The San Diego Formation is a geological formation in southwestern San Diego County, California , United States, and northwestern Baja California , Mexico.
118-717: It is a coastal transitional marine and non-marine pebble and cobble conglomerate deposit and marine sandstone rock with marine fossils, from a former bay, deposited during the Middle Pliocene to Late Pliocene ages (2–3 million years ago), of the Pliocene period during the Cenozoic Era . This formation is found from the south side of Mount Soledad in San Diego County to Rosarito Beach in northern Baja California , including Tijuana , Mexico, and
236-494: A " keystone species " in the Arctic marine regions. The walrus has played a prominent role in the cultures of many indigenous Arctic peoples , who have hunted it for meat, fat, skin, tusks, and bone. During the 19th century and the early 20th century, walrus were widely hunted for their blubber , walrus ivory , and meat. The population of walruses dropped rapidly all around the Arctic region. It has rebounded somewhat since, though
354-442: A diverse and opportunistic diet, feeding on more than 60 genera of marine organisms, including shrimp , crabs, priapulids , spoon worms , tube worms , soft corals , tunicates , sea cucumbers , various mollusks (such as snails , octopuses , and squid ), some types of slow-moving fish , and even parts of other pinnipeds. However, it prefers benthic bivalve mollusks , especially clams , for which it forages by grazing along
472-518: A large number of organisms and support very high productivity. Estuaries provide habitats for salmon and sea trout nurseries, as well as migratory bird populations. Two of the main characteristics of estuarine life are the variability in salinity and sedimentation . Many species of fish and invertebrates have various methods to control or conform to the shifts in salt concentrations and are termed osmoconformers and osmoregulators . Many animals also burrow to avoid predation and to live in
590-411: A mutually beneficial relationship with mangrove forests at high tide level and sea grass meadows in between: the reefs protect the mangroves and seagrass from strong currents and waves that would damage them or erode the sediments in which they are rooted, while the mangroves and seagrass protect the coral from large influxes of silt , fresh water and pollutants . This additional level of variety in
708-578: A peak in the 1970s-1980s, but subsequently, walrus numbers have again declined. Early aerial censuses of Pacific walrus conducted at five-year intervals between 1975 and 1985 estimated populations of above 220,000 in each of the three surveys. In 2006, the population of the Pacific walrus was estimated to be around 129,000 on the basis of an aerial census combined with satellite tracking. There were roughly 200,000 Pacific walruses in 1990. The much smaller population of Atlantic walruses ranges from
826-575: A primary concern regarding water quality. To avoid intrusion, the Sweetwater Authority constantly monitors the basin water levels, which have remained stable since the 1980s. A factor that contributes to limit the groundwater pumping is the importation of Colorado River water. However, to reduce demands for imported water, desalination plants have been installed. The Richard A. Reynolds Groundwater Desalination Facility, in Chula Vista,
944-404: A regional effort to reduce demands for imported water. Besides those of clams and other mollusks , quite a few bird fossils (which are generally rare) have been found in this geological formation . Among them is a possible ancestor of Cassin's auklet ( Ptychoramphus aleuticus ) and the loons Gavia concinna and G. howardae . The former was quite likely a close relative or even ancestor of
1062-468: A relative of humpback whale . Parapontoporia P. sternbergi A close relative of the baiji . Semirostrum S. ceruttii A porpoise with a lower jaw extended few inches beyond the upper jaw (similar to a halfbeak ). Callorhinus C. gilmorei A relative of the northern fur seal . Dusignathus D. seftoni A walrus . Valenictus V. chulavistensis A walrus. Hydrodamalis H. cuestae A close relative of
1180-476: A result, estuaries are suffering degradation by many factors, including sedimentation from soil erosion from deforestation; overgrazing and other poor farming practices; overfishing; drainage and filling of wetlands; eutrophication due to excessive nutrients from sewage and animal wastes; pollutants including heavy metals, PCBs, radionuclides and hydrocarbons from sewage inputs; and diking or damming for flood control or water diversion. Estuaries provide habitats for
1298-556: A significant portion (about 42%) of struck and lost animals. Several hundred are removed annually around Greenland. The sustainability of these levels of harvest is difficult to determine given uncertain population estimates and parameters such as fecundity and mortality . The Boone and Crockett Big Game Record book has entries for Atlantic and Pacific walrus. The recorded largest tusks are just over 30 inches and 37 inches long respectively. The effects of global climate change are another element of concern. The extent and thickness of
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#17327906854551416-445: A single ancestor, or diphyletic , recent genetic evidence suggests all three descended from a caniform ancestor most closely related to modern bears. Recent multigene analysis indicates the odobenids and otariids diverged from the phocids about 20–26 million years ago, while the odobenids and the otariids separated 15–20 million years ago. Odobenidae was once a highly diverse and widespread family, including at least twenty species in
1534-527: A single walrus was sighted on the shores of the Baltic Sea - at Rügen Island, Germany , Mielno , Poland and Skälder Bay , Sweden . In July 2022, there was a report of a lost, starving walrus (nicknamed as Stena ) in the coastal waters of the towns of Hamina and Kotka in Kymenlaakso , Finland , that, despite rescue attempts, died of starvation when the rescuers tried to transport it to
1652-458: A substantial breeding population occurred on isolated Sable Island , 100 mi (160 km) southeast of Nova Scotia and 500 mi (800 km) due east of Portland, Maine , until the early Colonial period. Abundant walrus remains have also been recovered from the southern North Sea dating to the Eemian interglacial period, when that region would have been submerged as it is today, unlike
1770-516: A unique three-dimensional habitat for marine organisms and are a source for understanding many ecological processes. Over the last century, they have been the focus of extensive research, particularly in trophic ecology, and continue to provoke important ideas that are relevant beyond this unique ecosystem. For example, kelp forests can influence coastal oceanographic patterns and provide many ecosystem services . However, humans have contributed to kelp forest degradation . Of particular concern are
