Download The Marine Ecosystem

The Marine Ecosystem
Ocean Overview
Oceans cover three quarters of the
Earth's surface, and they are as diverse
as they are large.
 The ocean is a complicated ecosystem,
with very complex food chains and
animals that have adapted to a variety
of conditions.
 The ocean is home to the smallest
plankton and the largest creature on
earth, the blue whale.

Ocean Zonation

Because sunlight powers life on
Earth, one way the ocean is
subdivided is based on the amount
of light present. The light zones
are:
– The Euphotic (Sunlit) zone
– The Disphotic (Twilight) zone
– The Aphotic (Midnight) zone
The Sunlit Zone
The ‘top layer’ of the
ocean
 Goes down to about
600ft
 Is the only zone where
photosynthesis can
occur
 More than 90% of all
marine life is in this
zone

The Twilight Zone

600-3000 feet below
surface
 Light decreases and
pressure increases
 No plants in this zone
(not enough light)
 Animals have adapted
to dark waters
– Bioluminescence
The Midnight Zone
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90% of ocean water is
in this zone
NO LIGHT
Very high pressure
Temperatures near
freezing
Small amount of life
in this zone thrives
near thermal vents in
the ocean floor
Life of the Sunlit Zone
(Euphotic)

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Many types of aquatic plants and
algae
Marine mammals, such as seals,
whales and dolphins
A variety of fish
Lots of invertebrates
Plankton, which make up the
basis of the marine food chain
Most things you think of living in
the ocean are in this zone
Life of the Twilight Zone
(Disphotic)
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Lantern fish
Viperfish
Hatchet fish
Mid-water jellyfish
Oarfish(some can grow as
long as a school bus!)
Some squid and fish can
use their own bodies to
make light
– This is called
bioluminescence
Life of the Midnight Zone
(Aphotic)
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Angler fish
Sea cucumber
Gulper Eel
Oppusum shrinp
Vampire sqid
Everything in this zone is
nourished by bacteria that
live by nutrient rich
thermal vents in the ocean
floor
Other important terms

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Pelagic: The water part
of the ocean
Neritic: water from high
tide to 600 ft
Oceanic: water deeper
than 600 ft
Benthic:ocean bottom
Intertidal:area that is
exposed to air at low tide
Subtidal:area of shore
covered by water at high
or low tide
Alaska’s Marine Life

Alaska is surrounded by a lot
of water, and the coast line of
Alaska is longer than that of
the rest of the United States!
 There are many types of
animals that live in Alaska’s
waters or on the coastlines,
but the three main classes we
will talk about are:
– Birds, mammals and fish 
Coastline Birds

Alaska is widely recognized as a global
center for shorebirds
 Ninety percent of the migratory species in
the Western Hemisphere have breeding
populations in Alaska
 Examples are: sandpipers, terns, plovers and
puffins.
Marine Mammals

Cetaceans: Whale, dolphins and porpoises
– completely aquatic mammals
– body is streamlined
– breathe through nostrils (blowhole)
on top of the head
– grouped into two suborders
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Baleen whales
Toothed whales
Marine Mammals

Baleen Whales
– Right whales, rorquals,
gray whales

Toothed whales
– Sperm whales, beaked whales,
dolphins, beluga whales and porpoises
Marine Mammals

Pinnipeds: Seals, Sea Lions and Walruses
– Pinniped means ‘flipper foot’
– carnivores that have adapted to an amphibious marine
niche
– come ashore or onto ice at some time of the year to
mate, give birth, nurse their young
– four webbed flippers used to propel their spindleshaped bodies
– many are capable of long, deep repetitive dives (to
4500 ft depths and 2 hours).
Marine Mammals
Bearded seal
Northern fur seal
Crabeater Seal
Stellar Sea Lions
Walrus
Marine Mammals

Fissipeds: Sea otters and polar bears
– Fissiped means ‘split foot’
– more closely related to terrestrial carnivores
– lack many of the physiologic adaptations to
marine life seen in pinnipeds and cetaceans
– Both species are considered marine mammals
under U.S. laws because of the roles they play
in the marine environment.
Marine Mammals

Polar bears (bear family Ursidae)
– spend most of their lives associated with marine
ice and waters
– competent swimmers, but they are the marine
mammal least adapted to aquatic existence
– rest, mate, give birth, and nurse their young on
the ice
Marine Mammals

Sea otters (weasel family, Mustelidae)
– live a primarily marine life
– they rest, mate, give birth, and nurse their young in the
water
– hind limbs are webbed for swimming, but their front
paws are padded with separate, clawed digits
– lack blubber, but are insulated by air trapped in their
thick fur, which is densest among all mammals.
Ocean Fish/Crustaceans

Many types of fish play an important role in
Alaska’s marine environments.
 Many are economically important,
including halibut, salmon, pollock, and
crustaceans such as crab and shrimp.
Mariculture

Mariculture: farming or ranching of marine
organisms
– Most commonly farmed in AK is the Pacific
oyster
– Others are littleneck clams, mussels, scallops,
sea cucumbers, and seaweed
– Most commonly ‘ranched’
are salmon--hatcheries
Threats to the Marine
Ecosystem

Pollution
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Overfishing
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Climate change