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Tasmanian seagrass communities


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Rees, CG 1993 , 'Tasmanian seagrass communities', Coursework Master thesis, University of Tasmania.

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Available under University of Tasmania Standard License.

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Seagrasses are marine angiosperms that grow in sheltered coastal and estuarine
water bodies. They play a significant role in coastal marine ecology, and are
important breeding and feeding grounds for a number of fish species. However,
seagrasses are vulnerable to the impacts of some human activities through their
sensitivity to reduced light energy. This may be lowered by increased turbidity
and sedimentation, or the excessive growth of algal epiphytes in response to
raised nutrient levels.
Five seagrass species occur in Tasmania, Amphibolis antarctica (Labill.) Sonder et
Aschers., Halophila australis Doty & Stone, Heterozostera tasmanica (Marten ex
Aschers.), Posidonia australis Hook. f. and Zostera muelleri Irmisch & Aschers.,
their presence or absence defining five zones around the Tasmanian coast. Most
coastal areas were sampled., and seagrass beds located. When sampling these
beds, the species, depth, density, substratum and presence of algal epiphytes
were recorded. Using available aerial photography from three time periods
(circa 1950.� circa 1970 and the present)., seagrass beds in selected areas were
digitally mapped into a GIS database using ARC/INFO. The sample site attributes
were added to the database, and patterns of distribution and change analysed
and mapped.
The five seagrass species have distinct zonation patterns and distributions in
relation to region.� coastal formation, substratum and depth. An area of
approximately 220 km2 was mapped, leading to speculation that from 400 to
500 km2 of sea grass rna y occur in Tasmania. However, the results of the analysis
and mapping also indicate significant decline. Total loss has occurred in some
areas. Decline is most pronounced in those parts of the State close to centres of
human population and activity.
There is a strong relationship between the seagrass decline in coastal areas and
the presence and abundant of algal epiphytes. Ambient nutrient levels in some
coastal water bodies are likely to be a major cause of seagrass decline. In this
context, this thesis proposes some mechanisms for the management and
protection of Tasmania's seagrass communities.� and nominates representative
coastal areas for possible reserve status.

Item Type: Thesis - Coursework Master
Authors/Creators:Rees, CG
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