1888-711: A vital art form. According to Adolf Erik Nordenskiöld , European hunters and Arctic explorers found walrus meat not particularly tasty, and only ate it in case of necessity; however walrus tongue was a delicacy. Walrus hunts are regulated by resource managers in Russia , the United States, Canada, and Greenland , and by representatives of the respective hunting communities. An estimated four to seven thousand Pacific walruses are harvested in Alaska and in Russia, including
2006-436: A year before weaning, but the young can spend up to five years with the mothers. Walrus milk contains higher amounts of fats and protein compared to land animals but lower compared to phocid seals . This lower fat content in turn causes a slower growth rate among calves and a longer nursing investment for their mothers. Because ovulation is suppressed until the calf is weaned, females give birth at most every two years, leaving
2124-460: Is 3.6 cu km of ocean space available somewhere for marine habitats. Intertidal zones , those areas close to shore, are constantly being exposed and covered by the ocean's tides . A huge array of life lives within this zone. Shore habitats range from the upper intertidal zones to the area where land vegetation takes prominence. It can be underwater anywhere from daily to very infrequently. Many species here are scavengers, living off of sea life that
2242-470: Is a confined shallow aquifer. It has a basin ground surface area of 79,724 acres (32,263 ha) and an estimated groundwater storage capacity of 960,000 acre-feet. The depth to groundwater is about 100 feet (30 m). The groundwater in the San Diego Formation is brackish, and its quality is considered to be fair to poor. Due to its proximity to the ocean, the risk of seawater intrusion is
2360-424: Is a highly important link in the food chain, with hundreds of species feeding on seagrasses worldwide, including green turtles , dugongs , manatees , fish , geese , swans , sea urchins and crabs . Walrus O. rosmarus rosmarus O. rosmarus divergens O. rosmarus laptevi (debated) The walrus ( Odobenus rosmarus ) is a large pinniped marine mammal with discontinuous distribution about
2478-481: Is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea . Estuaries form a transition zone between river environments and ocean environments and are subject to both marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of fresh water and sediment. The inflow of both seawater and freshwater provide high levels of nutrients in both
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#17327906854552596-508: Is common to all marine habitats. Beyond that many other things determine whether a marine area makes a good habitat and the type of habitat it makes. For example: There are five major oceans, of which the Pacific Ocean is nearly as large as the rest put together. Coastlines fringe the land for nearly 380,000 kilometres. Altogether, the ocean occupies 71 percent of the world surface, averaging nearly four kilometres in depth. By volume,
2714-555: Is estimated to have been at least 2,300 kg (5,000 lb). The Atlantic subspecies weighs about 10–20% less than the Pacific subspecies. Male Atlantic walrus weigh an average of 900 kg (2,000 lb). The Atlantic walrus also tends to have relatively shorter tusks and somewhat more of a flattened snout . Females weigh about two-thirds as much as males, with the Atlantic females averaging 560 kg (1,230 lb), sometimes weighing as little as 400 kg (880 lb), and
2832-411: Is highly variable, they generally have relatively few teeth other than the tusks. The maximal number of teeth is 38 with dentition formula: 3.1.4.2 3.1.3.2 , but over half of the teeth are rudimentary and occur with less than 50% frequency, such that a typical dentition includes only 18 teeth 1.1.3.0 0.1.3.0 Surrounding the tusks is a broad mat of stiff bristles ("mystacial vibrissae "), giving
2950-408: Is influenced by the size and shape of the coastline. Tides do not typically cause erosion by themselves; however, tidal bores can erode as the waves surge up river estuaries from the ocean. Waves erode coastline as they break on shore releasing their energy; the larger the wave the more energy it releases and the more sediment it moves. Sediment deposited by waves comes from eroded cliff faces and
3068-414: Is little evidence to prove this. Due to its great size and tusks, the walrus has only two natural predators: the orca and the polar bear . The walrus does not, however, comprise a significant component of either of these predators' diets. Both the orca and the polar bear are also most likely to prey on walrus calves. The polar bear often hunts the walrus by rushing at beached aggregations and consuming
3186-408: Is more like that of true seals, relying less on flippers and more on sinuous whole body movements. Also like phocids, it lacks external ears. The extraocular muscles of the walrus are well-developed. This and its lack of orbital roof allow it to protrude its eyes and see in both a frontal and dorsal direction. However, vision in this species appears to be more suited for short-range. While this
3304-406: Is moved along the coastline by the waves. Sediment deposited by rivers is the dominant influence on the amount of sediment located on a coastline. The sedimentologist Francis Shepard classified coasts as primary or secondary . Continental coastlines usually have a continental shelf , a shelf of relatively shallow water, less than 200 metres deep, which extends 68 km on average beyond
3422-428: Is nearby, there are large discharges of nutrient rich land runoff into coastal waters. Further, periodic upwellings from the deep ocean can provide cool and nutrient rich currents along the edge of the continental shelf. As a result, coastal marine life is the most abundant in the world. It is found in tidal pools , fjords and estuaries , near sandy shores and rocky coastlines, around coral reefs and on or above
3540-432: Is not easily shifted by waves and currents, and when it dries out, cakes into a solid. By contrast, sand is easily shifted by waves and currents, and when sand dries out it can be blown in the wind, accumulating into shifting sand dunes . Beyond the high tide mark, if the beach is low-lying, the wind can form rolling hills of sand dunes. Small dunes shift and reshape under the influence of the wind while larger dunes stabilise
