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Into The Seas
And Oceans
Biological riches of the seas and ocean |
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The combination and variation of physical
factors (ice, rock, sand and mud substrate, temperature, salinity,
water movement, nutrients, light) determine the biology of the system. |
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The coasts. Estuaries and deltas with
salt marshes and mudflats, sandy and rocky shores, bays, inlets
and fjords, cliffs. These are the transition zones between land
and sea - a foot in both camps. The narrow shores and wider deltas
provide places to feed and breed. It is the birds that give the
outward and visible signs of the productivity of the seas. They
migrate North for the short summer, covering thousands of kilometers
from temperate and tropical regions, even as far as the Antarctic
in the case of the Arctic tern - an annual round trip of 32 thousand
kilometers. |
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On the mudflats and sandy shores,
vast numbers of waders pick and probe for small crustaceans, molluscs,
worms and small fish. Waders (dunlin, knot, sandpipers and stints)
breed almost exclusively in the Arctic with total populations of
individual species of up to 3.5 million birds, some of them also
using the tundra wetlands. Terns breed in colonies and dive
for small fish in coastal waters. Vast colonies, sometimes several
hundred thousands, of guillemots (murres), auks, gannets, cormorants
and puffins nest on high cliffs or burrows in the turf. They fish
for capelin, sandeels, Polar cod and other fish. They are harassed
by skuas and gulls. Their guano fertilises the vivid green patches
of vegetation. The cliffs, filled with their cacophony in summer
are silent in winter. |
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Continental shelves, seas and oceans.
The shallow coastal waters support considerable and diverse bottom
fauna of crustacea, molluscs, sponges, worms, anemones and starfish
with various small fish. They graze the algae or feed on detritus
or plankton and provide a food source for larger fish, birds and
mammals such as walrus and seals. The shallow waters are also the
spawning ground for capelin, polar cod and other fish in March and
April. Each school of capelin can contain many hundreds of tonnes
of fish which then move out to deeper waters and the sea ice edge
to feed on plankton - and to be preyed on by seabirds, larger fish
such as cod, seals and whales. Ice plays an important role in the
marine ecology. In winter the sea ice extends far South with maximum
extent in March. |
Maximum and minimum sea-ice extent. |
It retreats during summer, leaving
the Arctic Ocean permanently covered by three meters or more of
pack ice, with ridges both above and below surface (see
figure 14). Yet even in the pack ice, there is open water (polynyas)
even in winter, caused by wind and water movement and the upwelling
of warmer water. In summer about 10% of the pack ice is open water.
Nutrients transported from the rivers, from upwelling deeper waters
or deposited from the atmosphere, provide the chemical base for
the growth of algae. They grow on the surface, in and under the
ice, and in the open water. They are adapted to grow at low temperatures,
but also thrive where temperatures are enhanced by water from the
Global Conveyer Belt. They can also grow in the minimal light that
diffuses through the ice. These algae - the primary producers -
are the key to the productive food chains of the Arctic seas and
ocean. |
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The ice edge, especially in
shallower waters, is a very productive zone. A complex food web
is developed that extends from the algal grazers, through various
predators up to the polar bear and Arctic fox which move far out
onto the ice to feed. In the open water the floating algae or phytoplankton
are the food source for small and large crustacea (krill) which
are the food for the herring, capelin and the various species of
baleen whales - the filter feeders. |
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