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The Marine Ecosystem of the Sub-Antarctic, Prince Edward Islands.

作者:I.J. Ansorge, P.W. Froneman, J.V. Durgadoo,
出版單位:InTech
核准日期:2012-03-02
類型:Book Section PeerReviewed

英文摘要

[from the Introduction]
Straddled between the northern and southern boundaries of the Antarctic Circumpolar
Current (ACC), Sub-antarctic islands are typically oceanic; experiencing moist, cool and
windy climates. They are classified as regions, in which the terrestrial and marine
ecosystems are relatively simple and extremely sensitive to perturbations. One such
example are the Prince Edward Islands - the most southerly part of South Africa’s official
territory. The islands are located in the Indian sector of the Southern Ocean at
approximately 46°50’S and 37°50’E (Figure 1). The nearest landfall is the Crozet Island
Group 950 km to the east, while South Africa lies over 2 000 km northwest. The islands
consist of Marion and Prince Edward Island (Figure 1 - insert), two volcanic outcrops
approximately 250 000 years old, but still active. Marion Island covers an area of 270 km2;
whereas Prince Edward Island – 19 km to the north-east – is only about 45 km2 in extent.
The islands rise steeply from a region of complex bottom topography with a shallow
saddle, between 40 and 200 m deep, separating Prince Edward from Marion Island.
Intensive investigations carried out on the oceanic frontal systems south of Africa
(Lutjeharms & Valentine, 1984; Duncombe Rae, 1989 a,b; Belkin & Gordon, 1996) have
shown that the Prince Edward Islands lie directly in the path of the ACC, sandwiched
between the Sub-antarctic Front (SAF) and the Antarctic Polar Front (APF). As such, these
islands provide an ideal ecological laboratory for studying how shifts in atmospheric and
oceanic circulation patterns in the Southern Ocean will increase the ease in which these
islands, their ecosystems and their ocean surrounds can be invaded by alien species
(Smith, 2002).
The Prince Edward Islands, like many other oceanic islands within the Southern Ocean, are
seasonally characterised by vast populations of marine organisms and a diversity and
abundance of seabirds that use the islands as breeding grounds (Bergstrom & Chown, 1999;
Ryan & Bester, 2008). It is estimated that the islands support over 5 million breeding pairs of
top predators including flying seabirds, penguins and seals during the peak in breeding
season. The energy necessary to sustain these top predators is derived from the surrounding marine environment. Changes in the marine ecosystem in response to global climate change
are therefore, likely to dramatically influence the populations of top predators that
seasonally occur on the islands (Ryan & Bester, 2008).


committee_member - Cruzado, A.


 

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