3658-646: Is restricted according to a CITES Appendix 3 listing. In October 2017, the Center for Biological Diversity announced they would sue the U.S. Fish and Wildlife Service to force it to classify the Pacific Walrus as a threatened or endangered species. In 1952, walruses in Svalbard were nearly gone due to ivory hunting over a 300 years period, but the Norwegian government banned their commercial hunting and
San Diego Formation - Misplaced Pages Continue
3776-417: Is washed up on the shore. Many land animals also make much use of the shore and intertidal habitats. A subgroup of organisms in this habitat bores and grinds exposed rock through the process of bioerosion . Sandy shores, also called beaches , are coastal shorelines where sand accumulates. Waves and currents shift the sand, continually building and eroding the shoreline. Longshore currents flow parallel to
3894-688: The Chukchi Sea through the relatively narrow Bering Strait . The majority of the population of the Pacific walrus spends its summers north of the Bering Strait in the Chukchi Sea of the Arctic Ocean along the northern coast of eastern Siberia , around Wrangel Island , in the Beaufort Sea along the northern shore of Alaska south to Unimak Island , and in the waters between those locations. Smaller numbers of males summer in
4012-833: The Gulf of Anadyr on the southern coast of the Siberian Chukchi Peninsula , and in Bristol Bay off the southern coast of Alaska, west of the Alaska Peninsula . In the spring and fall, walruses congregate throughout the Bering Strait, reaching from the western coast of Alaska to the Gulf of Anadyr. They winter over in the Bering Sea along the eastern coast of Siberia south to the northern part of
4130-493: The Kamchatka Peninsula , and along the southern coast of Alaska. A 28,000-year-old fossil walrus was dredged up from the bottom of San Francisco Bay , indicating that Pacific walruses ranged that far south during the last Ice Age . Commercial harvesting reduced the population of the Pacific walrus to between 50,000 and 100,000 in the 1950s–1960s. Limits on commercial hunting allowed the population to increase to
4248-721: The Korkeasaari Zoo for treatment. Walruses prefer shallow shelf regions and forage primarily on the sea floor, often from sea ice platforms. They are not particularly deep divers compared to other pinnipeds; the deepest dives in a study of Atlantic walrus near Svalbard were only 31 ± 17 m (102 ± 56 ft). However, a more recent study recorded dives exceeding 500 metres (1,600 ft) in Smith Sound , between NW Greenland and Arctic Canada – in general, peak dive depth can be expected to depend on prey distribution and seabed depth. The walrus has
4366-739: The North Pole in the Arctic Ocean and subarctic seas of the Northern Hemisphere . It is the only extant species in the family Odobenidae and genus Odobenus . This species is subdivided into two subspecies : the Atlantic walrus ( O. r. rosmarus ), which lives in the Atlantic Ocean , and the Pacific walrus ( O. r. divergens ), which lives in the Pacific Ocean . Adult walrus are characterised by prominent tusks and whiskers , and considerable bulk: adult males in
4484-746: The Slavic languages , which in turn borrowed it from Finno-Ugric languages, and ultimately (according to Ante Aikio ) from an unknown Pre-Finno-Ugric substrate language of Northern Europe. Compare морж ( morž ) in Russian, mursu in Finnish , morša in Northern Saami , and morse in French. Olaus Magnus , who depicted the walrus in the Carta Marina in 1539, first referred to
4602-632: The Steller's sea cow . Marine habitats A marine habitat is a habitat that supports marine life . Marine life depends in some way on the saltwater that is in the sea (the term marine comes from the Latin mare , meaning sea or ocean). A habitat is an ecological or environmental area inhabited by one or more living species . The marine environment supports many kinds of these habitats. Marine habitats can be divided into coastal and open ocean habitats. Coastal habitats are found in
4720-463: The blastula in suspended development before it implants itself in the uterus. This strategy of delayed implantation , common among pinnipeds, presumably evolved to optimize both the mating season and the birthing season, determined by ecological conditions that promote newborn survival. Calves are born during the spring migration, from April to June. They weigh 45 to 75 kg (99 to 165 lb) at birth and are able to swim. The mothers nurse for over
4838-411: The marine ecosystem depends on dissolved nutrients washed down from the land. Ocean deoxygenation poses a threat to marine habitats, due to the growth of low oxygen zones. In marine systems, ocean currents have a key role determining which areas are effective as habitats, since ocean currents transport the basic nutrients needed to support marine life. Plankton are the life forms that inhabit
San Diego Formation - Misplaced Pages Continue
4956-431: The nature of the rocks they are made of – the harder the rocks the less likely they are to erode, so variations in rock hardness result in coastlines with different shapes. Tides often determine the range over which sediment is deposited or eroded. Areas with high tidal ranges allow waves to reach farther up the shore, and areas with lower tidal ranges produce deposition at a smaller elevation interval. The tidal range
5074-414: The primary producers in the ocean, at the start of the food chain . In turn, as the population of drifting phytoplankton grows, the water becomes a suitable habitat for zooplankton , which feed on the phytoplankton. While phytoplankton are tiny drifting plants, zooplankton are tiny drifting animals, such as the larvae of fish and marine invertebrates . If sufficient zooplankton establish themselves,
5192-492: The tides . Their productivity is largely dependent on the turbidity of the water. The main phytoplankton present are diatoms and dinoflagellates which are abundant in the sediment. Kelp forests are underwater areas with a high density of kelp . They form some of the most productive and dynamic ecosystems on Earth. Smaller areas of anchored kelp are called kelp beds . Kelp forests occur worldwide throughout temperate and polar coastal oceans. Kelp forests provide
5310-458: The 18th and 19th centuries, the walrus was heavily exploited by American and European sealers and whalers , leading to the near- extirpation of the Atlantic subspecies. As early as 1871 traditional hunters were expressing concern about the numbers of walrus being hunted by whaling fleets. Commercial walrus harvesting is now outlawed throughout its range, although Chukchi , Yupik and Inuit peoples are permitted to kill small numbers towards
5428-503: The Atlantic and Pacific subspecies indicate very restricted gene flow, but relatively recent separation, estimated at 500,000 and 785,000 years ago. These dates coincide with the hypothesis derived from fossils that the walrus evolved from a tropical or subtropical ancestor that became isolated in the Atlantic Ocean and gradually adapted to colder conditions in the Arctic. The modern walrus is mostly known from Arctic regions, but
