South Australia's unique marine environment supports a rich diversity of habitats, plants and animals.

In our cooler southern waters, long sandy beaches with rocky reefs and coastal cliffs prevail. The calm waters of our gulfs are home to large areas of seagrass, saltmarsh and mangroves. These are some of the largest, sheltered coastal ecosystems to be found anywhere in Australia.

South Australian waters boast many unique species of marine life. This uniqueness has come about because of Australia’s separation from other landmasses for millions of years, and the differences in water temperature between northern and southern Australia. The region has remained in relative isolation, geographically and climatically. In addition, many southern Australian species disperse over relatively short distances so they rarely interbreed with other populations.

Our temperate rocky reefs and seagrass meadows support a variety of fish, many of which are endemic to Australia. Over 400 species of fish are recorded in South Australian waters with a number of these species listed as protected.

In addition to creatures, native vegetation is also an important part of a marine ecosystem. The southern Australian coastline supports one of the largest numbers of marine flora, with over 1100 species of red algae alone, 25% of the world total, 75% of which are endemic.

Well over 6000 marine invertebrate species, are recorded for South Australia. Southern reefs and sponge gardens contain a great diversity of species, many of which are found nowhere else in the world. Up to ninety percent of many of the marine animal groups found in Southern Australia are endemic. For example up to 90 % of southern of sea squirts and lace corals or sea mosses are endemic. As with our marine plants there may be hundreds of plants still to be discovered or described. Even less is known about the microscopic plankton that form the basis of the marine food chain.

Threats to Our Marine Environments

Much of the pressure on the coast, our reefs and seagrass meadows comes from population growth along the coastal fringe.

Many Australians live on the coast, and as our towns, cities, farmlands and industries have spread many of our aquatic areas have been damaged or changed.

The loss of habitat has been one of the most significant factors affecting our marine environments and fisheries. With more and more people there are also more and more pressures on our coasts and marine life. Counting the major coastal cities, close to nine out of ten Australians now live in coastal zones. With the increase in population comes the inevitable human impacts which include:

• Coastal urban and industrial development has resulted in sewage discharges, contaminated stormwater and soil run-off and, industrial waste discharges. Nutrients can cause algal growth on corals and rocky reef organisms which smother them.
• Tourism developments such as the construction of resorts and marinas, siting pontoons and providing transport infrastructure, as well as increased fishing and diving.
• Impacts of nutrient loading from rural activities (fertiliser use), and poor catchment management, shipping and dredging which may create sediments which smother reefs and seagrass meadows.
• Environmental impacts from shipping and port activities such as the operational and accidental discharges of oil from vessels.
• Boat anti-fouling paints are known to affect shellfish populations.
• Impacts of fishing. Overfishing can remove the top order predators and some important grazing fish that are essential for healthy reef systems. Some fishing practices can physically damage reefs or seagrasses.

What you can do?

Generally –

• Prevent stormwater pollution. Stormwater is discharged untreated into our rivers and the sea. Common causes of stormwater include litter, garden waste such as leaves and grass clippings, pesticides and fertilizers, animal faeces, chemicals such as detergent and oils.
• Buy Organic, responsible farming can save our seas.Pesticides and fertilisers used in commercial farming inevitably make their way into our oceans through river and stream catchments.
• Know the fish you buy. Eat ‘low on the food chain’. Try to avoid eating species that are long lived and slow growing.
• When at the beach, try to walk around plants and animals along the shoreline.
• If you see litter on the beach pick it up.
• Leave shells where you find them so that they can become homes for other creatures

Boat owners and recreational fishers -

• Avoid anchoring boats within marine reserves. Boat anchors can be particularly damaging to reefs and seagrass meadows and our heritage shipwrecks.
• Stow your rubbish, don't throw it. Plastic, ropes and fishing tackle can injure and kill marine life. Dumping rubbish at sea is illegal.
• Please take care with liquid wastes such as detergents, fuel and oil, and sewage. These can be toxic to marine life.
• Contact your local port or marina and inquire whether they have adequate waste reception facilities.
• Catch only what you need and never take undersized creatures.