The Marine EcosystemThe Marine Ecosystem

Ocean OverviewOcean 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 ZonationOcean 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 ZoneThe 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 ZoneThe 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 ZoneThe Midnight Zone

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 Life of the Sunlit Zone (Euphotic)(Euphotic)

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 Life of the Twilight Zone (Disphotic)(Disphotic)

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 Life of the Midnight Zone (Aphotic)(Aphotic)

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 termsOther important terms

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 LifeAlaska’s Marine LifeAlaska 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 BirdsCoastline 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 MammalsMarine 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

Baleen whales Toothed whales

Marine MammalsMarine Mammals

Baleen Whales– Right whales, rorquals, gray whales

Toothed whales– Sperm whales, beaked whales, dolphins, beluga whales and porpoises

Marine MammalsMarine 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 spindle-

shaped bodies– many are capable of long, deep repetitive dives (to

4500 ft depths and 2 hours).

Marine MammalsMarine Mammals

Northern fur seal

Bearded seal

Crabeater Seal

Stellar Sea Lions

Walrus

Marine MammalsMarine 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 MammalsMarine 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 MammalsMarine 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/CrustaceansOcean 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.

MaricultureMariculture

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 Threats to the Marine EcosystemEcosystem

Pollution

Overfishing

Climate change