5546-487: The Canadian Arctic, across Greenland , Svalbard , and the western part of Arctic Russia. There are eight hypothetical subpopulations of Atlantic walruses, based largely on their geographical distribution and movements: five west of Greenland and three east of Greenland. The Atlantic walrus once ranged south to Sable Island , off of Nova Scotia ; as late as the 18th century, they could be found in large numbers in
5664-793: The Greater Gulf of St. Lawrence region, sometimes in colonies of 7-8,000 individuals. This population was nearly eradicated by commercial harvest; their current numbers, though difficult to estimate, probably remain below 20,000. In April 2006, the Canadian Species at Risk Act listed the populations of northwestern Atlantic walrus in Québec , New Brunswick, Nova Scotia , Newfoundland and Labrador as having been eradicated in Canada. A genetically distinct population existed in Iceland that
5782-600: The Old Norse word hross ('horse'). For example, the Old Norse word hrosshvalr means 'horse-whale' and is thought to have been passed in an inverted form to both Dutch and the dialects of northern Germany as walros and Walross . An alternative theory is that it comes from the Dutch words wal 'shore' and reus 'giant'. The species name rosmarus is Scandinavian. The Norwegian manuscript Konungs skuggsjá , thought to date from around AD 1240, refers to
5900-406: The Pacific can weigh more than 2,000 kilograms (4,400 pounds) and, among pinnipeds , are exceeded in size only by the two species of elephant seals . Walrus live mostly in shallow waters above the continental shelves , spending significant amounts of their lives on the sea ice looking for benthic bivalve molluscs . Walruses are relatively long-lived, social animals, and are considered to be
6018-430: The Pacific female averaging 800 kg (1,800 lb). Length typically ranges from 2.2 to 3.6 m (7 ft 3 in to 11 ft 10 in). Newborn walruses are already quite large, averaging 33 to 85 kg (73 to 187 lb) in weight and 1 to 1.4 m (3 ft 3 in to 4 ft 7 in) in length across both sexes and subspecies. All told, the walrus is the third largest pinniped species, after
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#17327906854556136-531: The Pacific subspecies far exceeds normal dimensions. In 1909, a walrus hide weighing 500 kg (1,100 lb) was collected from an enormous bull in Franz Josef Land , while in August 1910, Jack Woodson shot a 4.9-metre-long (16 ft) walrus, harvesting its 450 kg (1,000 lb) hide. Since a walrus's hide usually accounts for about 20% of its body weight, the total body mass of these two giants
6254-495: The Pacific, but the importance of seals in the walrus diet is under debate. There have been isolated observations of walruses preying on seals up to the size of a 200 kg (440 lb) bearded seal . Rarely, incidents of walruses preying on seabirds, particularly the Brünnich's guillemot ( Uria lomvia ), have been documented. Walruses may occasionally prey on ice-entrapped narwhals and scavenge on whale carcasses but there
6372-451: The area that extends from as far as the tide comes in on the shoreline out to the edge of the continental shelf . Most marine life is found in coastal habitats, even though the shelf area occupies only seven percent of the total ocean area. Open ocean habitats are found in the deep ocean beyond the edge of the continental shelf. Alternatively, marine habitats can be divided into pelagic and demersal zones . Pelagic habitats are found near
6490-461: The beaches, making waves break obliquely on the sand. These currents transport large amounts of sand along coasts, forming spits , barrier islands and tombolos . Longshore currents also commonly create offshore bars , which give beaches some stability by reducing erosion. Sandy shores are full of life, The grains of sand host diatoms , bacteria and other microscopic creatures. Some fish and turtles return to certain beaches and spawn eggs in
6608-685: The biological walrus's appetite for bivalve mollusks, oysters, primarily nearshore and intertidal inhabitants, these organisms in fact comprise an insignificant portion of its diet in captivity. The "walrus" in the cryptic song " I Am the Walrus " by the Beatles is a reference to the Lewis Carroll poem. Another appearance of the walrus in literature is in the story "The White Seal" in Rudyard Kipling 's The Jungle Book , where it
6726-419: The body of an individual organism is known as a thallus rather than as a plant (Kingdom: Plantae ). The morphological structure of a kelp thallus is defined by three basic structural units: In addition, many kelp species have pneumatocysts , or gas-filled bladders, usually located at the base of fronds near the stipe. These structures provide the necessary buoyancy for kelp to maintain an upright position in
6844-493: The coast. Worldwide, continental shelves occupy a total area of about 24 million km (9 million sq mi), 8% of the ocean's total area and nearly 5% of the world's total area. Since the continental shelf is usually less than 200 metres deep, it follows that coastal habitats are generally photic , situated in the sunlit epipelagic zone . This means the conditions for photosynthetic processes so important for primary production , are available to coastal marine habitats. Because land
6962-514: The continental shelf. Coastal fish include small forage fish as well as the larger predator fish that feed on them. Forage fish thrive in inshore waters where high productivity results from upwelling and shoreline run off of nutrients. Some are partial residents that spawn in streams, estuaries and bays, but most complete their life cycle in the zone. There can also be a mutualism between species that occupy adjacent marine habitats. For example, fringing reefs just below low tide level have
7080-414: The current becomes a candidate habitat for the forage fish that feed on them. And then if sufficient forage fish move to the area, it becomes a candidate habitat for larger predatory fish and other marine animals that feed on the forage fish. In this dynamic way, the current itself can, over time, become a moving habitat for multiple types of marine life. Ocean currents can be generated by differences in
7198-501: The density of the water. How dense water is depends on how saline or warm it is. If water contains differences in salt content or temperature, then the different densities will initiate a current. Water that is saltier or cooler will be denser, and will sink in relation to the surrounding water. Conversely, warmer and less salty water will float to the surface. Atmospheric winds and pressure differences also produces surface currents, waves and seiches . Ocean currents are also generated by
