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walruses

The walrus (Odobenus rosmarus) is a large flippered marine mammal with a discontinuous circumpolar distribution in the Arctic Ocean and sub-Arctic seas of the Northern Hemisphere. The walrus is the only living species in the Odobenidae family and Odobenus genus. It is subdivided into three subspecies: the Atlantic Walrus (O. rosmarus rosmarus) found in the Atlantic Ocean, the Pacific Walrus (O. rosmarus divergens) found in the Pacific Ocean, and O. rosmarus laptevi, found in the Laptev Sea.

The walrus is immediately recognized by its prominent tusks, whiskers and great bulk. Adult Pacific males can weigh up to 2,000 kilograms (4,400 lb) and, among pinnipeds, are exceeded in size only by the two species of elephant seals. It resides primarily in shallow oceanic shelf habitat, spending a significant proportion of its life on sea ice in pursuit of its preferred diet of benthic bivalve mollusks. It is a relatively long-lived, social animal and is considered a keystone species in Arctic marine ecosystems.

The walrus has played a prominent role in the cultures of many indigenous Arctic peoples, who have hunted the walrus for its meat, fat, skin, tusks and bone. In the 19th and early 20th centuries, the walrus was the object of heavy commercial exploitation for blubber and ivory and its numbers declined rapidly. Its global population has since rebounded, though the Atlantic and Laptev populations remain fragmented and at historically depressed levels.



 
 

Marine Ecology


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Inter Tidal Zone

The intertidal area (also called the littoral zone) is where the land and sea meet, between the high and low tide zones. This complex marine ecosystem is found along coastlines worldwide. It is rich in nutrients and oxygen and is home to a variety of organisms.

inter tidal zones

Examples:

  • sandy beaches
  • rocks
  • estuaries
  • mangrove swamps
  • coral reefs

Some of these regions are very productive. Many of their inhabitants have adaptations that enable them to survive periodic exposure to the air and wave action.

An Inhospitable, Changing Environment:

Much of this inhospitable environment is washed by the tides each day, so organisms that live here are adapted to huge daily changes in moisture, temperature, turbulence (from the water), and salinity.

Moisture:

The littoral zone is covered with salt water at high tides, and it is exposed to the air at low tides; the height of the tide exposes more or less land to this daily tide cycle. Organisms must be adapted to both very wet and very dry conditions.

Water Movement:

The turbulence of the water is another reason that this area can be very difficult one in which to survive - the rough waves can dislodge or carry away poorly-adapted organisms. Many intertidal animals burrow into the sand (like clams), live under rocks, or attach themselves to rocks (like barnacles and mussels).

Temperature:

The temperature ranges from the moderate temperature of the water to air temperatures that vary from below freezing to scorching.

Salinity:

Depressions on the shores sometimes form tide pools, areas that remain wet, although they are not long-lasting features. The salinity of tidepools varies from the salinity of the sea to much less salty, when rainwater or runoff dilutes it. Animals must adapt their systems to these variations. Some fish, like sculpin and blennies, live in tide pools.

Vertical Zones eg :Rocky Shores

The rocky intertidal habitat has a very rich diversity of organisms especially in temperate climates. Attachment is critical and competition for space is a prime factor. The organisms are well adapted for withstanding tremendous SURF-EXPOSURE. Also tolerance to DESICCATION (low tides during the summer days), temperature changes, and salinity changes( rainfall during low tide).

When the tide goes out, the phenomenon of ZONATION is manifested - horizontal bands or zones of organisms. This is true for both plants and animals. Each zone has a particular color or texture from the organisms inhabiting that particular zone. UNIVERSAL PATTERNS of zonation, occurring throughout the world, have been recognized, such that no matter where you might be observing the exposed intertidal, the middle littoral zone will often have a community of barnacles, mussels, and rockweeds

The intertidal area or littoral area is divided into vertical zones like bands. The names that are often used to describe these zones are the spray zone, high tide zone, middle tide zone, and low tide zone. Below these is the sub-tide zone (marine evironment or subtidal area) , which is always underwater.

Spray Zone: Also called the Upper Littoral, the Supralittoral Fringe, the Splash Zone, and the Barnacle Belt. This area is dry much of the time, but is sprayed with salt water during high tides. It is only flooded during storms and extremely high tides. Organisms in this sparse habitat include barnacles, isopods, lichens, lice, limpets, periwinkles, and whelks. Very little vegetation grows in this area.[More information and common species in this zone here]

splash zone

High Tide Zone: Also called the Upper Mid-littoral Zone (Upper Eulittoral) and the high intertidal zone. This area is flooded only during high tide. Organisms in this area include anemones, barnacles, brittle stars, chitons, crabs, green algae, isopods, limpets, mussels, sea stars, snails, whelks and some marine vegetation. [More info here]

high tide zone

Middle Tide Zone: Also called the Lower Mid-littoral Zone (Lower Eulittoral) . This turbulent area is covered and uncovered twice a day with salt water from the tides. Organisms in this area include anemones, barnacles, chitons, crabs, green algae, isopods, limpets, mussels, sea lettuce, sea palms, sea stars, snails, sponges, and whelks.[More info here]

low tide zone

Low Tide Zone: Also called the Lower Littoral Zone (Sublittoral Fringe). This area is usually under water - it is only exposed when the tide is unusually low. Organisms in this zone are not well adapted to long periods of dryness or to exteme temperatures. Some of the organisms in this area are abalone, anemones, brown seaweed, chitons, crabs, green algae, hydroids, isopods, limpets, mussels, nudibranchs, sculpin, sea cucumber, sea lettuce, sea palms, sea stars, sea urchins, shrimp, snails, sponges, surf grass, tube worms, and whelks.

 

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tidal zones

Predators:

Animals that live in the littoral zone have a wide variety of predators who eat them. When the tide is in, littoral organisms are preyed upon by sea animals (like fish). When the tide is out, they are preyed upon by land animals, like foxes and people. Birds (like gulls) and marine mammals (like walruses) also prey on intertidal organisms extensively.

 
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