Much of the information contained in the package has been drawn from South Australia’s first comprehensive study of the conservation status of the fish, sharks and rays that inhabit the waters off SA: Baker, J.L. (2008 in prep.) Status of Marine Species at Risk in South Australia: Technical Report – Bony and Cartilaginous Fish.
The package was developed by the Conservation Council of South Australia Inc. (CCSA) with funding provided by WWF Australia. This work was supported by a Reference Group involving representatives from the Dept for Environment and Heritage, Primary Industries and Resources SA (PIRSA) Fisheries, the Adelaide and Mount Lofty Ranges NRM Board, the Threatened Species Network (WWF), and Janine Baker, author of the above report.
CCSA sincerely Thanks:
• the members of the Reference Group - in particular Janine Baker whose assistance has been invaluable; and
• WWF -Australia, especially the SA Threatened Species Co-ordinator, Vicki-Jo Russell for her support for the project.
The Unique South
South Australian marine life is part of a great southern temperate marine region stretching from near Pperth around Tasmania and up to Sydney. This extraordinary region – increasingly known as “the unique south” – has extremely high levels of biodiversity and endemism (i.e. species that are not found anywhere else in the world). This is mainly due to it being:
- 1. the longest south-facing stretch of coast in the world;
- 2. extremely stable and isolated for millions of years;
- 3. in the centre of an east-west convergence of currents, which have both contributed to the biodiversity of South Australia’s marine life and cut it off from spreading to the rest of the world; and
- 4. a region with unusually low nutrient levels for a temperate region unlike other temperate regions in the world, which are typically high in nutrients.
All of these factors contribute to the high levels of biodiversity and endemicity. For example, South Australia has over 1200 species of macroalgae, ~ 200 species of sea squirts, and ~ 500 species of bryozoans – both of these latter groups have more species in South Australia than any other region in the world.
Similarly, South Australia has some of the largest temperate seagrass ecosystems in the world with over 5,200 square km of seagrass meadows. These meadows contain 22 (over one third) of the world’s estimated 60 seagrass species, of which Australia as a whole has about 30 species. furthermore, the majority of marine plants and invertebrates found in SA waters, are only found in the unique south.
As a result of SAs high levels of biodiversity and endemism of marine plants and invertebrates, we also have an incredible range of fish, sharks and rays in our waters.
Reefs, mangroves and seagrass meadows are particularly important as spawning and nursery areas for many species, and play an important part in sand retention. The loss of large areas of seagrass off the Adelaide metropolitan coastlinehas had major implications for the change in distribution of sand along the coast.
The marine environment of southern Australia – and the reef, mangrove and seagrass ecosystems in particular – provide many ecosystem services such as: food provision, nutrient recycling, oxygen production and gas exchange, pharmaceutical precursors, contributing to climate stability, preserving genetic diversity, and cultural, recreational and scientific significance.
It cannot be overstated how important and how special the southern temperate marine environment is. However, we know so little of how the marine ecosystems in this region function that management options and decisions are difficult to determine. Wwe are coming to understand more about both the environments themselves and the impacts of human activities, such as increased land-based sediment loads, nutrient enrichment, increased fishing activity and climate change, but there is still much more to learn and do.
If a species becomes extinct, or numbers are drastically changed in an ecosystem the effects can often be felt across the whole system. Ffor example, the loss of a top predator species such as blue groper in a reef system may lead to a population explosion in the species they would normally prey upon such as sea urchins and abalone. This in turn can lead to overgrazing of reef macroalgae (seaweed), changing the nature of the reef habitat. A habitat changed in this way will support a different and reduced range of species, which can in turn impact on species in other areas. A ‘chain’ or ‘domino’ effect is produced - the loss of one species can lead to the loss of many more with implications for ecosystem health and subsequently human use and enjoyment of the marine environment.
Action is needed now if this is to be avoided.