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#17327906854557316-435: The effects of overfishing nearshore ecosystems, which can release herbivores from their normal population regulation and result in the over-grazing of kelp and other algae. This can rapidly result in transitions to barren landscapes where relatively few species persist. Frequently considered an ecosystem engineer , kelp provides a physical substrate and habitat for kelp forest communities. In algae (Kingdom: Protista ),
7434-623: The end of each summer. Traditional hunters used all parts of the walrus. The meat, often preserved, is an important winter nutrition source; the flippers are fermented and stored as a delicacy until spring; tusks and bone were historically used for tools, as well as material for handicrafts; the oil was rendered for warmth and light; the tough hide made rope and house and boat coverings; and the intestines and gut linings made waterproof parkas. While some of these uses have faded with access to alternative technologies, walrus meat remains an important part of local diets, and tusk carving and engraving remain
7552-411: The environment is beneficial to many types of coral reef animals, which for example may feed in the sea grass and use the reefs for protection or breeding. Coastal habitats are the most visible marine habitats, but they are not the only important marine habitats. Coastlines run for 380,000 kilometres, and the total volume of the ocean is 1,370 million cu km. This means that for each metre of coast, there
7670-420: The equator, where currents curve left. Seabed topography (ocean topography or marine topography) refers to the shape of the land ( topography ) when it interfaces with the ocean. These shapes are obvious along coastlines, but they occur also in significant ways underwater. The effectiveness of marine habitats is partially defined by these shapes, including the way they interact with and shape ocean currents , and
7788-467: The gravitational pull of the sun and moon ( tides ), and seismic activity ( tsunami ). The rotation of the Earth affects the direction ocean currents take, and explains which way the large circular ocean gyres rotate in the image above left. Suppose a current at the equator is heading north. The Earth rotates eastward, so the water possesses that rotational momentum. But the further the water moves north,
7906-409: The humans live by the coast, putting pressure on coastal habitats. Mudflats are coastal wetlands that form when mud is deposited by tides or rivers. They are found in sheltered areas such as bays , bayous , lagoons , and estuaries . Mudflats may be viewed geologically as exposed layers of bay mud , resulting from deposition of estuarine silts , clays and marine animal detritus . Most of
8024-401: The increase of stampeding deaths crowding the shorelines of the Chukchi Sea between eastern Russia and western Alaska. Analysis of trends in ice cover published in 2012 indicate that Pacific walrus populations are likely to continue to decline for the foreseeable future, and shift further north, but that careful conservation management might be able to limit these effects. Currently, two of
8142-437: The individuals crushed or wounded in the sudden exodus, typically younger or infirm animals. The bears also isolate walruses when they overwinter and are unable to escape a charging bear due to inaccessible diving holes in the ice. However, even an injured walrus is a formidable opponent for a polar bear, and direct attacks are rare. Armed with its ivory tusks, walruses have been known to fatally injure polar bears in battles if
8260-858: The intervening glacial lowstand when the shallow North Sea was dry land. Fossils known from San Francisco , Vancouver , and the Atlantic US coast as far south as North Carolina have been referred to glacial periods. An isolated population in the Laptev Sea was considered by some authorities, including many Russian biologists and the canonical Mammal Species of the World , to be a third subspecies, O. r. laptevi (Chapskii, 1940), but has since been determined to be of Pacific walrus origin. While some outsized Pacific males can weigh as much as 2,000 kg (4,400 lb), most weigh between 800 and 1,700 kg (1,800 and 3,700 lb). An occasional male of
8378-446: The large black-headed loons; the latter was perhaps a small relative of the large grey-headed loons. Balaenoptera B. davidsonii An extinct rorqual belonging to Balaenoptera . "Balaenoptera" "B." portisi Formerly assigned to Balaenoptera , probably a member of Cetotheriophanes . Herpetocetus H. morrowi A cetotheriid . Norrisanima N. miocaena A stem-balaenopteroid, previously considered to be
8496-404: The large numbers of organisms actually consumed by the walrus, its foraging has a large peripheral impact on benthic communities. It disturbs ( bioturbates ) the sea floor, releasing nutrients into the water column, encouraging mixing and movement of many organisms and increasing the patchiness of the benthos . Seal tissue has been observed in a fairly significant proportion of walrus stomachs in
8614-502: The largest of any land mammal, both in absolute size and relative to body size. Walruses live to about 20–30 years old in the wild. The males reach sexual maturity as early as seven years, but do not typically mate until fully developed at around 15 years of age. They rut from January through April, decreasing their food intake dramatically. The females begin ovulating as soon as four to six years old. The females are diestrous , coming into heat in late summer and around February, yet
8732-416: The largest tusks typically dominate social groups. Tusks are also used to form and maintain holes in the ice and aid the walrus in climbing out of water onto ice. Tusks were once thought to be used to dig out prey from the seabed, but analyses of abrasion patterns on the tusks indicate they are dragged through the sediment while the upper edge of the snout is used for digging. While the dentition of walruses
8850-486: The latter follows the other into the water, where the bear is at a disadvantage. Polar bear–walrus battles are often extremely protracted and exhausting, and bears have been known to break away from the attack after injuring a walrus. Orcas regularly attack walruses, although walruses are believed to have successfully defended themselves via counterattack against the larger cetacean. However, orcas have been observed successfully attacking walruses with few or no injuries. In
