Coasts and Oceans Theme Report
Australia State of the Environment Report 2001 (Theme Report)
Australian State of the Environment Committee, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06751 5
Habitats and species (continued)
Seamounts
Seamounts are remnants of extinct volcanoes found in Australia's deep marine environment. They are typically cone-shaped, 200 to 500 metres high and several kilometres across. They are between 650 and 1000 metres below the sea surface.
A number of fields of seamounts exist beneath Australian waters, and these tend to have distinctive flora and fauna. One such field of about 70 seamounts lies between 50 and 170 kilometres south of Tasmania, in water 1000 to 2000 metres deep (Figure 8). There are also seamounts and ridges in the Australian marine environment to the east and north-west of Australia.
Figure 8: Location of the Tasmanian Seamounts Marine Reserve.
Source: Environment Australia (2000)
CSIRO's oceanographic survey ship Franklin .
Source: Environment Australia
Seamounts are frequently places of high biodiversity and the Tasmanian seamounts are important as places of aggregation of spawning Orange Roughy. A CSIRO study of southern seamounts (Koslow and Gowlett-Holmes 1998) collected a number of rare and previously undescribed fish species. Further, between 25% and 50% of the invertebrate species collected are believed to be new to science and between 31% and 48% are known only from this region. The diversity of this invertebrate seamount fauna was emphasised by comparing it with world-wide seamount invertebrate fauna.
Stalked crinoid or sea lily.
Source: CSIRO Marine Research, Hobart
The fauna of the Tasmanian seamounts are remarkably different from those of seamounts in the northern Tasman Sea (on the Lord Howe Rise and Norfolk Ridge) within the EEZ of New Caledonia (de Forges et al. 2000). The biodiversity of other Australian seamounts is still poorly understood and there is little or no information on Antarctic seamounts.
Deep ocean coral reef.
Source: CSIRO Marine Research, Hobart
The major pressure on seamounts is commercial fishing. Trawling on the shallow seamounts south of Tasmania has damaged this unique habitat through scraping of the substrate and removing the reef aggregate and associated flora and fauna.
The Commonwealth declared the Tasmanian Seamounts Marine Reserve in May 1999, comprising an area of 370 km2, to protect a sample of the unique bottom-dwelling communities associated with the seamount region. This is the first marine reserve of its type in the world. Under the Tasmanian Seamounts Marine Reserve Management Plan it is proposed to prohibit any commercial activity, below a depth of 500 metres, while in the upper 500 metres there is a multiple use zone, where limited commercial fishing may occur.
Basket star.
Source: CSIRO Marine Research, Hobart