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 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 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) 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) 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) 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 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 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 spindle- shaped bodies – many are capable of long, deep repetitive dives (to 4500 ft depths and 2 hours).

Marine Mammals Northern fur seal Bearded 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 Overfishing Climate change