8968-975: The leaves are long and narrow and are very often green, and because the plants often grow in large meadows which look like grassland. Since seagrasses photosynthesize and are submerged, they must grow submerged in the photic zone , where there is enough sunlight. For this reason, most occur in shallow and sheltered coastal waters anchored in sand or mud bottoms. Seagrasses form extensive beds or meadows , which can be either monospecific (made up of one species) or multispecific (where more than one species co-exist). Seagrass beds make highly diverse and productive ecosystems . They are home to phyla such as juvenile and adult fish, epiphytic and free-living macroalgae and microalgae , mollusks , bristle worms , and nematodes . Few species were originally considered to feed directly on seagrass leaves (partly because of their low nutritional content), but scientific reviews and improved working methods have shown that seagrass herbivory
9086-467: The males are fertile only around February; the potential fertility of this second period is unknown. Breeding occurs from January to March, peaking in February. Males aggregate in the water around ice-bound groups of estrous females and engage in competitive vocal displays. The females join them and copulate in the water. Gestation lasts 15 to 16 months. The first three to four months are spent with
9204-550: The marine environment to the point where they create further habitat for other organisms. By volume the ocean provides most of the habitable space on the planet. In contrast to terrestrial habitats, marine habitats are shifting and ephemeral . Swimming organisms find areas by the edge of a continental shelf a good habitat, but only while upwellings bring nutrient rich water to the surface. Shellfish find habitat on sandy beaches, but storms, tides and currents mean their habitat continually reinvents itself. The presence of seawater
9322-425: The more stable sedimental environment. However, large numbers of bacteria are found within the sediment which have a very high oxygen demand. This reduces the levels of oxygen within the sediment often resulting in partially anoxic conditions, which can be further exacerbated by limited water flux. Phytoplankton are key primary producers in estuaries. They move with the water bodies and can be flushed in and out with
9440-465: The nearby ice floes) hunting for bivalves . In March 2021, a single walrus, nicknamed Wally the Walrus , was sighted at Valentia Island , Ireland , far south of its typical range, potentially due to having fallen asleep on an iceberg that then drifted south towards Ireland. Days later, a walrus, thought to be the same animal, was spotted on the Pembrokeshire coast, Wales . In June 2022,
9558-402: The ocean contains more than 99 percent of the Earth's liquid water. The science fiction writer Arthur C. Clarke has pointed out it would be more appropriate to refer to the planet Earth as the planet Sea or the planet Ocean. Marine habitats can be broadly divided into pelagic and demersal habitats. Pelagic habitats are the habitats of the open water column , away from the bottom of
9676-421: The ocean that are so small (less than 2 mm) that they cannot effectively propel themselves through the water, but must drift instead with the currents. If the current carries the right nutrients, and if it also flows at a suitably shallow depth where there is plenty of sunlight, then such a current itself can become a suitable habitat for photosynthesizing tiny algae called phytoplankton . These tiny plants are
9794-421: The ocean which partially shape them. The Earth's natural processes, including weather and sea level change , result in the erosion , accretion and resculpturing of coasts as well as the flooding and creation of continental shelves and drowned river valleys . The main agents responsible for deposition and erosion along coastlines are waves , tides and currents . The formation of coasts also depends on
9912-459: The ocean. Demersal habitats are the habitats that are near or on the bottom of the ocean. An organism living in a pelagic habitat is said to be a pelagic organism, as in pelagic fish . Similarly, an organism living in a demersal habitat is said to be a demersal organism, as in demersal fish . Pelagic habitats are intrinsically ephemeral, depending on what ocean currents are doing. The land-based ecosystem depends on topsoil and fresh water, while
10030-505: The open ocean, they include underwater and deep sea features such as ocean rises and seamounts . The submerged surface has mountainous features, including a globe-spanning mid-ocean ridge system, as well as undersea volcanoes , oceanic trenches , submarine canyons , oceanic plateaus and abyssal plains . One measure of the relative importance of different marine habitats is the rate at which they produce biomass . Marine coasts are dynamic environments which constantly change, like
10148-522: The pack ice has reached unusually low levels in several recent years. The walrus relies on this ice while giving birth and aggregating in the reproductive period. Thinner pack ice over the Bering Sea has reduced the amount of resting habitat near optimal feeding grounds. This more widely separates lactating females from their calves, increasing nutritional stress for the young and lower reproductive rates. Reduced coastal sea ice has also been implicated in
10266-414: The populations of Atlantic and Laptev walruses remain fragmented and at low levels compared with the time before human interference. The origin of the word walrus derives from a Germanic language , and it has been attributed largely to either Dutch or Old Norse . Its first part is thought to derive from a word such as Old Norse hvalr ('whale') and the second part has been hypothesized to come from
10384-566: The rocks. Competition can develop for the rocky spaces. For example, barnacles can compete successfully on open intertidal rock faces to the point where the rock surface is covered with them. Barnacles resist desiccation and grip well to exposed rock faces. However, in the crevices of the same rocks, the inhabitants are different. Here mussels can be the successful species, secured to the rock with their byssal threads . Rocky and sandy coasts are vulnerable because humans find them attractive and want to live near them. An increasing proportion of
10502-648: The salinity of ocean seawater (up to 90 ppt). There are many mangrove species, not all closely related. The term "mangrove" is used generally to cover all of these species, and it can be used narrowly to cover just mangrove trees of the genus Rhizophora . Mangroves form a distinct characteristic saline woodland or shrubland habitat, called a mangrove swamp or mangrove forest . Mangrove swamps are found in depositional coastal environments, where fine sediments (often with high organic content) collect in areas protected from high-energy wave action. Mangroves dominate three quarters of tropical coastlines. An estuary
