Seagrasses
Seagrasses are important in coastal marine areas. They are the main diet
of dugong and green turtles and provide a habitat for many, much smaller
marine animals, some of which, like prawns and fish, are commercially
important. They also stabilise sediment, helping to keep water clear.
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Dugong feeding trail in seagrass bed.
Photo: DPI |
Seagrasses are the only flowering plants (angiosperms) in the sea. Australia
has the highest number of seagrass species of any continent. Of some 60
seagrass species found worldwide, 30 species are found in Australia and
15 species are found in Queensland.
While there are over 500 species of algae, there are only 15 species
of seagrasses on the Great Barrier Reef. Seagrasses differ from algae
because they have seeds and fruits, rather than spores. Seagrasses also
have separate roots, leaves and underground stems called rhizomes which
form extensive networks below the surface. Algae rarely have roots below
the surface.
The distribution and abundance of tropical seagrass meadows can vary
with seasons. Queensland seagrasses are most abundant in November after
many months of clear skies, increasing day length and increasing temperature.
Many seagrass species flower and fruit from September to December in
Queensland coastal waters. The pollen from most species is carried from
the male flower to the separate female flowers. Flowering, however, is
not common for some tropical species and seagrasses can spread through
vegetative propagation by the growth and branching of rhizomes.
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Seagrass meadows can be very extensive.
Photo: DPI |
Some seagrass meadows are so extensive they can be seen from a space
shuttle orbiting earth. Recent studies by the Queensland Department of Primary Industries and Fisheries have found that up to 40 000 km2 of the
Great Barrier Reef lagoon is likely to have some vegetated habitat.
Seagrasses grow from the intertidal zone to depths depending on water
clarity. In Queensland, seagrasses have been found growing down to 58m
in clear reef waters near Lizard Island.
SEAGRASSES ARE PROTECTED. DON'T COLLECT THEM.
For more information on seagrasses:
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