Plant Communities

Plant diversity on Marion Island is low because of the island's isolation and harsh weather conditions. There are 22 indigenous flowering plants and ferns, and 165 species of lichens, mosses and liverworts. Nine of these species are endemic to the islands, and a further 34 are not found outside the South Indian Ocean province. Eighteen alien species have been introduced, of which12 have become established and can be found throughout the island. One of the indigenous flowering species, the Kerguelen Cabbage (Pringlea antiscorbutica), is of particular interest from a historical point of view. It contains high levels of vitamin C, and was regularly eaten by sailors and sealers to prevent scurvy. It currently holds high conservation status on the islands and although still commonly seen, an introduced moth (Plutella xylostella) and a fungus are threatening it. The various plant species on Marion Island tend to have particular associations because of common requirements for nutrients, water, slope, aspect and temperature. Thus they can be grouped into communities that are easily recognized.





Swamp communities:

Juncus scheuchzerioides - Blepharidophyllum densifolium bog and Agrostis magellanica mire. Forms on wet peat and possibly the most common vegetation complex at low altitudes.

Salt-spray communities:

Crassula moschata halopathic herbfield and Cotula plumosa herbfield. Restricted to shore-zone areas strongly affected by wind-blown sea spray.

Tussock grasslands:

Calltriche antarctica - Poa cookii . Nitrogen-loving plants which occur mainly around seal and penguin colonies, but also in well drained slopes where burrowing petrels nest.

Drainage lines:

Aceana magellanica - Brachythecium complex. Along riverbanks, in springs, flushes, water tracks and drainage lines where there is pronounced lateral subsurface water movement.

Fjaeldmark communities:

Andreaea - Racomitrium crispulum complex and Azorella selago .Forms on rocky areas strongly exposed to wind where it is scattered between loose slate-like rocks and boulders. Generally occurs above 100m asl.

Fernslope communities:

Blechnum penna-marina and Poa cookii - Aceana magellanica mixed herbfield. Forms on well-drained lowland slopes, high coastal cliffs and generally slopes inland of salt-spray zone.

Fresh water communities:

Ranunculus moseleyi and Limosella australis found in standing waters and form small mats on the floors of lakes and lakelets while Potamogetonspp. form a semi-floating mat on the surface of the water.

Marine communities:

Macrocystis pyrifera (Giant kelp beds) found 500 - 1000m offshore, in protected coves and in water 10 - 20 m deep. Lithothamnion sp. (Encrusting algae) is found in the intertidal zone, Durvillaea antarctica (Bull kelp) at shoreline cliffs and Porphyra sp. on spray zone boulders.