10620-410: The sand with vegetation. Ocean processes grade loose sediments to particle sizes other than sand, such as gravel or cobbles . Waves breaking on a beach can leave a berm , which is a raised ridge of coarser pebbles or sand, at the high tide mark. Shingle beaches are made of particles larger than sand, such as cobbles, or small stones. These beaches make poor habitats. Little life survives because
10738-552: The sand. Birds habitat beaches, like gulls , loons , sandpipers , terns and pelicans . Aquatic mammals , such sea lions, recuperate on them. Clams , periwinkles , crabs , shrimp , starfish and sea urchins are found on most beaches. Sand is a sediment made from small grains or particles with diameters between about 60 μm and 2 mm. Mud (see mudflats below) is a sediment made from particles finer than sand. This small particle size means that mud particles tend to stick together, whereas sand particles do not. Mud
10856-493: The sea bottom, searching and identifying prey with its sensitive vibrissae and clearing the murky bottoms with jets of water and active flipper movements. The walrus sucks the meat out by sealing its powerful lips to the organism and withdrawing its piston-like tongue rapidly into its mouth, creating a vacuum. The walrus palate is uniquely vaulted, enabling effective suction. The diet of the Pacific walrus consist almost exclusively of benthic invertebrates (97 percent). Aside from
10974-645: The sea, who is in turn linked to the Inuit goddess Sedna . Both in Chukotka and Alaska , the aurora borealis is believed to be a special world inhabited by those who died by violence, the changing rays representing deceased souls playing ball with a walrus head. Most of the distinctive 12th-century Lewis Chessmen from northern Europe are carved from walrus ivory, though a few have been found to be made of whales' teeth. Because of its distinctive appearance, great bulk, and immediately recognizable whiskers and tusks,
11092-614: The sediment within a mudflat is within the intertidal zone , and thus the flat is submerged and exposed approximately twice daily. Mangrove swamps and salt marshes form important coastal habitats in tropical and temperate areas respectively. Mangroves are species of shrubs and medium size trees that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes 25° N and 25° S. The saline conditions tolerated by various species range from brackish water , through pure seawater (30 to 40 ppt ), to water concentrated by evaporation to over twice
11210-525: The slower the earth moves eastward. If the current could get to the North Pole, the earth would not be moving eastward at all. To conserve its rotational momentum, the further the current travels north the faster it must move eastward. So the effect is that the current curves to the right. This is the Coriolis effect . It is weakest at the equator and strongest at the poles. The effect is opposite south of
11328-584: The southwestern corner of San Diego County from San Ysidro to Pacific Beach . San Diego Formation deposits were formed in a large, open, crescent-shaped bay similar in size to Monterey Bay that existed on the coast in Pliocene times. The formation contains the San Diego Formation Basin, a large aquifer under Imperial Beach , Chula Vista , National City , and southern portions of the city of San Diego. The San Diego Formation Basin
11446-403: The stones are churned and pounded together by waves and currents. The relative solidity of rocky shores seems to give them a permanence compared to the shifting nature of sandy shores. This apparent stability is not real over even quite short geological time scales, but it is real enough over the short life of an organism. In contrast to sandy shores, plants and animals can anchor themselves to
11564-468: The subfamilies Imagotariinae, Dusignathinae and Odobeninae. The key distinguishing feature was the development of a squirt/suction feeding mechanism; tusks are a later feature specific to Odobeninae, of which the modern walrus is the last remaining ( relict ) species. Two subspecies of walrus are widely recognized: the Atlantic walrus, O. r. rosmarus (Linnaeus, 1758) and the Pacific walrus, O. r. divergens (Illiger, 1815). Fixed genetic differences between
11682-466: The sun and the moon from an evil spirit by seducing his daughter, the angry father throws the daughter from a high cliff and, as she drops into the water, she turns into a walrus . According to various legends, the tusks are formed either by the trails of mucus from the weeping girl or her long braids. This myth is possibly related to the Chukchi myth of the old walrus-headed woman who rules the bottom of
11800-620: The surface or in the open water column , away from the bottom of the ocean. Demersal habitats are near or on the bottom of the ocean. An organism living in a pelagic habitat is said to be a pelagic organism, as in pelagic fish . Similarly, an organism living in a demersal habitat is said to be a demersal organism, as in demersal fish . Pelagic habitats are intrinsically shifting and ephemeral, depending on what ocean currents are doing. Marine habitats can be modified by their inhabitants. Some marine organisms, like corals , kelp , mangroves and seagrasses , are ecosystem engineers which reshape
11918-720: The three walrus subspecies are listed as "least-concern" by the IUCN , while the third is "data deficient". The Pacific walrus is not listed as "depleted" according to the Marine Mammal Protection Act nor as "threatened" or "endangered" under the Endangered Species Act . The Russian Atlantic and Laptev Sea populations are classified as Category 2 (decreasing) and Category 3 (rare) in the Russian Red Book . Global trade in walrus ivory
12036-428: The two elephant seals . Walruses maintain such a high body weight because of the blubber stored underneath their skin. This blubber keeps them warm and the fat provides energy to the walrus. The walrus's body shape shares features with both sea lions ( eared seals : Otariidae) and seals ( true seals : Phocidae). As with otariids, it can turn its rear flippers forward and move on all fours; however, its swimming technique
12154-429: The vibrissae, the walrus is sparsely covered with fur and appears bald. Its skin is highly wrinkled and thick, up to 10 cm (4 in) around the neck and shoulders of males. The blubber layer beneath is up to 15 cm (6 in) thick. Young walruses are deep brown and grow paler and more cinnamon-colored as they age. Old males, in particular, become nearly pink. Because skin blood vessels constrict in cold water,
