The Southern Ocean - Sunken Valley, South West Tasmania
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The Southern Ocean
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Introduction
The Southern Ocean, which circles the globe without being blocked by land, is home to the Antarctic Circumpolar Current (ACC), the longest of the world's ocean currents. Also known as the "channel", it connects the Indian, Atlantic and Pacific Ocean basins and exerts a powerful influence over the Earth's climate. The ACC carries 150 times more water around Antarctica than the flow of all the world's rivers combined.
The sunken valley, South West Tasmania
Overview
In a remote south-western corner of Tasmania is the pristine 'sunken valley'. This unusual estuarine system within the areas of Port Davey and Bathurst Harbour is home to species of marine wildlife that usually exist in much deeper water.
A surface layer of fresh water is stained dark brown by tannins that leach in from the peat soils of surrounding land. This layer extends 3-6m deep, blocking the sunlight and causing the clear salt water below to be very dark. This dark, clear salt water replicates conditions usually experienced at 400m depth and is the perfect habitat for species such as sea pens and sea whips.
| Importance: | Deep sea marine species can be found at relatively shallow depths. |
| Dive category: | Diving through the dark tannin layer may cause disorientation and must only be attempted by experienced divers. Also due to the fragility of wildlife in this area, divers should have good buoyancy control and not come into contact with the sea bed or stir up sediment with careless fin kicks. |
| Access: | This is a fragile site within Tasmania's Southwest National Park and is protected by strict regulations. Some areas are so fragile that recreational diving is only allowed with a permit. |
Interesting for
- A marine reserve, unspoilt by humans
- The Parks and Wildlife Service of Tasmania website describes the highlights, including the wildlife, found in this marine reserve.
- Port Davey and Bathurst Marine Reserve
- A remote corner of Tasmania
- Wikipedia describes the history, flora and fauna of this remote national park.
- South West Wilderness
- Biology of the sea pen
- The Monterey Bay Aquarium website explains the biology of the sea pen.
- Sea pen
BBC related content
- Oceans presenter biography: Tooni Mahto
- Oceans presenter biography: Paul Rose
- Oceans image gallery: The Southern Ocean
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