Swamps, sweeps and salt lakes Wetlands
Covering more than 200 hectares, the Salt Lakes on Rottnest Island are just one part of this unique wetland habitat
Hear all about it!Rottnest’s wetland system is made up of salt lakes, brackish (slightly salty) swamps, and small freshwater holes or wet spots called seeps. The wetlands are fed by rainfall and groundwater coming to the surface from the underground aquifer.
Rottnest has a system of salt lakes which covers 10% of the Island at more than 200 hectares. There are 12 lakes in total with seven being permanent, while parts of the wetlands and 5 of the salt lakes dry up in summer. The levels of salt in the lake water can vary enormously but on average the salinity is about four times higher than sea water. Rottnest’s salt lakes support lots of plant life which are adapted cope with high levels of salt. The Samphire communities are found edging the Rottnest salt lakes. They are made up of plants of the Samphire species such as the Beaded Samphire and the Shrubby Samphire. The Coastal Bonefruit, Grey Saltbush, Shrubby Saltbush, Cockies’ Tongue and Coastal Pigface grow beyond the high water mark. The Sedge species is found the furthest back from the water.
Seeps are small freshwater holes or wet spots which are fed from springs supplied with water from the underground aquifer (water table). The freshwater seeps are the breeding ground for Rottnest’s three unique frog species and supply moisture to a whole range of plants. The swamps are fed by rain water and ground water and keep their moisture all year round. The plants that grow around them are mainly from the sedge species. Other species include the Beaded Samphire, Grey Saltbush and Shrubby Samphire which grow around the more salty margins.
The wetlands are very important as they support all of the ecosystems on Rottnest Island. Up to 19 freshwater and saltwater invertebrate families live in the wetland system and these provide food for Rottnest’s reptiles, amphibians, birds and mammals. The wetlands also provide vital water and food for migratory shorebirds, including over 1% of the world’s population of the Banded Stilt.
Listed as ‘Wetlands of National Importance’ under the Directory of Important Wetlands in Australia. The Island’s wetland system is represented in every category within the directory from highly saline (very salty) to fresh.
BirdLife WA has been surveying migratory birds at Rottnest Island since the late 1970s, providing significant data which has led to the recognition of the Island as a Wetland of National Importance in 1993 and as an Important Bird Area for seabirds in 2005.
The salt lakes also come under the listing of ‘Wetlands of National Importance’ by the Directory of Important Wetlands in Australia.
The Subtropical and Temperate Coastal Saltmarsh Ecological Community (which form part of the salt lakes ecosystem) has been listed as ‘Vulnerable’ under The Environment Protection and Biodiversity Conservation Act 1999.
Rottnest’s microbialite communities are listed as Priority Ecological Communities (PEC) under The Wildlife Conservation Act 1950.
- Extinct in Wild
- Critically Endangered
- Near Threatened
- Least Concerned
Do use water wisely on the island
Do keep to marked paths
Do dispose of your litter correctly
Hey there! Did you know...
The pinkish colour of the smaller lakes is partly caused by the algae Dunaliella salina. It contains a naturally occurring pink substance called beta-carotene. When the shrimp eat these algae, it gives them a red colour too! You can spot the samphire community in the “pink zone” of the lakes.