12272-494: The walrus a characteristic whiskered appearance. There can be 400 to 700 vibrissae in 13 to 15 rows reaching 30 cm (12 in) in length, though in the wild they are often worn to much shorter lengths due to constant use in foraging. The vibrissae are attached to muscles and are supplied with blood and nerves, making them highly sensitive organs capable of differentiating shapes 3 mm ( 1 ⁄ 8 in) thick and 2 mm ( 3 ⁄ 32 in) wide. Aside from
12390-688: The walrus also appears in the popular cultures of peoples with little direct experience with the animal, particularly in English children's literature. Perhaps its best-known appearance is in Lewis Carroll 's whimsical poem " The Walrus and the Carpenter " that appears in his 1871 book Through the Looking-Glass . In the poem, the eponymous antiheroes use trickery to consume a great number of oysters . Although Carroll accurately portrays
12508-535: The walrus as rosmhvalr in Iceland and rostungr in Greenland (walruses were by now extinct in Iceland and Norway, while the word evolved in Greenland). Several place names in Iceland, Greenland and Norway may originate from walrus sites: Hvalfjord, Hvallatrar and Hvalsnes to name some, all being typical walrus breeding grounds. The archaic English word for walrus— morse —is widely thought to have come from
12626-542: The walrus as the ros marus , probably a Latinization of morž , and this was adopted by Linnaeus in his binomial nomenclature . The coincidental similarity between morse and the Latin word morsus ('a bite') supposedly contributed to the walrus's reputation as a "terrible monster". The compound Odobenus comes from odous ( Greek for 'teeth') and baino (Greek for 'walk'), based on observations of walruses using their tusks to pull themselves out of
12744-420: The walrus can appear almost white when swimming. As a secondary sexual characteristic , males also acquire significant nodules, called "bosses", particularly around the neck and shoulders. The walrus has an air sac under its throat which acts like a flotation bubble and allows it to bob vertically in the water and sleep. The males possess a large baculum (penis bone), up to 63 cm (25 in) in length,
12862-414: The walrus with the lowest reproductive rate of any pinniped. The rest of the year (late summer and fall), walruses tend to form massive aggregations of tens of thousands of individuals on rocky beaches or outcrops. The migration between the ice and the beach can be long-distance and dramatic. In late spring and summer, for example, several hundred thousand Pacific walruses migrate from the Bering Sea into
12980-517: The walruses began to repopulate. By 2018, the population had increased to an estimated 5,503 walruses in the Svalbard area. The walrus plays an important role in the religion and folklore of many Arctic peoples. Skin and bone are used in some ceremonies, and the animal appears frequently in legends. For example, in a Chukchi version of the widespread myth of the Raven , in which Raven recovers
13098-410: The water column and sediment, making estuaries among the most productive natural habitats in the world. Most estuaries were formed by the flooding of river-eroded or glacially scoured valleys when sea level began to rise about 10,000-12,000 years ago. They are amongst the most heavily populated areas throughout the world, with about 60% of the world's population living along estuaries and the coast. As
13216-517: The water column. The environmental factors necessary for kelp to survive include hard substrate (usually rock), high nutrients (e.g., nitrogen, phosphorus), and light (minimum annual irradiance dose > 50 E m ). Especially productive kelp forests tend to be associated with areas of significant oceanographic upwelling , a process that delivers cool nutrient-rich water from depth to the ocean's mixed surface layer . Water flow and turbulence facilitate nutrient assimilation across kelp fronds throughout
13334-694: The water column. Water clarity affects the depth to which sufficient light can be transmitted. In ideal conditions, giant kelp ( Macrocystis spp. ) can grow as much as 30-60 centimetres vertically per day. Some species such as Nereocystis are annual while others like Eisenia are perennial , living for more than 20 years. In perennial kelp forests, maximum growth rates occur during upwelling months (typically spring and summer) and die-backs correspond to reduced nutrient availability, shorter photoperiods and increased storm frequency. Seagrasses are flowering plants from one of four plant families which grow in marine environments. They are called seagrasses because
13452-589: The water. The term divergens in Latin means 'turning apart', referring to their tusks. The Inuttitut term for the creature is aivik , similar to the Inuktitut word: aiviq ᐊᐃᕕᖅ. The walrus is a mammal in the order Carnivora . It is the sole surviving member of the family Odobenidae, one of three lineages in the suborder Pinnipedia along with true seals ( Phocidae ) and eared seals ( Otariidae ). While there has been some debate as to whether all three lineages are monophyletic , i.e. descended from
13570-426: The way sunlight diminishes when these landforms occupy increasing depths. Tidal networks depend on the balance between sedimentary processes and hydrodynamics however, anthropogenic influences can impact the natural system more than any physical driver. Marine topographies include coastal and oceanic landforms ranging from coastal estuaries and shorelines to continental shelves and coral reefs . Further out in
13688-469: Was completed in 1999 and holds a production capacity of 4 million gallons of drinking water per day. The Claude "Bud" Lewis Carlsbad Desalination Plant in Carlsbad, California , was completed in 2015 and produces 50 million gallons of water per day. In this way, these plants contribute to reducing vulnerability and secure water supply, especially during drought periods. The use of groundwater contributes to
13806-406: Was not true of all extinct walruses, the most prominent feature of the living species is its long tusks. These are elongated canines , which are present in both male and female walruses and can reach a length of 1 m (3 ft 3 in) and weigh up to 5.4 kg (12 lb). Tusks are slightly longer and thicker among males, which use them for fighting, dominance and display; the strongest males with
13924-519: Was wiped out after Norse settlement around 1213–1330 AD. An isolated population is restricted, year-round, to the central and western regions of the Laptev Sea , from the eastern Kara Sea to the westernmost regions of the East Siberian Sea . The current population of these Laptev walruses has been estimated at between 5-10,000. Even though walruses can dive to depths beyond 500 meters, they spend most of their time in shallow waters (and
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