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Prepared by the Marine Species Section
Approvals and Wildlife Division, Environment Australia
in consultation with the Marine Turtle Recovery Team
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July 2003
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Download Recovery Plan for Marine Turtles in Australia - PDF (marine-turtles.pdf - 567 KB)
from pages #23 & #33
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Dangers to Turtles
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Boat Strike
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Marine turtle mortality due to boat strike has been identified as an issue in Queensland waters, principally in Moreton
Bay and Hervey Bay. The need to restrict boat speed in areas of important marine turtle habitat is identified (Table 12)
and opportunities for awareness raising and educative activities with boat users should be utilised.
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Seagrass Feeding Habitat
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Seagrass communities are essential habitats for several marine turtles but particularly green turtles. Tropical and subtropical
Australia is one of the richest areas in the world with respect to seagrasses. Despite the extensive area and
species diversity of seagrasses, there have been reports of declines in seagrasses in tropical and sub-tropical Australia.
Changes in seagrass occur at a range of spatial and temporal scales due to man-made and natural causes and the
complex interaction of the two. In 1985 cyclone Sandy caused a 183 km2 loss of seagrass in the Gulf of Carpentaria,
which was 20 per cent of the seagrasses of the Gulf. After 12 years, much of the area had recovered to pre-cyclone
levels but there is still a large area (20 km2) devoid of seagrass that previously supported seagrass communities
(Poiner et.al. 1993). In 1992-93 an estimated 900 km2 of seagrass in Hervey Bay in Queensland disappeared. The
cause of this loss is not known although it is thought that high turbidities, resulting from flooding of the Mary and
Burrum Rivers, and run off from cyclone Fran three weeks later, were responsible (Preen et.al. 1993). Similarly
1199 km2 of seagrass in the Torres Strait was lost probably due to high turbidities, resulting from flooding of the Mai
River (Long et.al. 1997).
Seagrass declines in Moreton Bay have been attributed to the deterioration of water quality from urbanisation,
industrialisation and increased land use resulting in increases in nutrient loading, sedimentation, influx of
contaminants and toxins or other detrimental effects on seagrass communities (Kirkman 1978, Hyland et.al. 1989,
Abal and Dennison 1996).
Outbreaks of Lyngbya majuscula, a cynobacterium commonly known as mermaid’s hair or fireweed, can have major
impacts on ecosystem health. In bloom conditions Lyngbya forms dense mats that cover the sea floor, smothering
underlying seagrass meadows.
Seagrass systems do not readily recover. The plants require appropriate water quality and special conditions in the
substrate that are not present in disturbed or most sandy substrates. Consequently, once an area has been denuded of
seagrass, it may not recover or may take a long time.
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