence has become an issue as many types of (petrochemical) plastics do not biodegrade quickly, as would natural or organic materials. The largest single type of plastic pollution (~10%) and majority of large plastic in the oceans is discarded and lost nets from the fishing industry. Waterborne plastic poses a serious threat to fish, seabirds, marine reptiles, and marine mammals, as well as to boats and coasts.
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.
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.
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.
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.
The Seal Beach National Wildlife Refuge is a wildlife refuge encompassing 965 acres (3.91 km2) located in the California coastal community of Seal Beach. Although it is located in Orange County it is included as part of the San Diego National Wildlife Refuge Complex. It was established in 1972.
A wild fishery is a natural body of water with a sizeable free-ranging fish or other aquatic animal population that can be harvested for its commercial value. Wild fisheries can be marine (saltwater) or lacustrine/riverine (freshwater), and rely heavily on the carrying capacity of the local aquatic ecosystem.
Sea foam, ocean foam, beach foam, or spume is a type of foam created by the agitation of seawater, particularly when it contains higher concentrations of dissolved organic matter derived from sources such as the offshore breakdown of algal blooms. These compounds can act as surfactants or foaming agents. As the seawater is churned by breaking waves in the surf zone adjacent to the shore, the surfactants under these turbulent conditions trap air, forming persistent bubbles that stick to each other through surface tension.
Ocypode gaudichaudii, also known as the painted ghost crab or cart driver crab, is a species of crab found on Pacific beaches from El Salvador to Chile as well as on the Galápagos Islands. The species was first described by Henri Milne-Edwards and Hippolyte Lucas in 1843.
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.
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 Hluleka Marine Protected Area is an inshore conservation region in the territorial waters of the Eastern Cape province of 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.
Beach cleaning or clean-up is the process of removing solid litter, dense chemicals, and organic debris deposited on a beach or coastline by the tide, local visitors, or tourists. Humans pollute beaches with materials such as plastic bottles and bags, plastic straws, fishing gear, cigarette filters, six-pack rings, surgical masks and many other items that often lead to environmental degradation. Every year hundreds of thousands of volunteers comb beaches and coastlines around the world to clean this debris. These materials are also called “marine debris” or "marine pollution" and their quantity has been increasing due to anthropocentric activities.
The Rocherpan Marine Protected Area is a small coastal conservation region on the West Coast of the Western Cape province, in the territorial waters of South Africa. It is about 25 km north of Velddrif on the road to Elands Bay, north of Dwarskersbos.
The Sixteen Mile Beach Marine Protected Area is a coastal conservation region in the territorial waters of South Africa, near Saldanha Bay on the Western Cape coast. The MPA is part of the West Coast National Park which is the core component of the Cape West Coast Biosphere Reserve. The beach stretches from Yzerfontein's Main Beach to the start of the West Coast National Park.
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