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Seaweek 2010: Oceans of Life - ours to explore; ours to restore

About our oceans

Who owns the oceans?

Under international law a nation owns its territorial (coastal) waters, which extend 12 nautical miles (22.2 km) beyond its coast. All ships may move freely outside that area. Each nation also has exclusive rights to all marine life in waters extending 200 nautical miles (322 km) beyond its shores. This is called exclusive economic zones (EEZ). The use and exploitation of the ocean is governed by the Law of the Sea Treaty (1982).

Australia has one of the largest Exclusive Economic Zones in the world. The total area being larger than the nation’s land area. Parts of the EEZ extend from Heard and McDonald Islands in the southwest to Norfolk Island in the east and from the Arafura Sea in the north to the Australian Antarctic Territory in the south.

Within our EEZ, Australia has sovereign rights to explore and exploit, conserve and manage the living (e.g. fisheries and genetic material) and non-living (e.g. oil, gas, minerals) natural resources. It also has jurisdiction over offshore installations, marine scientific research and the protection and preservation of the marine environment.

More information: Safeguarding Australia’s borders, Mike Pasfield

Australia's EEZ is shown
What is an ocean?
What are the Earth's oceans?
Who owns the oceans?
What's under the ocean?
Ocean Zones
Why are the oceans important?
What are the threats to our oceans?

What's under the ocean?

Beaches are one type of "barrier" separating land from sea, others include mudflats and mangroves.

The continental shelf is the extended coastline of a continent, it was part of the continent during the Ice Ages when sea levels were lower. The sea floor below the continental shelf is the continental slope which can slope at angles between 1o and 3o.

Abyssal plains are flat or very gently sloping areas of the deep ocean basin floor. A mid-ocean ridge is an underwater mountain range, usually having a valley known as a rift running along its spine, They form due to volcanic action below the ocean.

  Cross section of an ocean

A seamount is a mountain rising from the ocean seafloor that does not reach the water's surface. Most oceanic islands are volcanic in origin.

An oceanic trench is a long and narrow depression of the sea floor. They are the deepest parts of the ocean floor, the deepest being the Mariana Trench, at a depth of just under 11 km below sea level. Compare this to Mt. Everest which is almost 9 km above sea level.

More information: From Wikipedia, the free encyclopedia -begin with the Continental shelf.


Ocean Zones

Euphotic zone
From the surface to around 200 m

The euphotic zone is the depth of the water in an ocean, that receives enough sunlight for photosynthesis to occur. The depth of the photic zone can vary greatly depending on the turbidity of the water and the strenght and direction of sunlight.

The euphotic zone is where nearly all the primary production in the sea takes place. Photosynthesis occurs in this zone providing producer organims which can support large food webs.About 90% of all marine life lives in this region.

Disphotic zone
From 200 m to around 1,000 m

The mid layer of an ocean. It receives only very weak, filtered sunlight during the day. There is not enough light for photosynthesis to take place, so no plants live in this zone. There is not much food available in this zone.

Aphotic zone
From 1,000 m to around 4,000 m

The aphotic zone is the region of an ocean where less than 1% of sunlight penetrates. Most animals survive in this zone by consuming the snow of detritus falling from above or by preying on others.

This hawksbill turtle lives in the euphotic zone.

Giant isopods are common in the deep waters of the
Atlantic Ocean. They are sea floor scavengers
feeding on dead fish, whales, and squid.


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Marine and Atmospheric Research


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